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Download Hi-Res ImageDownload to MS-PowerPointCite This:J. Phys. Chem. C 2021, 125, 9, 4955-4967
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Probing and Interpreting the Porosity and Tortuosity Evolution of Li-O2 Cathodes on Discharge through a Combined Experimental and Theoretical Approach

  • Amangeldi Torayev
    Amangeldi Torayev
    Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
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  • Simon Engelke
    Simon Engelke
    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
    Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, U.K.
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  • Zeliang Su
    Zeliang Su
    Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
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    Orcidhttp://orcid.org/0000-0001-7142-8977
    • , 
  • Lauren E. Marbella
    Lauren E. Marbella
    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
    Department of Chemical Engineering, Columbia University, 500 W 120th St, New York, New York 10027, United States
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    Orcidhttp://orcid.org/0000-0003-1639-3913
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  • Vincent De Andrade
    Vincent De Andrade
    X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont 60439, United States
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  • Arnaud Demortière
    Arnaud Demortière
    Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
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    Orcidhttp://orcid.org/0000-0002-4706-4592
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  • Pieter C. M. M. Magusin
    Pieter C. M. M. Magusin
    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
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    Orcidhttp://orcid.org/0000-0003-1167-3764
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  • Céline Merlet
    Céline Merlet
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    CIRIMAT, Université de Toulouse, CNRS, Bât. CIRIMAT, 118, route de Narbonne, Toulouse cedex 9 31062, France
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    Orcidhttp://orcid.org/0000-0003-3758-273X
    • , 
  • Alejandro A. Franco
    Alejandro A. Franco
    Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    Institut Universitaire de France, 103 Boulevard Saint-Michel, Paris 75005, France
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    Orcidhttp://orcid.org/0000-0001-7362-7849
    • , and 
  • Clare P. Grey*
    Clare P. Grey
    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
    ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    *Email: [email protected]
    More by Clare P. Grey
    Orcidhttp://orcid.org/0000-0001-5572-192X
Cite this: J. Phys. Chem. C 2021, 125, 9, 4955–4967
Publication Date (Web):February 25, 2021
https://doi.org/10.1021/acs.jpcc.0c10417
Copyright © 2021 The Authors. Published by American Chemical Society
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Abstract

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Li-O2 batteries offer a high theoretical discharge capacity due to the formation of light discharged species such as Li2O2, which fill the porous positive electrode. However, in practice, it is challenging to reach the theoretical capacity and completely utilize the full electrode pore volume during discharge. With the formation of discharge products, the porous medium evolves, and the porosity and tortuosity factor of the positive electrode are altered through shrinkage and clogging of pores. A pore shrinks as solid discharge products accumulate, the pore clogging when it is filled (or when access is blocked). In this study, we investigate the structural evolution of the positive electrode through a combination of experimental and computational techniques. Pulsed field gradient nuclear magnetic resonance results show that the electrode tortuosity factor changes much faster than suggested by the Bruggeman relation (an equation that empirically links the tortuosity factor to the porosity) and that the electrolyte solvent affects the tortuosity factor evolution. The latter is ascribed to the different abilities of solvents to dissolve reaction intermediates, which leads to different discharge product particle sizes: on discharging using 0.5 M LiTFSI in dimethoxyethane, the tortuosity factor increases much faster than for discharging in 0.5 M LiTFSI in tetraglyme. The correlation between a discharge product size and tortuosity factor is studied using a pore network model, which shows that larger discharge products generate more pore clogging. The Knudsen diffusion effect, where collisions of diffusing molecules with pore walls reduce the effective diffusion coefficients, is investigated using a kinetic Monte Carlo model and is found to have an insignificant impact on the effective diffusion coefficient for molecules in pores with diameters above 5 nm, i.e., most of the pores present in the materials investigated here. As a consequence, pore clogging is thought to be the main origin of tortuosity factor evolution.

Introduction

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Lithium oxygen (Li-O2) batteries are potentially game-changing energy storage systems with a very high theoretical capacity, (1) but they face a wide spectrum of very significant material challenges that need to be overcome before achieving commercialization. (2) A Li-O2 battery consists of a lithium-containing anode (typically Li metal), a separator soaked with an ionically conducting but electronically insulating electrolyte-containing lithium ions (Li+), and a porous electronically conducting cathode (typically a porous carbon) in contact with oxygen gas. During discharge, lithium is oxidized at the anode and lithium ions migrate to the cathode where they react with oxygen (dissolved in the electrolyte) to form solid discharge products, predominantly Li2O2 (lithium peroxide). During charge, Li2O2 discharge products decompose and form Li+ and O2. The lithium ions migrate back to the anode where they are reduced. Oxygen molecules are released back to the oxygen gas source. The predominant discharge product, Li2O2, is an electronic insulator. (3) During discharge, Li+ reacts with O2 to form LiO2 (lithium superoxide) close to the cathode surface. LiO2 can then form Li2O2 via further electrochemical reduction or through disproportionation. The growth of Li2O2 can be further divided into two processes. (4) If the intermediate species, LiO2, is insoluble in the electrolyte, it is either directly reduced or it disproportionates to form a film of Li2O2 on the cathode surface. The thickness of this film is limited by the electron tunneling through Li2O2 leading to thin films of about 10 nm. (5) If the solubility of LiO2 in the electrolyte is high, LiO2 molecules can diffuse away from the carbon surface forming large, toroidal-shaped discharge products via a disproportionation mechanism, which leads to pore clogging and impedes further transport of mobile molecules and ions in the electrolyte. (6−8)
In a Li-O2 cell, even though the active cathode (or positive electrode) material is oxygen, additional material is used to provide electronic conductivity and mechanical support to host the Li2O2 discharge products. This support structure is typically a porous carbon and is also designated as being a part of the cathode, although in principle it is not electrochemically active. The choice of carbonaceous cathode material and its structure has a large impact on the performance of the cell. There are two main capacity-limiting processes associated with the carbon cathode mesostructure. The first one is the passivation of the carbon surface area with electronically insulating discharge products, (9−12) and the second one is the slow transport of reactants, particularly oxygen, through the porous network. (13−16)
The passivation issue has been demonstrated at the experimental level in several studies as follows: Laoire et al. (9) studied it through cyclic voltammetry and rotating disc electrode characterization and Albertus et al. (10) through a combination of experimental and modeling techniques. One approach to mitigate passivation is to use a cathode with an extremely high surface area such as graphene-based (17,18) or nanostructured electrodes. (19) Another strategy is to avoid the formation of passivating thin films by preferentially forming large discharge products through dissolution of the intermediate species. Selecting electrolyte solvents with high donor numbers (20−23) or choosing specific salt anions (24) can enhance the solubility of these intermediate discharge products and lead to large discharge product particles. Adding a small amount of water (25,26) or redox mediators (27−29) can also lead to the formation of large discharge product particles. While all of these methods reduce surface passivation, the formation of large discharge product particles often clogs the cathode pores, introducing new issues for reactant transport during electrochemical charge and discharge.
Transport limitations arise from a combination of the slow diffusion of oxygen and Li+ in the electrolyte and the tortuous nature of the porous cathode. Using electrolytes with high oxygen diffusion coefficients, (30,31) and designing cathodes with high porous volume, and short and numerous diffusion pathways (32−34) can help in obtaining better battery performance. Regardless of the type of cathode mesostructure selected, the porous medium changes along discharge due to the formation of solid discharge products: some pores get smaller and some pores get clogged, impeding the transport processes (13−16) and motivating studies to investigate how the porous media change along discharge.
Bardenhagen et al. (14) investigated pore clogging for three gas diffusion electrodes along discharge using a three-electrode electrochemical impedance spectroscopy setup. They identified four processes with different time constants, which they attributed to lithium ion migration through a surface layer, charge-transfer from the carbon to the molecular oxygen, lithium and oxygen ion diffusion toward the cathode surface, and lithium ion movement inside the pores. Their observations confirmed that the pore clogging is a key limiting factor. In addition, they studied xerogel electrodes and showed that they provide high capacities due to the large volume of mesopores allowing for an improved oxygen transport.
To improve the battery performance, studies that directly investigate the transport properties, particularly tortuosity factor of the electrodes, are needed. Here, we present a work that focuses on the tortuosity factor evolution along discharge and investigate how it is affected by the type of electrolyte used. For this purpose, pulsed field gradient nuclear magnetic resonance (PFG-NMR) experiments are used. PFG-NMR spectroscopy represents a powerful tool to measure diffusion of mobile species in porous media, which has been used to study ion transport in batteries and supercapacitors. (35,36) Forse et al. studied the effect of the pore size distribution on the self-diffusion of ions and measured diffusion in and out of the nanopores in YP50F and YP80F, two porous carbon materials used in supercapacitors. 1H, 19F, and 13C NMR experiments were conducted. (35) It was shown that the diffusion of ionic species is more than two orders of magnitude slower in nanoporous materials compared to diffusion in the bulk electrolyte. The ionic concentration, which changes along charge and discharge in the supercapacitor systems, also influences diffusion. Engelke et al. (36) used 1H and 7Li PFG-NMR to measure anisotropic diffusion in model porous silicon substrates. They measured effective diffusion coefficients with incremental diffusion times, which allowed them to calculate the related mean square displacements and extract information about the pore dimensions. Stallmach et al. (37) and Kondrashova et al. (38) studied anisotropic self-diffusion in nanoporous materials to analyze orientation-dependent diffusivities, monitoring and quantifying diffusion of probe molecules along one-dimensional channels.
In this work, we use 1H PFG-NMR to study the tortuosity factor evolution when discharging Super P cathodes in Li-O2 batteries. We focus on long-range diffusion and measure effective diffusion coefficients of tetraglyme molecules in cathodes at different states of discharge. The tortuosity factor is computed from the ratio between the measured effective diffusion coefficient in the porous medium and the bulk diffusion coefficient. To study the effect of the solvent, we conduct experiments with two different electrolytes consisting in LiTFSI dissolved in either tetraethylene glycol dimethyl ether (tetraglyme) or in dimethoxyethane (DME). The tortuosity factor measurements are compared to tomographic imaging experiments on the discharged samples. To help interpret the experimental observations, we investigate the effect of pore sizes, and pore clogging, on the tortuosity factor, using a kinetic Monte Carlo (kMC) model and pore network model (PNM), respectively, as described in previous publications. (39,40)

Methodology

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Cell Components Preparation

Anode

A lithium metal anode is used in the eight cells of this study. The lithium anode is cut in a disk shape with a 0.73 mm thickness and 9 mm diameter. Considering that the density of lithium metal is 0.534 g cm-3, this negative electrode is sufficient to provide a capacity of about 95.8 mA h (7725 mA h g–1, normalized to cathode mass) per cell, which ensures that the anode is not a capacity limiting parameter, as none of the cells reached this high discharge capacity.

Separator

Two layers of Whatman glass fiber with a diameter of 14 mm are used in each cell. The total thickness of these two layers is about 1 mm. Two layers are used to avoid any short circuit in the cell assembly.

Electrolyte

Two different solvents are used, dimethoxyethane (DME, anhydrous 99.5%, Sigma-Aldrich) and tetraethylene glycol dimethyl ether (tetraglyme, 99%, Acros Organic). LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, Sigma-Aldrich) was used as a salt. Before use, the salt was dried in a vacuum oven at 120 °C overnight and transferred into an argon glovebox.

Cathode

Self-standing mesoporous Super P carbon electrodes were prepared from a mixture of 70% (mass percentage) Super P carbon (TIMCAL) and a 30% PTFE (polytetrafluoroethylene) binder in ethanol. The mixture was agitated using magnetic stirring at 70 °C for about 2 h, and the resulting paste was rolled into an approximately 300 μm thick film. The film was cut into electrodes with diameters of 11 mm. After initial drying of the electrodes in a 50 °C oven under ambient air, they were further dried under vacuum at 120 °C for 12 h. The dried electrodes were taken into an argon gas glovebox without air exposure and then used to make batteries. The mass loading of the electrode is around 13.0 ± 0.4 mg cm–2 (around 9.1 mg cm–2 of carbon mass loading, 70 wt%). The discharge capacities reported in this article are normalized by the total electrode mass (12.4 mg: mass of binder + carbon).

Electrochemical Testing and Sample Preparation for PFG-NMR and Tomography

For the electrochemical experiments, Swagelok cells are used (Figure 1a). A hole was drilled through the plunger at the cathode side to connect to the oxygen supply. A lithium metal anode, two layers of separators, and a cathode were placed into the cell; then 250 μL of electrolytes was added. The cell was assembled in an argon glovebox and put into an airtight glass chamber (Figure 1b). Once the glass chamber was sealed, it was taken out of the glovebox and flushed with oxygen gas for 5 min to replace the argon gas with oxygen. After flushing and before the electrochemical tests, the cell was rested for 6 h to give a sufficient time for oxygen molecules to dissolve in the electrolyte.

Figure 1

Figure 1. (a) Scheme of the Swagelok cell used for the electrochemical experiments. (b) The glass chamber used to keep the Swagelok cells under oxygen, which has space for a single Swagelok cell.

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The electrochemical tests have been carried out on a Bio-Logic VMP3 multichannel potentiostat. Four cells with 0.5 M LiTFSI in tetraglyme and four cells with 0.5 M LiTFSI in DME electrolytes were discharged galvanostatically with a current of 50 μA. The discharge process was stopped at different depths of discharge for the different cells, the Swagelok cells were disassembled, and the cathode mesostructures were analyzed by PFG-NMR (two cells discharged with tetraglyme and four cells discharged with DME electrolyte solvents) experiments and tomography (two cells discharged with the tetraglyme electrolyte solvent). When disassembling the cells, precautions were taken so that all measurements were conducted on samples that had not been exposed to air. After discharge, the cells were disassembled in a glovebox, and each cathode was put in a vial with pure DME to remove the salt and electrolyte. DME was used to wash out the salt because of its low viscosity and because it evaporates easily.
For the PFG measurements, the cathode was dried in the prechamber of the glovebox under vacuum. The dried electrode was then placed in another vial with pure tetraglyme. The vial with the tetraglyme-soaked electrode was put under vacuum for 3 min to remove gases inside the pores and help with the wetting of the small pores by the solvent molecules; the electrode was left to soak in the solvent for 1 h. After that, the electrode surface was gently dried on a lab paper-towel (as discussed below) and the electrode was put into a sealed plastic bag (Figure S1).
For the tomography experiments, the electrodes were transferred after washing with DME into an argon-filled glove-bag with an optical microscope for further sample preparation. The electrodes were chopped into small pieces. Thereafter beneath the microscope, one was selected, with the aid of a microcontroller and epoxy, a piece that fills the field of view (55 μm) of the transmission X-ray microscope. The mounted sample was inserted with care into a Kapton tubing and sealed by Torr Seal curing at 50 °C overnight to avoid humidity contamination of the Li2O2 particles.

PFG-NMR Experiments

Pulse Sequence and Theory

For diffusion NMR studies, the position of a nucleus is typically encoded by applying a linear magnetic-field gradient along the magnetic field axis, ΔB(gz) = gzz, superimposed on the static homogeneous magnetic field B0. In this work, the so-called STimulated-Echo (STE) pulse sequence 90°-τ–90°-τ′-90°-τ–acquisition combined with magnetic-field gradient pulses (Figure 2) was employed. The STE pulse sequence works well for NMR nuclei with transversal-relaxation times shorter than spin–lattice relaxation times, as is typically the case for molecules with slow or restricted mobility.

Figure 2

Figure 2. Pulse sequence used for the stimulated echo-pulsed field gradient NMR experiments: (top) NMR frequency pulses and (bottom) gradient pulses.

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For a linear magnetic field gradient gz along the magnetic field axis, the total magnetic field experienced by the observed NMR nuclei is(1)After the initial 90° radio frequency (rf) pulse, a magnetic-field gradient pulse of duration δ is applied to encode the NMR coherences with the locations of the molecules in the system. The second 90° pulse at time τ stores this encoded coherence along the magnetic field axis. Then, the molecules are given a certain time τ′ to diffuse before the final 90° pulse followed by another gradient pulse (equal to the first) is applied to decode the location tags. The three rf pulses combined with the gradient pulses produce a stimulated-echo signal at time t after the last pulse.
The idea behind this pulse sequence is that if molecules do not move at all during Δ (the diffusion time between the two gradient pulses, approx. τ + τ′, Figure 2), the encoding and decoding magnetic fields will be the same and the echo intensity of the (stimulated) echo signal for these molecules will be maximal. By contrast, if molecules diffuse during the pulse sequence, then they will experience different magnetic encoding and decoding fields. Consequently, the intensity of the echo signal will decrease. An effective diffusion coefficient (Deff) can be determined by applying a range of gradients for a fixed value of Δ and subsequently fitting the signal intensity I′ as a function of gradient strength gz to the Stejskal–Tanner equation (see Figure S2). (41) For the PFG stimulated echo experiment with the pulse sequence depicted in Figure 2, the equation is(2)where γ is the gyromagnetic ratio of the observed NMR nuclei, typically 1H. (41,42) In practice, to avoid gradient-ringing effects, trapezoid-shaped gradient pulses were used. Any remaining coherence not stored along the magnetic field axis by the second 90° pulse was suppressed by the spoil pulse.
For the pure tetraglyme measurement (bulk diffusion), the diffusion time Δ selected in the PFG-NMR experiment does not affect the diffusion coefficient as the diffusing molecules are not restricted in their motion. For the diffusion in porous media, the diffusion time plays an important role. If the diffusion time is too short, then, the diffusing molecules will not encounter any pore walls, and the calculated diffusion coefficient will be similar to the bulk diffusion coefficient. When increasing Δ, the mobile molecules will diffuse further and collide with pore walls (Figure 3a). Hence, the effective diffusion coefficient will decrease (Figure 3b). For sufficiently large diffusion times, the confined diffusion coefficient converges to a value corresponding to long range diffusion, which is the one suitable for extracting the tortuosity factor. The NMR technique used here is not spatially resolved, and in a Li-O2 battery, the discharge products can have non-uniform distribution along the electrode thickness due to slow oxygen transport. A low discharge current density has been used to minimize this effect.

Figure 3

Figure 3. (a) Illustration of the area covered by a diffusing molecule with time. (b) Schematic representation of free diffusion and confined diffusion as a function of diffusion time.

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Relation between the Tortuosity Factor and Diffusion Coefficients

The porosity of an electrode is the fraction of the void (pore) volume in the total electrode volume. The tortuosity factor is a measure of the geometric complexity of a porous medium, and it is usually defined as the squared ratio between the curved paths followed by a fluid in the porous medium over a straight path. The porosity and tortuosity factor both affect the effective diffusion coefficient in a porous electrode. When there is a more porous volume (high porosity), then, the diffusion is less restricted, so the porosity and effective diffusion coefficients are positively correlated with each other. When the tortuosity factor increases, the diffusion paths of the mobile species are more curved, and their effective diffusion coefficients decrease. Hence, the tortuosity factor and effective diffusion coefficients are anticorrelated. Following these intuitive considerations, the tortuosity factor (τ) is defined with respect to the effective diffusion coefficient (Deff), the bulk diffusion coefficient (D0) and the porosity (ε) as (43)(3)By knowing D0 and Deff, one can calculate .
In this work, the porosity and tortuosity factor are considered to be a reflection of the structural properties of the carbon cathode. That is, they mainly depend on the porous medium and its mesostructure and not on the nature of the diffusing species, implying that the diffusing species do not bind to the carbon mesostructure, or that the nature of the interaction does not vary between different solvents. Different molecules or ions will not necessarily experience the same porosity and tortuosity factor in a given medium. For example, if molecule B is twice as big as molecule A, some parts of the porous electrode might not be accessible to B due to its size, and as a result, a smaller effective porosity and larger tortuosity factor will be determined when using B as a probe. The porosity and tortuosity factor might also depend on the rigidity/flexibility of molecules A and B. In practice, however, the size differences between relatively similar molecules, e.g. the different solvents used in Li-O2 batteries electrolytes, are limited, and for the purpose of the current work, it is possible to assume that the porosity and tortuosity factor measured with these molecules reflect conditions experienced by typical battery electrolytes inside the carbon structure. The measurements require a molecule with the appropriate diffusion coefficient and relaxation time to sample the different pores and move a sufficient distance within the timescale of the PFG-NMR experiment; here, the motion of 1H nuclei in the tetraglyme solvent was tracked by NMR. It is worth noting that oxygen molecules cannot be probed directly using 17O NMR due to the paramagnetic character of O2 and the low natural abundance of 17O. As the oxygen molecules are dissolved in the electrolyte, we assume that the effect of confinement on these molecules will be similar to the one on the solvent molecules.

Experimental Details

A 300 MHz Avance III Bruker NMR spectrometer equipped with a gradient amplifier, Diff50 gradient stack, and a 10 mm 1H coil configuration was used for the 1H PFG NMR experiments. 90° pulses of 14.7 μs, a (half-height) gradient duration δ of 1 ms, and a time τ between the first two pulses of 1.5 ms were employed. The overall diffusion time Δ ≈ τ + τ′ was varied between 10 and 1200 ms. The gradient amplitude gz was varied between 0 and 200 G cm–1 (calibrated versus the self-diffusion coefficient of neat water, 2.20 10–9 m2 s–1, at 25°C). The STE was recorded in the time domain for 16 different gradient values. PFG-NMR measurements were conducted as described above with a varying diffusion time. For the long-range effective diffusion coefficients, the PFG-NMR measurements with diffusion time 1200 ms are used. The NMR experiments are carried out at 25°C with temperature controlled with water flow.
The STE signals were then transformed into the frequency domain, the resulting NMR peaks integrated, and the peak integrals plotted as a function of the gradient value. NMR data processing is done within the Bruker NMR software Topspin to extract intensities. Further analysis and fitting of intensities to the Stejskal–Tanner equation are done with MATLAB software.

Tomographic Imaging

An X-ray nano-tomography experiment with 54 nm spatial resolution (voxel size 54 nm) was done using 50 nm outermost zone width Fresnel zone plate optics and was performed in 32-ID-C in the advanced photon source (APS) synchrotron at Argonne National Laboratory. (44) A Beam Shaping Condensor of a 60 nm outermost zone width was used. The in-line Zernike phase contrast technique involving a phase ring in the back focal plane of the zone plate was used to increase the contrast between carbon and lithium peroxide. (45) Measurements were performed at 8 keV with a monochromatic beam (ΔE/E = 10–4). The distance sample to detector of 3329 mm provided an X-ray magnification of 46. Projections of 721 were acquired within 180° (0.25°/frame and 1 second per frame) rotation with a FLIR GS3-U3-51S5M-C detector. Projections were preprocessed with packages present in Tomopy (46) and then reconstructed into volumes by the GPU-accelerated SIRT method (47) (200 iterations, more iterations induce noises) in the same library. The WEKA trainable segmentation Fiji plug-in Random Forrest based machine learning was used for the multiphase segmentation. (48) The surface, porosity, and tortuosity factor determinations are conducted respectively with in-house codes developed by the authors (39) and Taufactor; (49) Taufactor calculates the tortuosity factor from the tomographic images, simulating diffusion by solving Fick’s second law. (49)

Pore Network Model

To assess the effect of the discharge product growth mechanism on pore clogging, a pore network model already described in previous publications was used. (39,40) The galvanostatic discharge potential profiles (the discharge current density is 100 μA g–1) for a Super P pristine electrode mesostructure obtained via tomographic imaging were simulated. (39) A tomographic image of the pristine Super P electrode from our previous work (39) was used as we do not have the tomographic image for the pristine electrode used in this work. As the tomographic image in our previous work and the current study use the same Super P material from the same supplier, their microstructure should have a similar morphology. A system size of 4 × 4 × 5 μm, along two radial and the electrode thickness directions, respectively, was used. In the model, an overall electrochemical reaction is considered where two lithium ions react with an O2 molecule to form Li2O2. Five simulations were completed on the same starting electrode mesostructure with five different escape factors (χ = 0, 0.25, 0.5, 0.75, and 1) to study the effect of the discharge particle growth mechanism on the pore clogging and tortuosity factor evolution. The escape factor represents the propensity of LiO2 intermediate molecules of the discharge process to dissolve in the electrolyte and contribute to the growth of large discharge particles. By increasing the escape factor from 0 to 1, we move from a thin-film growth to a solution phase growth mechanism (and the formation of large particles).

Kinetic Monte Carlo Model

To study the effect of pore size and the importance of the Knudsen diffusion effect in the systems explored here, we developed a kinetic Monte Carlo model. The Knudsen effect describes the diffusion in narrow pores where the diffusion coefficient is affected by collisions of the mobile species with the pore wall. While intuitively, smaller pores will lead to more collisions and slower diffusion, a model was constructed to obtain quantitative information on this effect for the pore sizes relevant to this study. The kMC model is adapted from a previously published model, which had been used to simulate the discharge process in Li-O2 batteries. (50)
A cylindrical pore geometry (Figure 4) was used to simulate diffusion in a pore. The pore volume was sliced into voxels with a side length of 0.5 nm, which is assumed to be the hydrodynamic size of a dissolved O2 molecule. The hopping frequency (γi), also called the event frequency, was calculated as(4)where DO2 is the bulk diffusion coefficient of O2, and s is the voxel size. In the model, the O2 molecules can jump (or diffuse) to 18 sites (6 face sharing and 12 edge sharing) provided that those neighboring voxels are empty. Periodic boundary conditions in the direction of the pore length were used.

Figure 4

Figure 4. Cylindrical pore geometry considered in the kMC model.

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In this kMC model, only translational motion and no reactions were simulated. A variable step size method is used (50) and the time step is calculated as(5)(6)where ρ1 is a random number in the interval (0,1], i.e., larger than zero and smaller or equal to one, γtot is the sum of all event frequencies, and N is the total number of possible events.
The event occurring at a given step is chosen according to the weighted probability of each event. The event j is selected according to the following rule(7)where ρ2 is a random number in the interval (0,1]. This process allows for the simulation of a system with various event frequencies, including a mixture of fast and slow events. In the present case, only events related to the transport of a single type of molecule (O2) are considered. However, the script is written in a general form to be able to work with many event types if necessary.
It is worth noting that, in this work, an approach upgraded from the ones previously reported was used. (50,51) A simplified scheme of our algorithm is given in Figure S3. In this new scheme, all possible events at the beginning of the calculation are determined and then stored in an easy-to-update data structure. In the main loop, only the events, which are in the vicinity of the executed events, are updated. The number of events updated at each timestep is around 18 against several thousands when the full ensemble of possible events is scanned. As a consequence, this procedure is much more efficient, and calculations are much faster: the new procedure is about 2000 times faster than the previously reported ones (50,51) for the system under investigation here.
To extract the diffusion coefficients from the particles trajectories, the mean square displacement (MSD) method was used where the MSD function is defined as(8)where di, t is the position of molecule i at time t and di, t0 is the position of the same molecule at time t = 0. The ⟨.......⟩ sign corresponds to an average over all O2 molecules. After a long enough simulation time, the MSD curve becomes linear (Figure 5), and the diffusion coefficient (D) can be retrieved from its slope according to Einstein relation(9)

Figure 5

Figure 5. Illustration of the determination of a diffusion coefficient from an MSD curve. Two vertical lines show the time interval where the MSD curve is linear with time. The red line is the fit to the MSD curve in the selected region.

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For kMC simulations with different cylinder diameters, if the cylinder length was kept the same for all pore sizes, there would be a very significant variation in the number of oxygen molecules in the pores as cylinders with large diameters would contain many more molecules than cylinders with smaller diameters. This would affect the MSD fitting accuracies. To have the same amount of oxygen molecules in all the calculations, the porous volume is kept constant and equal to 783,398 nm3 (i.e., 6,267,184 voxels), which corresponds to the pore volume of a cylinder with a diameter of 100 nm and a length of 100 nm. This means that cylinders with smaller pore diameters will have larger pore lengths. The amount of oxygen in each calculation is set to 1256 molecules. The total simulation time is 2 μs.

Results and Discussion

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Measurement of Bulk Diffusion Coefficients and Evaluation of Drying Procedures

The bulk diffusion coefficient in the pure tetraglyme solvent (i.e., the value measured under nonconfined conditions) was first measured via 1H PFG NMR spectroscopy and determined to be 3.420 10–10 m2 s–1, with a 95% confidence range of ±0.005 10–10 m2 s–1 (i.e., a 0.14% error bar; see Figure S2 for details). To measure the diffusion of tetraglyme confined in the porous structure of a Super P electrode, it is important that all the solvent molecules are inside the porous structure and that there are no molecules on the surface of the electrode since the latter will have larger effective diffusion coefficients than the confined ones and will affect the average measured diffusion coefficient. Two different drying approaches were tested. For the first one (the gently dried method), the soaked electrode is gently touched and wiped on both sides using a lab paper-towel. For the second drying approach (termed thoroughly dried), the gently dried electrode is put on a lab paper-towel and another piece of paper-towel is put on top of it. Then, a slight pressure was applied by hand to soak away any remaining liquid on the surface. 1H NMR spectra were acquired from samples prepared via the three approaches and used to estimate the relative solvent quantities (Figure S4) and show that the free electrolyte (sharp) signal was removed even after gently drying. Thoroughly drying removed further a 45% of the total solvent. Diffusion coefficient measurements on electrodes dried with the two techniques were then compared with results from two other samples: bulk tetraglyme; an electrode flooded with an excess of the tetraglyme solvent and is shown in Figure 6.

Figure 6

Figure 6. Diffusion coefficients for bulk tetraglyme and tetraglyme in three Super P electrodes, determined with PFG methods as a function of diffusion time, Δ.

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Unlike the neat tetraglyme, for samples containing the porous electrode, the effective diffusion coefficient decreases as the diffusion time increases, which is a signature of confined diffusion (Figure 3). The similar diffusion coefficients obtained for the gently dried and thoroughly dried samples provide confidence that both approaches are sufficient to remove the excess liquid from the surface of the electrodes, consistently with the 1H NMR spectra of the solvents (Figure S4). If that was not the case, the diffusion coefficients for the gently dried case would be higher than the thoroughly dried case as demonstrated by the results for the flooded sample. Even though a significant amount of additional electrolytes was removed (45%) in the thoroughly dried sample (vs the gently dried sample), this did not result in any visible effects from restricted diffusion due to empty pores with no solvent, as the diffusion coefficients measured at longer diffusion times for the gently dried and thoroughly dried were essentially identical. For subsequent experiments, the gently dried approach was used.

Tortuosity Factor Evolution along Discharge

NMR

To study the tortuosity factor evolution along the depth of discharge, several self-standing Super-P electrodes were discharged at a discharge current of 50 μA. For the tetraglyme solvent, two electrodes are discharged: one cell is discharged to the end of capacity and the other is stopped halfway when a 253 mAh g–1 capacity is reached (Figure 7a). As there is some variability in the discharge capacity of Li-O2 batteries, the definition of “halfway” is only an approximation. (39,52) For the DME solvent, four electrodes are discharged, and the discharge processes are stopped at 73, 121, 243, and 647 mAh g–1, the last one being the end of discharge.

Figure 7

Figure 7. Tetraglyme diffusion in self-standing Super P electrodes as a probe for pore clogging at various states of discharge against lithium. (a) Constant 50 μA current discharge profiles of Super P with 0.5 M LiTFSI-tetraglyme as electrolyte. (b, c) Diffusion NMR of Super P electrodes discharged in (b) DME and (c) tetraglyme. 1H PFG NMR echo decays vs the composed experimental parameter γ2gz2δ2(Δ – δ/3) (eq 2) increasingly deviate from monoexponential behavior (dashed lines) at increasing depth of discharge. The data are well described in terms of a biexponential model (solid lines) with two discharge-constant diffusion coefficients and fractions, which vary with discharge. Phenomenologically, the two fractions represent the clog-free and clogged electrode parts. (d) Effective tetraglyme diffusion coefficients (a weighted average of the two diffusion coefficients) in self-standing Super P electrodes discharged with either DME or tetraglyme as electrolytes as a function of discharge. Dashed lines are a guide to the eye. The PFG NMR data shown here have been recorded for a diffusion time Δ = 1200 ms. For PFG echo decays at different Δ times, see Figure S5.

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All electrodes, whether discharged with tetraglyme or DME electrolyte, were dried and saturated with pure tetraglyme (without LiTFSI). Then, pore clogging was probed by measuring solvent diffusion at varied diffusion times in the range 20–1200 ms (Figure S5) using PFG NMR. Here, we focus on the data obtained with the longest diffusion time, Δ = 1200 ms where diffusion coefficients in pristine electrodes approach a convergence limit (Figure 6). The root-mean-square displacement <r2 >1/2 of bulk tetraglyme molecules indicates that electrolyte molecules travel approximately 50 μm in this time (<r2>1/2 = (6·D·t)1/2 = (6·D·Δ)1/2 = (6·3.42 10–10 m2 s-1·1.2 s)1/2 = 49.6 μm). This ensures that the diffusion coefficients do not measure local (i.e., short range) motions but correspond to long-range diffusion.
Figure 7b,c and Figure S5 show PFG echo intensities versus the composite experimental variable X = γ2gz2δ2(Δ – δ/3) (γ, gz, δ, and Δ defined in eq 2). The observed decays for discharged electrodes deviate significantly from single-component behavior (eq 2) and increasingly so as the depth of discharge increases. The fast decay components reflect relatively unrestricted solvent diffusion, whereas the slow decay components represent the confined diffusion in clogged parts of the porous electrode. This heterogeneity also arises because of the geometry of the lithium-oxygen battery, oxygen entering from one side of the electrode and Li+ ions from the other. All PFG curves for tetraglyme diffusion in the electrodes at varied diffusion times and different stages of discharge in DME or tetraglyme are well described by a biexponential function fAexp(-DAX) + fBexp(-DBX). To improve the consistency of the analysis, all curves obtained for the same diffusion time, but at different states of discharge, are fit in a combined manner. The specific fit procedure treats the two diffusion coefficients as independent of the discharge stage and allows the components amplitudes to vary freely. While it is a simplification to divide the pores into two categories, clog-free and clogged with fast and slow diffusion, respectively, the model works well in a phenomenological way and can be used to explore distributions in diffusion coefficients.
Pairs of tetraglyme diffusion coefficients (DA, DB) extracted for electrodes discharged in DME and tetraglyme, as a function of diffusion time are plotted in Figure 8. The coefficient DA of the mobile component decreases in both electrodes from close to the free tetraglyme diffusion value 3.5 10–10 m2 s–1 at short diffusion times toward 2.5 10–10 m2 s–1. This decrease likely indicates that even the mobile component in the largely un-clogged pores experiences diffusion restrictions at sufficiently long diffusion times. The DA decrease also reflects the continuous solvent exchange between clog-free and clogged parts of the porous network within the timeframe of the measurement (0–1200 ms). The second coefficient DB decays from ca. 1 10–10 to 0.51 10–10 m2 s–1 in the DME discharged electrode but is fairly constant around 1 10–10 m2 s–1 in the tetraglyme-discharged electrodes.

Figure 8

Figure 8. Diffusion coefficients pairs (DA, DB) extracted from bicomponent fits to PFG decays as a function of the diffusion time for an electrode discharged in DME (left) and tetraglyme (right). The biexponential model assumes that the values of the diffusion coefficients do not change with the discharge stage, but the relative fraction of each component does. Changes in pore clogging are reflected by the fraction of each component (Table 1).

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With the values of the diffusion coefficient pair (DA, DB) assumed independent of the discharge stage, the degree of pore clogging at varied discharge is reflected by the fraction fB (representing the volume fraction of clogged pore) of the relatively immobile or restricted diffusion coefficient (Table 1). The fraction fB in the bicomponent model generally increases with state of discharge, as expected, while for a given diffusion time fB, values are generally higher for the electrodes discharged in DME than in tetraglyme. Pore clogging thus appears to occur more frequently during discharge in DME. Interestingly, fraction fB decreases with the diffusion time indicating that the diffusion appears to be more homogeneous at longer diffusion times as a larger pore volume is sampled. This may at least in part be ascribed to continuous solvent exchange between clog-free and clogged parts of the porous network, an effect that becomes more pronounced as the diffusion time increases.
Table 1. Fraction fB of Immobile/Restricted Diffusion Component as a Function of Depth of Discharge and of the Diffusion Time, Tentatively Representing the Fraction of Clogged Pore Space
timedischarged in DMEdischarged in tetraglyme
0 mA h g–173 mA h g–1121 mA h g–1243 mA h g–1647 mA h g–10 mA h g–1253 mA h g–1454 mA h g–1
20 ms     0.160.360.32
50 ms0.190.160.350.220.35   
100 ms0.170.190.360.250.45   
150 ms     0.130.300.34
200 ms0.190.180.320.240.530.000.200.24
500 ms0.070.170.260.210.540.000.130.26
800 ms0.040.140.240.210.600.000.150.33
1200 ms0.000.190.220.200.650.000.130.36
The tortuosity model treats the porous network as homogeneous, whereas the bicomponent model artificially divides the pore network into two categories, clog-free and clogged pores. In reality, of course, various degrees of pore clogging may occur in different pores, and dynamic solvent exchange between clog-free and clogged pore areas may also reduce the contrast between these regions.
A possible link between the tortuosity model and bicomponent model can be established by deriving the weighted average diffusion coefficient Dav = fADA + fBDB from the bicomponent fit (Table S1). For the biexponential model used in our analysis, this corresponds to the initial slope of the decay. This represents an alternative way to characterize the PFG curves with a single effective diffusion parameter. The average diffusion coefficient DA is always lower than the free tetraglyme diffusion coefficient and generally decreases with discharge and the overall diffusion time, as expected. The weighted average diffusion coefficient from the biexponential model for a diffusion time of 1200 ms is shown on Figure 7d and can be compared with the monocomponent fitting shown on Figure S5. The diffusion coefficients have the same trends in both cases. However, the errors in the bicomponent fitting are significantly lower (the single-component fit showing errors as large as 60%, see the Supporting Information for the error analysis, and bicomponent fit leading to errors below 20%), supporting our analysis of the diffusion in terms of more than one diffusion coefficient. Our simple analysis considers two types of diffusion in the electrode: one in more restricted (clogged pores) and the other in less restricted (clog-free) porous domains. In reality, the electrode will have a distribution of diffusion domains with varying degrees of restriction (clogging).
The overall trend observed for both solvents is that the effective diffusion coefficient decreases as the cell is discharged further and the transport through the electrode becomes more tortuous. This is consistent with the growth of discharge products leading to a reduction of porosity via pore shrinkage and clogging of some pores. Higher effective diffusion coefficients are measured for the electrodes discharged in the tetraglyme-based electrolyte compared to the electrodes discharged in the DME-based electrolyte. This is ascribed to the larger particles formed and more pore clogging in DME: DME has a higher donor number than tetraglyme, and thus, we expect the corresponding cells to show larger Li2O2 particles than the tetraglyme ones. (22,23)
The evolution of the tortuosity factor can be calculated from the effective diffusion coefficients using eq 3. The porosity of the pristine electrode is 0.81, as calculated from the measured electrode dimensions and mass (see Table S2 in the Supporting Information). For this calculation, we assume that the only discharge product is Li2O2, which allows the volume of Li2O2 to be calculated from the discharge capacity and the change of porous volume, and porosity, to be estimated. The evolution of the tortuosity factor was then estimated via Bruggeman relation using eq 10(10)and compared with that obtained from the PFG data in Figure 9.

Figure 9

Figure 9. Tortuosity factors in pristine, partially, and fully discharged self-standing Super P electrodes, extracted from PFG-NMR measurements using weighted average diffusion coefficients from the biexponential model. The solvent used for discharge is indicated in the legend. The Bruggeman relation is applied by assuming that all discharge products are Li2O2. Dashed lines for experimental data are linear fit to the data points weighted with the error bars. An explanation of the error analysis is given in the Supporting Information.

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The tortuosity factor values extracted from PFG-NMR measurements for DME change more drastically than suggested by the Bruggeman relation, particularly for DME. (53) The tortuosity factor evolution depends on the porosities of the pristine and discharged electrodes, which are only estimated here. Thus, we have also plotted vs depth of discharge and is shown in Figure S6 since this does not require any assumptions concerning the change in porosity: it is simply the ratio of Deff/D0 (see eq 3). The plot shows the same trends as Figure 9, supporting our analysis of tortuosity vs depth of discharge.

Tomography

To measure the change of tortuosity factor with a second technique, tomographic imaging was conducted on two samples: partially (206 mAh g–1) and fully (362 mAh g–1) discharged Super P electrodes with 0.5 M LiTFSI in tetraglyme electrolytes. Tortuosity factor values of 4.95 and 5.4 are calculated from the tomographic images for partially and fully discharged cells, respectively. To compare them with the evolution of tortuosity factor values measured by PFG-NMR experiments, we compare the rate of change of the tortuosity factor, i.e., the slopes of the discharge capacity versus plots shown in Figure 9 (Table 2). Although the errors associated with the PFG measurements are large, which is largely ascribed to differences between cells, each ex situ PFG measurement was made on a different cell, and errors in the PFG measurements (as discussed above) associated with describing the PFG data with a single diffusion coefficient for the fully discharged sample, a significant difference is seen between the values calculated for the tetraglyme and DME-discharged electrodes. The tortuosity factor value evolution calculated from tomographic images for electrodes discharged with tetraglyme electrolyte is close to the value measured by PFG-NMR experiments for the same electrodes and very different from the electrodes discharged in DME-based electrolyte and the Bruggeman estimation.
Table 2. Rate of Change of the Tortuosity Factor along Discharge, Calculated with Three Different Techniques
sample and methodrate of tortuosity factor change along discharge × 10–4 (g m–1A–1 h–1)
Bruggeman relation2.00 ± 0.03
PFG-NMR tetraglyme7.5 ± 2.1
PFG-NMR DME16.6 ± 2.5
TXM tetraglyme5.9
The analysis of the tomographic images also allows us to extract pore size distributions, which show an overall increase in the fraction of smaller pores, suggesting a shrinkage of the pores (Figure 10). However, clogging of micropores with pore sizes below 54 nm is hard to evaluate solely by tomography measurements due to imaging resolution, and any analysis should be coupled with other techniques.

Figure 10

Figure 10. Pore size distributions obtained from tomographic images of (a) partially 206 mAh g–1 and (b) fully 362 mAh g–1 discharged Super P electrodes with 0.5 M LiTFSI, tetraglyme electrolytes at 50 μA discharge current.

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PNM Modeling

The PNM approach (39) was then used to explore the hypothesis that the formation of larger discharge particles leads to more pore clogging. In the PNM approach, the escape factor parameter, χ, can be varied to adjust the relative contributions of the film growth mechanism versus the particle growth mechanism. A larger value of χ corresponds to a more predominant particle growth mechanism and thus the formation of larger particles of Li2O2.
Figure 11 shows the evolution of the number of clogged pores along discharge for five different escape factors, the number of clogged pores being higher for larger escape factors. This calculation thus provides a plausible interpretation as to why the effective diffusion coefficients for electrodes discharged in DME-based electrolytes decreases faster along discharge. It is worth noting that there is a large difference between the curves for χ = 0 and χ = 0.25 but the changes are more limited for higher escape factors. This would indicate that even without being predominant, the onset of particle growth is enough to significantly enhance the pore clogging phenomenon. Indeed, as shown in Figure S7 (the gradient in discharge products is shown in Figure S8), already for χ = 0.25, a large number of particles of 25 μm or larger are produced; these particles are sufficiently large to clog the majority of the pristine Super P carbon pores with a size between 25 and 50 μm. As a consequence, the larger particles produced at higher χ values result in less dramatic changes.

Figure 11

Figure 11. Number of clogged pores for the Super P electrode structure calculated using PNM modelling of the pristine Super P electrode structure obtained from tomographic imaging. The discharge current density is 100 μA g–1. Plots are shown for five escape factors (χ =0, 0.25, 0.5, 0.75, and 1).

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As was shown in a previous work, (40) PNM calculations on three-dimensional electrode structures also yield larger tortuosity factor changes on discharge compared to the Bruggeman relation. The larger increase in the tortuosity factor for PNM calculations is due to the incorporation of pore clogging effects in the simulations of 3D electrode structures. Similarly here, pore clogging could be the reason why a more dramatic tortuosity factor change is observed in PFG-NMR measurements compared to the Bruggeman relation.

kMC Modeling

Another factor that can affect the effective diffusion coefficient of a molecule in a porous media is the frequent collisions of particles with the pore wall. This phenomenon, which is called Knudsen diffusion, is particularly important when the pore is very small. This effect is naturally present in the effective diffusion coefficient measurements done with PFG-NMR experiments. Yet in most cases, the tortuosity factor is considered only as a function of porosity. Here, to quantify the effect of pore size on diffusion, a kMC model is used.
To assess the importance of this effect, the bulk diffusion coefficient was given as an input and set to 5·10–9 m2 s-1, which is within the typical range of oxygen diffusion coefficients reported for Li-O2 battery electrolytes. (22) Oxygen diffusion is studied first before changing the diffusing molecule to tetraglyme molecules. Nine different pore sizes were tested, corresponding to cylindrical pores with diameters of 1, 2, 3, 4, 5, 10, 25, 50, and 100 nm, which are within the range of Super P pore sizes. (8) The obtained MSD curves are shown in Figure 12 (and Figure S9 for x, y, and z contributions to the overall diffusion). The MSD values increase nonlinearly with time for short times but become linear after 1 μs. This is particularly visible for the 100 and 50 nm pore sizes.

Figure 12

Figure 12. MSD plots obtained from kMC calculations for several pore sizes.

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The diffusion coefficient as a function of the pore diameter calculated from kMC trajectories is shown in Figure 13. While the effective diffusion coefficient does not vary much for pores with diameters larger than 25 nm, a pore size effect is seen below 25 nm. The effective diffusion coefficient decreases sharply for pores with diameters below 4–5 nm.

Figure 13

Figure 13. O2 diffusion coefficients calculated using the kMC model for various pore diameters.

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The sensitivity of these trends on the input diffusion coefficient value and voxel size was analyzed. As the molecule tracked in the PFG-NMR experiments is tetraglyme, two similar kMC calculations were done with tetraglyme as the diffusing molecule instead of O2. For the first of these two additional kMC calculations, the input value for the bulk diffusion coefficient was simply changed from the value of O2 to the tetraglyme bulk diffusion coefficient (measured by PFG-NMR and equal to 3.42 10–10 m2 s–1). In the second calculation the voxel size was changed from 0.5 to 0.75 nm (to represent the longer chain of tetraglyme molecules). The diffusion coefficient value does not change the pore size effect on the effective diffusion coefficient values, while the voxel size seems to affect the effective diffusion coefficient values only slightly (Figure S10).
These three kMC calculations confirm that the pore size effect on the effective diffusion coefficient is not noticeable for pores larger than 5 nm and only significant below that size. These trends are consistent with PFG-NMR measurements conducted by Forse et al. (35) for self-diffusion coefficients of ions in activated carbons for supercapacitors. They measured effective diffusion coefficients about two orders of magnitude lower for ions in nanopores compared to the bulk values. These kMC calculations and prior reports on the pore size effect on the effective diffusion coefficient confirm our assumption that the change in the measured effective diffusion coefficient values are mainly influenced by pore clogging in the electrode mesostructure.

Summary and Conclusions

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In this study, several Super P electrodes were discharged to various depths of discharge and effective diffusion coefficients of tetraglyme molecules in the porous cathodes were measured using PFG-NMR experiments. This allowed for the extraction of the tortuosity factor evolution along discharge for Li-O2 batteries. It was shown that the tortuosity factor increases with the depth of discharge. The effect of the solvent on the tortuosity factor evolution of Super P electrodes was also studied. When a DME-based electrolyte is used, the tortuosity factor increases more dramatically than when tetraglyme is used as the electrolyte solvent. The tortuosity factor evolution along discharge is confirmed with tomographic imaging for cells discharged with tetraglyme electrolytes. This difference between solvents is attributed to the difference in the size of discharge products in the two electrolytes.
PNM and kMC calculations were used to investigate the relative importance of pore clogging and pore shrinking on the effective diffusion coefficients. PNM calculations showed that electrolytes with larger escape factor (higher donor number) lead to more pore clogging. This provides a plausible reason for why the tortuosity factor of the electrodes discharged in DME based electrolyte increases more than seen in tetraglyme. The kMC calculations show that there is indeed a pore size effect on diffusion, but it manifests itself only for very small pores with diameters below 5 nm. In Super P electrodes, less than 0.1% of the porous volume correspond to pores with radiuses below 90 nm, which makes this effect negligible in these electrodes. (12) In the future, these results could be integrated in the PNM model to improve its accuracy by including the pore size effect on diffusion; the PNM would capture in a better way the influence of the pore shrinkage along discharge.
These experimental and modeling results can be used to suggest ways of optimizing battery performance. For instance, using an electrolyte that promotes formation of large discharge products can provide high discharge capacities but may not perform well at high discharge rates as the pore clogging will hinder ionic transport. On the contrary, electrolytes in which small particles are favored reduce pore clogging and favor faster transport. Porous carbon materials and electrolytes thus have to be optimized in parallel to have particle sizes large enough for a high capacity but without clogging the electrode pores. The measured rate of change of tortuosity could in future work be used to optimize cell performance. For instance, there are several factors, such as high discharge current, that could lead to smaller Li2O2 particle sizes. The ability to measure the electrode tortuosity after the cells have been discharged allows one to optimize the discharge rate to maximize capacity while still maintaining a low tortuosity. Furthermore, it is potentially possible to determine whether shut-down of the cell is more likely due to a decrease in the overall tortuosity or to pore blockage on the air side of the electrode.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpcc.0c10417.

  • More details on PFG-NMR measurements, error analyses, calculating diffusion coefficients from kMC, and sensitivity analysis for kMC data are provided (PDF)

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
    • Clare P. Grey - Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.;  ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Orcidhttp://orcid.org/0000-0001-5572-192X;  Email: [email protected]
  • Authors
    • Amangeldi Torayev - Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.;  ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France
    • Simon Engelke - Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.;  Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, U.K.
    • Zeliang Su - Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Orcidhttp://orcid.org/0000-0001-7142-8977
    • Lauren E. Marbella - Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.;  Department of Chemical Engineering, Columbia University, 500 W 120th St, New York, New York 10027, United States;  Orcidhttp://orcid.org/0000-0003-1639-3913
    • Vincent De Andrade - X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont 60439, United States
    • Arnaud Demortière - Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Orcidhttp://orcid.org/0000-0002-4706-4592
    • Pieter C. M. M. Magusin - Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.;  ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Orcidhttp://orcid.org/0000-0003-1167-3764
    • Céline Merlet - ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  CIRIMAT, Université de Toulouse, CNRS, Bât. CIRIMAT, 118, route de Narbonne, Toulouse cedex 9 31062, France;  Orcidhttp://orcid.org/0000-0003-3758-273X
    • Alejandro A. Franco - Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS 7314, Université de Picardie Jules Verne, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  ALISTORE-European Research Institute, FR CNRS 3104, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, Hub de l’Energie, 15 Rue Baudelocque, Amiens 80039, France;  Institut Universitaire de France, 103 Boulevard Saint-Michel, Paris 75005, France;  Orcidhttp://orcid.org/0000-0001-7362-7849
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors acknowledge the ALISTORE European Research Institute for the funding support of A.T.’s Ph.D. thesis. S.E. acknowledges funding from the EPSRC grant EP/L016087/1. A.A.F. acknowledges the Institut Universitaire de France and the EIG CONCERT Japan (project Car Free) for funding support. This work has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme through the projects BATNMR, ARTISTIC and SuPERPORES (Grant nos. 835073, 772873, and 714581, respectively). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357.

References

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This article references 53 other publications.

  1. 1
    Abraham, K. M.; Jiang, Z. A Polymer Electrolyte-Based Rechargeable Lithium/Oxygen Battery. J. Electrochem. Soc. 1996, 143, 1– 5,  DOI: 10.1149/1.1836378
    [Crossref], [CAS], Google Scholar
    1
    A polymer electrolyte-based rechargeable lithium/oxygen battery
    Abraham, K. M.; Jiang, Z.
    Journal of the Electrochemical Society (1996), 143 (1), 1-5CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    A novel rechargeable Li/O battery is described. The battery comprises a Li+ conductive org. polymer electrolyte membrane sandwiched by a thin Li metal foil anode and a thin carbon composite electrode on which oxygen, the electroactive cathode material, accessed from the environment, is reduced during discharge to generate elec. power. It features an all solid state design in which electrode and electrolyte layers are laminated to form a 200-300 μm thick battery cell. The overall cell reaction during discharge appears to be 2Li + O2 → Li2O2. The battery has an open-circuit voltage of ∼3 V, and a load voltage that spans between 2 and 2.8 V depending on the load resistance. The cell can be recharged with good coulombic efficiency using a cobalt phthalocyanine catalyzed carbon electrode.
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  2. 2
    Ma, Z.; Yuan, X.; Li, L.; Ma, Z.-F.; Wilkinson, D. P.; Zhang, L.; Zhang, J. A Review of Cathode Materials and Structures for Rechargeable Lithium–Air Batteries. Energy Environ. Sci. 2015, 8, 2144– 2198,  DOI: 10.1039/C5EE00838G
    [Crossref], [CAS], Google Scholar
    2
    A review of cathode materials and structures for rechargeable lithium-air batteries
    Ma, Zhong; Yuan, Xianxia; Li, Lin; Ma, Zi-Feng; Wilkinson, David P.; Zhang, Lei; Zhang, Jiujun
    Energy & Environmental Science (2015), 8 (8), 2144-2198CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
    Rechargeable lithium air (Li-air) batteries, esp. the non-aq. type, are considered the most promising energy storage and conversion device candidates for use in future elec. vehicle applications due to their ultrahigh energy d. The air cathode has been identified as a key factor affecting the overall performance of Li-air batteries. The current low level performance of air cathodes is the major challenge hindering com. applications of Li-air batteries. In the past decade, a great many cathode materials, structures and fabrication processes have been developed and investigated with the goal of enhancing cathode performance. This paper reviews, the role of the cathode in non-aq. Li-air batteries including the cathode reaction mechanisms and the properties and morphologies of cathode materials, followed by approaches to optimize cathode performance. The most recently published global progress and the main achievements in the field of Li-air batteries are also systematically and critically reviewed in terms of cathode materials, structures and fabrication processes, with the objective of providing some state-of-the-art information. Tech. challenges are analyzed, and insights into future research directions for overcoming these development challenges of rechargeable non-aq. Li-air battery cathodes are also identified in this review paper.
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  3. 3
    Viswanathan, V.; Thygesen, K. S.; Hummelshøj, J. S.; Nørskov, J. K.; Girishkumar, G.; McCloskey, B. D.; Luntz, A. C. Electrical Conductivity in Li2O2 and Its Role in Determining Capacity Limitations in Non-Aqueous Li-O2 Batteries. J. Chem. Phys. 2011, 135, 214704,  DOI: 10.1063/1.3663385
    [Crossref], [PubMed], [CAS], Google Scholar
    3
    Electrical conductivity in Li2O2 and its role in determining capacity limitations in non-aqueous Li-O2 batteries
    Viswanathan, V.; Thygesen, K. S.; Hummelshoj, J. S.; Norskov, J. K.; Girishkumar, G.; McCloskey, B. D.; Luntz, A. C.
    Journal of Chemical Physics (2011), 135 (21), 214704/1-214704/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Nonaq. Li-air or Li-O2 cells show considerable promise as a very high energy d. battery couple. Such cells, however, show sudden death at capacities far below their theor. capacity and this, among other problems, limits their practicality. This sudden death arises from limited charge transport through the growing Li2O2 film to the Li2O2-electrolyte interface, and this limitation defines a crit. film thickness, above which it is not possible to support electrochem. at the Li2O2-electrolyte interface. The authors report both electrochem. expts. using a reversible internal redox couple and a 1st principles metal-insulator-metal charge transport model to probe the elec. cond. through Li2O2 films produced during Li-O2 discharge. Both expt. and theory show a sudden death in charge transport when film thickness is ∼5 to 10 nm. The theor. model shows that this occurs when the tunneling current through the film can no longer support the electrochem. current. Thus, engineering charge transport through Li2O2 is a serious challenge if Li-O2 batteries are ever to reach their potential. (c) 2011 American Institute of Physics.
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  4. 4
    Yin, Y.; Torayev, A.; Gaya, C.; Mammeri, Y.; Franco, A. A. Linking the Performances of Li–O2 Batteries to Discharge Rate and Electrode and Electrolyte Properties through the Nucleation Mechanism of Li2O2. J. Phys. Chem. C 2017, 121, 19577– 19585,  DOI: 10.1021/acs.jpcc.7b05224
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    4
    Linking the Performances of Li-O2 Batteries to Discharge Rate and Electrode and Electrolyte Properties through the Nucleation Mechanism of Li2O2
    Yin, Yinghui; Torayev, Amangeldi; Gaya, Caroline; Mammeri, Youcef; Franco, Alejandro A.
    Journal of Physical Chemistry C (2017), 121 (36), 19577-19585CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Li-O2 batteries have attracted a lot of attention because of their high theor. capacity. Due to the high complexity of these systems, deep understanding of the discharge mechanism is still needed to push the state-of-the-art performance of Li-O2 batteries to the theor. one. A universal multiscale model combining nucleation theory, detailed reaction kinetics, and mass transport is presented in this article, which encompasses the impacts of discharge rate, electrolyte property and electrode surface properties on the discharge capacity of Li-O2 batteries and on the morphol. of the Li2O2 arising from its nucleation process.
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  5. 5
    Luntz, A. C.; Viswanathan, V.; Voss, J.; Varley, J. B.; Nørskov, J. K.; Scheffler, R.; Speidel, A. Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries. J. Phys. Chem. Lett. 2013, 4, 3494– 3499,  DOI: 10.1021/jz401926f
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    5
    Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries
    Luntz, A. C.; Viswanathan, V.; Voss, J.; Varley, J. B.; Noerskov, J. K.; Scheffler, R.; Speidel, A.
    Journal of Physical Chemistry Letters (2013), 4 (20), 3494-3499CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The authors describe Li-O2 discharge expts. in a bulk electrolysis cell as a function of c.d. and temp. In combination with a simple model, these imply that charge transport through Li2O2 in Li-O2 batteries at practical current densities is based principally on hole tunneling, with hole polaron cond. playing a significant role near the end of low current discharges and at temps. >30°. Also charge-transport limitations are less significant during charging than those in discharge. A key element of the model that qual. explains all results is the alignment of the Li2O2 valence band max. close to the electrochem. Fermi energy and how this alignment varies with overpotentials during discharge and charge. In fact, comparison of the model with the expts. allows detn. of the alignment of the bands relative to the electrochem. Fermi level.
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  6. 6
    Mitchell, R. R.; Gallant, B. M.; Shao-Horn, Y.; Thompson, C. V. Mechanisms of Morphological Evolution of Li2O2 Particles during Electrochemical Growth. J. Phys. Chem. Lett. 2013, 4, 1060– 1064,  DOI: 10.1021/jz4003586
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    6
    Mechanisms of Morphological Evolution of Li2O2 Particles during Electrochemical Growth
    Mitchell, Robert R.; Gallant, Betar M.; Shao-Horn, Yang; Thompson, Carl V.
    Journal of Physical Chemistry Letters (2013), 4 (7), 1060-1064CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Li-O2 batteries, wherein solid Li2O2 is formed at the porous air cathode during discharge, are candidates for high gravimetric energy (3212 W-h/kgLi2O2 ) storage for elec. vehicles. Understanding and controlling the nucleation and morphol. evolution of Li2O2 particles upon discharge is key to achieving high volumetric energy densities. SEM and TEM were used to characterize the discharge product formed in Li-O2 batteries on electrodes composed of carpets of aligned C nanotubes. At low discharge rates, Li2O2 particles form 1st as stacked thin plates, ∼10 nm in thickness, which spontaneously splay so that secondary nucleation of new plates eventually leads to the development of a particle with a toroidal shape. Li2O2 crystallites have large (001) crystal faces consistent with the theor. Wulff shape and appear to grow by a layer-by-layer mechanism. But at high discharge rates, copious nucleation of equiaxed Li2O2 particles precedes growth of disks and toroids.
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  7. 7
    Zhai, D.; Wang, H.-H.; Yang, J.; Lau, K. C.; Li, K.; Amine, K.; Curtiss, L. A. Disproportionation in Li-O2 Batteries Based on a Large Surface Area Carbon Cathode. J. Am. Chem. Soc. 2013, 135, 15364– 15372,  DOI: 10.1021/ja403199d
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    7
    Disproportionation in Li-O2 batteries based on a large surface area carbon cathode
    Zhai, Dengyun; Wang, Hsien-Hau; Yang, Junbing; Lau, Kah Chun; Li, Kaixi; Amine, Khalil; Curtiss, Larry A.
    Journal of the American Chemical Society (2013), 135 (41), 15364-15372CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    In this paper we report on a kinetics study of the discharge process and its relationship to the charge overpotential in a Li-O2 cell for large surface area cathode material. The kinetics study reveals evidence for a first-order disproportionation reaction during discharge from an oxygen-rich Li2O2 component with superoxide-like character to a Li2O2 component. The oxygen-rich superoxide-like component has a much smaller potential during charge (3.2-3.5 V) than the Li2O2 component (∼4.2 V). The formation of the superoxide-like component is likely due to the porosity of the activated carbon used in the Li-O2 cell cathode that provides a good environment for growth during discharge. The discharge product contg. these two components is characterized by toroids, which are assemblies of nanoparticles. The morphol. growth and decompn. process of the toroids during the reversible discharge/charge process was obsd. by SEM and is consistent with the presence of the two components in the discharge product. The results of this study provide new insight into how growth conditions control the nature of discharge product, which can be used to achieve improved performance in Li-O2 cell.
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  8. 8
    Xue, K.-H.; McTurk, E.; Johnson, L.; Bruce, P. G.; Franco, A. A. A Comprehensive Model for Non-Aqueous Lithium Air Batteries Involving Different Reaction Mechanisms. J. Electrochem. Soc. 2015, 162, A614– A621,  DOI: 10.1149/2.0121504jes
    [Crossref], [CAS], Google Scholar
    8
    A Comprehensive Model for Non-Aqueous Lithium Air Batteries Involving Different Reaction Mechanisms
    Xue, Kan-Hao; McTurk, Euan; Johnson, Lee; Bruce, Peter G.; Franco, Alejandro A.
    Journal of the Electrochemical Society (2015), 162 (4), A614-A621CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    There are various reaction mechanisms in the discharge process of a nonaq. lithium-air battery. Recently, it has been identified that low current rate and high donor no. solvents can lead to soln. phase reaction, but high current rate and low donor no. solvents will cause thin film growth covering the active cathode surface. In this paper we extend our previous lithium-air battery multiscale model, which considers the thin film growth mode, to the general case where both surface thin film growth and soln. phase reaction coexist. A detailed mechanism is proposed and simulation results are compared with exptl. data.
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  9. 9
    Laoire, C. O.; Mukerjee, S.; Abraham, K. M.; Plichta, E. J.; Hendrickson, M. A. Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications. J. Phys. Chem. C 2009, 113, 20127– 20134,  DOI: 10.1021/jp908090s
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    9
    Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications
    Laoire, Cormac O.; Mukerjee, Sanjeev; Abraham, K. M.; Plichta, Edward J.; Hendrickson, Mary A.
    Journal of Physical Chemistry C (2009), 113 (46), 20127-20134CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The capabilities of a Li anode in a Li battery has until now been limited by the low capacity intercalation and conversion reactions at the cathodes. It is however possible to remove these electrodes and allow Li to react directly with O in the atm., forming a Li-air battery. The Li/O2 battery redox couple has a theor. sp. energy of 5200 W-h/kg and represents the ultimate, environmentally friendly electrochem. power source. The role of electrolyte, in particular the role of ion-conducting salts, in detg. the reversibility and kinetics of O redn. in nonaq. electrolytes was studied. Understanding of this high energy d. battery is crucial to harnessing its full energy potential. The kinetics and mechanisms of O2 redn. in solns. of hexafluorophosphate A+PF6-, where A = Bu4N (TBA), K, Na, and Li, in MeCN are reported on glassy C electrodes using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The cations in the electrolyte influence the redn. mechanism of O2. Larger cations represented by TBA salts displayed reversible O2/O2- redox couple, in contrast to those contg. the smaller Li (and other alkali metal) cations, where an irreversible 1-electron redn. of O2 to LiO2, and other alkali metal superoxides, occurs as the 1st process. It was also found that the LiO2 formed initially decomps. to Li2O2. Electrochem. data support the view that alkali metal oxides formed via electrochem. and chem. reactions passivate the electrode surface, making the processes irreversible. The O2 redn. mechanisms in the presence of the different cations have been supplemented by kinetic parameters detd. from detailed analyses of the CV and RDE data. The Lewis acid characteristics of the cation appear to be crucial in detg. the reversibility of the system. These results can contribute to the development of the Li-air battery.
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  10. 10
    Albertus, P.; Girishkumar, G.; McCloskey, B.; Sánchez-Carrera, R. S.; Kozinsky, B.; Christensen, J.; Luntz, A. C. Identifying Capacity Limitations in the Li/Oxygen Battery Using Experiments and Modeling. J. Electrochem. Soc. 2011, 158, A343– A351,  DOI: 10.1149/1.3527055
    [Crossref], [CAS], Google Scholar
    10
    Identifying Capacity Limitations in the Li/Oxygen Battery Using Experiments and Modeling
    Albertus, Paul; Girishkumar, G.; McCloskey, Bryan; Sanchez-Carrera, Roel S.; Kozinsky, Boris; Christensen, Jake; Luntz, A. C.
    Journal of the Electrochemical Society (2011), 158 (3), A343-A351CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    The Li/oxygen battery may achieve a high practical specific energy as its theor. specific energy is 11,400 Wh/kg Li assuming Li2O2 is the product. To help understand the physics of the Li/oxygen battery the first physics-based model that incorporates the major thermodn., transport, and kinetic processes is presented. A good match between porous-electrode expts. and simulations is obtained by using an empirical fit to the resistance of the discharge products (which include carbonates and oxides when using carbonate solvents) as a function of thickness that is obtained from flat-electrode expts. The expts. and model indicate that the discharge products are electronically resistive, limiting their thickness to tens of nanometers and their vol. fraction in one of the discharged porous electrodes to a few percent. Flat-electrode expts., where pore clogging is impossible, show passivation similar to porous-electrode expts. and allow to conclude that elec. passivation is the dominant capacity-limiting mechanism in the cells. Although in carbonate solvents Li2O2 is not the dominant discharge product, it is argued that the implications of this model, (i.e., elec. passivation by the discharge products limits the capacity) also apply if Li2O2 is the discharge product, as it is an intrinsic electronic insulator.
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  11. 11
    Franco, A. A.; Xue, K.-H. Carbon-Based Electrodes for Lithium Air Batteries: Scientific and Technological Challenges from a Modeling Perspective. ECS J. Solid State Sci. Technol. 2013, 2, M3084– M3100,  DOI: 10.1149/2.012310jss
    [Crossref], [CAS], Google Scholar
    11
    Carbon-based electrodes for lithium air batteries: scientific and technological challenges from a modeling perspective
    Franco, Alejandro A.; Xue, Kan-Hao
    ECS Journal of Solid State Science and Technology (2013), 2 (10), M3084-M3100CODEN: EJSSBG; ISSN:2162-8769. (Electrochemical Society)
    A review. The carbon-based pos. electrode of Lithium Air Batteries (LABs) is the component where the major competitive mechanisms occur, such as the electrochem. reactions leading to the formation and decompn. of multiple types of lithium oxides, lithium ion and electronic transport as well as oxygen transport. Through a multiscale viewpoint, this review discusses available models describing LAB carbon-based electrodes from the atomistic to continuum approaches. Relevance of those approaches vs. exptl. data as well as the remaining scientific and technol. challenges of these technologies are analyzed. Finally, this review briefly introduces a new theory aiming at studying the impact of the pos. electrode carbon structure onto the cyclability of LABs.
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  12. 12
    Xue, K.-H.; Nguyen, T.-K.; Franco, A. A. Impact of the Cathode Microstructure on the Discharge Performance of Lithium Air Batteries: A Multiscale Model. J. Electrochem. Soc. 2014, 161, E3028– E3035,  DOI: 10.1149/2.002408jes
    [Crossref], [CAS], Google Scholar
    12
    Impact of the Cathode Microstructure on the Discharge Performance of Lithium Air Batteries: A Multiscale Model
    Xue, Kan-Hao; Nguyen, Trong-Khoa; Franco, Alejandro A.
    Journal of the Electrochemical Society (2014), 161 (8), E3028-E3035CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    A multiscale model of lithium air batteries considering cathode pore size distribution is proposed, where the morphol. of the discharge product, Li2O2, is assumed to be thin films covering the surface of the pores. In the model, active surface area degrades during discharge because of three reasons. First, the effective radius of pores decreases due to Li2O2 coverage. Secondly, small pores may be fully choked. Thirdly, thick Li2O2 film may block the electron tunneling process, rendering the surface inactive. Simulation results reveal that the end of discharge in cells made of Super P and Ketjen Black carbons is caused by unavailable surface area near the air inlet, rather than the full choking of pores. Larger discharge capacity is found in the Ketjen Black cell because its high sp. surface area leads to slower Li2O2 thickness growth rate. This tunneling-limited model is compared with a linear resistance model where the Li2O2 thin film resistance is assumed to be proportional to its thickness. Different shapes of discharge curves were discovered: the former has a long discharge plateau followed by a sudden drop of cell voltage, while the latter shows a gradual decrease of cell voltage. These results are discussed in relation to the exptl. knowledge.
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  13. 13
    Liu, J.; Rahimian, S. K.; Monroe, C. W. Capacity-Limiting Mechanisms in Li/O2 Batteries. Phys. Chem. Chem. Phys. 2016, 18, 22840– 22851,  DOI: 10.1039/C6CP04055A
    [Crossref], [PubMed], [CAS], Google Scholar
    13
    Capacity-limiting mechanisms in Li/O2 batteries
    Liu, Jing; Khaleghi Rahimian, Saeed; Monroe, Charles W.
    Physical Chemistry Chemical Physics (2016), 18 (33), 22840-22851CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A continuum model of an aprotic lithium/oxygen battery is validated against exptl. first-discharge data and used to examine how the apparent cell capacity is affected by macroscopic multicomponent mass transfer, interfacial kinetics, and electronic conduction or tunneling through the discharge product. The model accounts for the three-phase nature of the pos. electrode in detail, including an explicit discharge-product layer whose properties and vol. distribution generally depend on the local discharge depth. Several hypothetical pos.-electrode reaction mechanisms involving different product morphologies and electron-transfer sites are explored within the theor. framework. To match exptl. discharge-voltage vs. capacity and capacity vs. discharge-current trends qual., the discharge-product layer must be assumed to have electronic resistivity several orders of magnitude lower than typical insulators, supporting the notion that the presence of lithium peroxide does not wholly prevent electrons from reaching dissolved reactants. The discharge product also appears to allow charge transport over length scales longer than electron tunneling permits. sudden death of voltage in lithium/oxygen cells is explained by macroscopic oxygen-diffusion limitations in the pos. electrode at high rates, and by pore clogging assocd. with discharge-product formation at low rates.
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  14. 14
    Bardenhagen, I.; Yezerska, O.; Augustin, M.; Fenske, D.; Wittstock, A.; Bäumer, M. In Situ Investigation of Pore Clogging during Discharge of a Li/O2 Battery by Electrochemical Impedance Spectroscopy. J. Power Sources 2015, 278, 255– 264,  DOI: 10.1016/j.jpowsour.2014.12.076
    [Crossref], [CAS], Google Scholar
    14
    In situ investigation of pore clogging during discharge of a Li/O2 battery by electrochemical impedance spectroscopy
    Bardenhagen, Ingo; Yezerska, Olga; Augustin, Matthias; Fenske, Daniela; Wittstock, Arne; Baeumer, Marcus
    Journal of Power Sources (2015), 278 (), 255-264CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    The behavior of three gas diffusion electrodes (GDE) with macro- and mesopores is investigated by in situ electrochem. impedance spectroscopy (EIS) in the Li/O2 battery system while discharging. Using a three electrode setup the current response from the anode (Li metal) and cathode (GDE) can be sepd. and the changes of the electrochem. processes at the GDE during discharge can be obsd., exclusively. Up to four processes are identified with different time consts. which is assigned to the lithium ion migration through a surface layer, the charge-transfer from the carbon surface to the mol. oxygen, the lithium ion and oxygen diffusion towards the cathode surface and, in case of the mesoporous materials, the lithium ion movement inside the pores, along the pore axis. The latter finding reflects that pore clogging of such is a limiting factor for the discharge of the Li/O2 battery. A large mesopore vol. as in the xerogel electrode, however, allows for a high storage capability and a long and const. oxygen redn. It is demonstrated that the three electrode EIS proves to be a powerful in situ diagnostic tool to det. the state and, hence, the reversibility of the reactions at the cathode.
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  15. 15
    Aklalouch, M.; Olivares-Marín, M.; Lee, R. C.; Palomino, P.; Enciso, E.; Tonti, D. Mass-Transport Control on the Discharge Mechanism in Li-O2 Batteries Using Carbon Cathodes with Varied Porosity. ChemSusChem 2015, 8, 3465– 3471,  DOI: 10.1002/cssc.201500719
    [Crossref], [PubMed], [CAS], Google Scholar
    15
    Mass-transport Control on the Discharge Mechanism in Li-O2 Batteries Using Carbon Cathodes with Varied Porosity
    Aklalouch, Mohamed; Olivares-Marin, Mara; Lee, Rung-Chuan; Palomino, Pablo; Enciso, Eduardo; Tonti, Dino
    ChemSusChem (2015), 8 (20), 3465-3471CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
    By comparing carbon electrodes with varying porosity in Li-O2 cells, we show that the effect of electrolyte stirring at a given c.d. can result in a change from 2D to 3D growth of discharged deposits. The change of morphol. is evident using electron microscopy and by analyzing electrode pore size distribution with respect to discharge capacity. As a consequence, carbon electrodes with different textural properties exhibit different capacity enhancements in stirred-electrolyte cells. We demonstrate that mass transport can directly control the discharge mechanism, similar to the electrolyte compn. and c.d., which have already been recognized as detg. factors.
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  16. 16
    Ding, N.; Chien, S. W.; Hor, T. S. A.; Lum, R.; Zong, Y.; Liu, Z. Influence of Carbon Pore Size on the Discharge Capacity of Li-O2 Batteries. J. Mater. Chem. A 2014, 2, 12433– 12441,  DOI: 10.1039/C4TA01745E
    [Crossref], [CAS], Google Scholar
    16
    Influence of carbon pore size on the discharge capacity of Li-O2 batteries
    Ding, Ning; Chien, Sheau Wei; Hor, T. S. Andy; Lum, Regina; Zong, Yun; Liu, Zhaolin
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (31), 12433-12441CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Porous carbon materials play key roles in rechargeable Li-O2 batteries as oxygen diffusion media and sites for reversible electrode reactions. Despite tremendous efforts in the synthesis of various porous carbon materials, the effect of carbon materials on cell capacity remains unclear. Based on the study of eight different carbon electrode materials with various pore sizes and pore vols. in Li-O2 batteries, it was found that the initial discharge capacity was hardly affected by the surface area or pore vol. Instead, it was directly correlated with the pore sizes. To further verify this finding, meso- and macro-porous carbon materials with pore sizes in the range of 20-100 nm were prepd. using spherical silica as a template. The results clearly showed that the cell capacity increases with the increase of pore size and eventually reached its max. at 7169 mA h g-1 at a pore size of 80 nm. A phys. model proposed to illustrate the effect of carbon pore size on cell capacity is the formation of a monolayer of Li2O2 with a thickness of 7.8 nm inside the carbon pores during the discharge process which limits the diffusion of incoming oxygen at smaller pore size (< 80 nm).
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  17. 17
    Kim, D. Y.; Kim, M.; Kim, D. W.; Suk, J.; Park, J. J.; Park, O. O.; Kang, Y. Graphene Paper with Controlled Pore Structure for High-Performance Cathodes in Li–O2 Batteries. Carbon N. Y. 2016, 100, 265– 272,  DOI: 10.1016/j.carbon.2016.01.013
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Lin, Y.; Moitoso, B.; Martinez-Martinez, C.; Walsh, E. D.; Lacey, S. D.; Kim, J. W.; Dai, L.; Hu, L.; Connell, J. W. Ultrahigh-Capacity Lithium-Oxygen Batteries Enabled by Dry-Pressed Holey Graphene Air Cathodes. Nano Lett. 2017, 17, 3252– 3260,  DOI: 10.1021/acs.nanolett.7b00872
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    18
    Ultrahigh-Capacity Lithium-Oxygen Batteries Enabled by Dry-Pressed Holey Graphene Air Cathodes
    Lin, Yi; Moitoso, Brandon; Martinez-Martinez, Chalynette; Walsh, Evan D.; Lacey, Steven D.; Kim, Jae-Woo; Dai, Liming; Hu, Liangbing; Connell, John W.
    Nano Letters (2017), 17 (5), 3252-3260CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    Lithium-oxygen (Li-O2) batteries have the highest theor. energy d. of all the Li-based energy storage systems, but many challenges prevent them from practical use. A major obstacle is the sluggish performance of the air cathode, where both oxygen redn. (discharge) and oxygen evolution (charge) reactions occur. Recently, there have been significant advances in the development of graphene-based air cathode materials with a large surface area and catalytically active for both oxygen redn. and evolution reactions, esp. with addnl. catalysts or dopants. However, most studies reported so far have examd. air cathodes with a limited areal mass loading rarely exceeding 1 mg/cm2. Despite the high gravimetric capacity values achieved, the actual (areal) capacities of those batteries were far from sufficient for practical applications. Here, we present the fabrication, performance, and mechanistic investigations of high-mass-loading (up to 10 mg/cm2) graphene-based air electrodes for high-performance Li-O2 batteries. Such air electrodes could be easily prepd. within minutes under solvent-free and binder-free conditions by compression-molding holey graphene materials because of their unique dry compressibility assocd. with in-plane holes on the graphene sheet. Li-O2 batteries with high air cathode mass loadings thus prepd. exhibited excellent gravimetric capacity as well as ultrahigh areal capacity (as high as ∼40 mAh/cm2). The batteries were also cycled at a high curtailing areal capacity (2 mAh/cm2) and showed a better cycling stability for ultrathick cathodes than their thinner counterparts. Detailed post-mortem analyses of the electrodes clearly revealed the battery failure mechanisms under both primary and secondary modes, arising from the oxygen diffusion blockage and the catalytic site deactivation, resp. These results strongly suggest that the dry-pressed holey graphene electrodes are a highly viable architectural platform for high-capacity, high-performance air cathodes in Li-O2 batteries of practical significance.
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  19. 19
    Yu, R.; Fan, W.; Guo, X.; Dong, S. Highly Ordered and Ultra-Long Carbon Nanotube Arrays as Air Cathodes for High-Energy-Efficiency Li-Oxygen Batteries. J. Power Sources 2016, 306, 402– 407,  DOI: 10.1016/j.jpowsour.2015.12.042
    [Crossref], [CAS], Google Scholar
    19
    Highly ordered and ultra-long carbon nanotube arrays as air cathodes for high-energy-efficiency Li-oxygen batteries
    Yu, Ruimin; Fan, Wugang; Guo, Xiangxin; Dong, Shaoming
    Journal of Power Sources (2016), 306 (), 402-407CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Carbonaceous air cathodes with rational architecture are vital for the nonaq. Li-O2 batteries to achieve large energy d., high energy efficiency and long cycle life. In this work, we report the cathodes made of highly ordered and vertically aligned carbon nanotubes grown on permeable Ta foil substrates (VACNTs-Ta) via thermal chem. vapor deposition. The VACNTs-Ta, composed of uniform carbon nanotubes with approx. 240 μm in superficial height, has the super large surface area. Meanwhile, the oriented carbon nanotubes provide extremely outstanding passageways for Li ions and oxygen species. Electrochem. tests of VACNTs-Ta air cathodes show enhancement in discharge capacity and cycle life compared to those made from short-range oriented and disordered carbon nanotubes. By further combining with the LiI redox mediator that is dissolved in the tetraethylene di-Me glycol based electrolytes, the batteries exhibit more than 200 cycles at the c.d. of 200 mA g-1 with a cut-off discharge capacity of 1000 mA h g-1, and their energy efficiencies increase from 50% to 82%. The results here demonstrate the importance of cathode construction for high-energy-efficiency and long-life Li-O2 batteries.
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  20. 20
    Aurbach, D.; McCloskey, B. D.; Nazar, L. F.; Bruce, P. G. Advances in Understanding Mechanisms Underpinning Lithium–Air Batteries. Nat. Energy 2016, 1, 16128,  DOI: 10.1038/nenergy.2016.128
    [Crossref], [CAS], Google Scholar
    20
    Advances in understanding mechanisms underpinning lithium-air batteries
    Aurbach, Doron; McCloskey, Bryan D.; Nazar, Linda F.; Bruce, Peter G.
    Nature Energy (2016), 1 (9), 16128CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
    A review. The rechargeable lithium-air battery has the highest theor. specific energy of any rechargeable battery and could transform energy storage if a practical device could be realized. At the fundamental level, little was known about the reactions and processes that take place in the battery, representing a significant barrier to progress. Here, we review recent advances in understanding the chem. and electrochem. that govern the operation of the lithium-air battery, esp. the reactions at the cathode. The mechanisms of O2 redn. to Li2O2 on discharge and the reverse process on charge are discussed in detail, as are their consequences for the rate and capacity of the battery. The various parasitic reactions involving the cathode and electrolyte during discharge and charge are also considered. We also provide views on understanding the stability of the cathode and electrolyte and examine design principles for better lithium-air batteries.
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  21. 21
    Abraham, K. M. Electrolyte-Directed Reactions of the Oxygen Electrode in Lithium-Air Batteries. J. Electrochem. Soc. 2014, 162, A3021– A3031,  DOI: 10.1149/2.0041502jes
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Laoire, C. O.; Mukerjee, S.; Abraham, K. M.; Plichta, E. J.; Hendrickson, M. A. Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium–Air Battery. J. Phys. Chem. C 2010, 114, 9178– 9186,  DOI: 10.1021/jp102019y
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    22
    Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium-Air Battery
    Laoire, Cormac O.; Mukerjee, Sanjeev; Abraham, K. M.; Plichta, Edward J.; Hendrickson, Mary A.
    Journal of Physical Chemistry C (2010), 114 (19), 9178-9186CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The influence of solvents on the O redn. reaction (ORR) in nonaq. electrolytes was studied for the mechanism of O electrode processes in a rechargeable Li-air battery. Using either Bu4NPF6 (TBAPF6) or LiPF6 electrolyte solns. in 4 different solvents, DMSO, MeCN, dimethoxyethane (DME), and tetraethylene glycol di-Me ether (TEGDME), possessing a range of donor nos. (DN), the solvent and the supporting electrolyte cations in the soln. act in concert to influence the nature of redn. products and their rechargeability. In solns. contg. TBA+, O2 redn. is a reversible 1-electron process involving the O2/O2- couple. However, in Li+-contg. electrolytes relevant to the Li-air battery, O2 redn. proceeds in a stepwise fashion to form O2-, O22-, and O2- as products. These reactions in the presence of Li+ are irreversible or quasi-reversible electrochem. processes, and the solvents have significant influence on the kinetics, and reversibility or lack thereof, of the different redn. products. The stabilization of the 1-electron redn. product, superoxide (O2-) in TBA+ solns. in all of the solvents examd. can be explained using Pearson's hard/soft acid base (HSAB) theory involving the formation of the TBA+---O2- complex. The HSAB theory coupled with the relative stabilities of the Li+-(solvent)n complexes existing in the different solvents also provide an explanation for the different O2 redn. products formed in Li+-conducting electrolyte solns. Reversible redn. of O2 to long-lived superoxide in a Li+-conducting electrolyte in DMSO was shown for the 1st time here. The results aid the selection of org. electrolyte solns. for use in rechargeable Li-air batteries.
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  23. 23
    Johnson, L.; Li, C.; Liu, Z.; Chen, Y.; Freunberger, S. A.; Ashok, P. C.; Praveen, B. B.; Dholakia, K.; Tarascon, J. M.; Bruce, P. G. The Role of LiO2 Solubility in O2 Reduction in Aprotic Solvents and Its Consequences for Li–O2 Batteries. Nat. Chem. 2014, 6, 1091– 1099,  DOI: 10.1038/nchem.2101
    [Crossref], [PubMed], [CAS], Google Scholar
    23
    The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li-O2 batteries
    Johnson, Lee; Li, Chunmei; Liu, Zheng; Chen, Yuhui; Freunberger, Stefan A.; Ashok, Praveen C.; Praveen, Bavishna B.; Dholakia, Kishan; Tarascon, Jean-Marie; Bruce, Peter G.
    Nature Chemistry (2014), 6 (12), 1091-1099CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    When lithium-oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 redn. in aprotic solvents is therefore essential to realizing their technol. potential. Two different models have been proposed for Li2O2 formation, involving either soln. or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 redn. across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 redn. through its effect on the soly. of LiO2, or, more precisely, the free energy of the reaction LiO2* .dblharw. Li(sol)+ + O2-(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-no. solvents are likely to lead to premature cell death, and that the future direction of research for lithium-oxygen batteries should focus on the search for new, stable, high-donor-no. electrolytes, because they can support higher capacities and can better sustain discharge.
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  24. 24
    Burke, C. M.; Pande, V.; Khetan, A.; Viswanathan, V.; Mccloskey, B. D. Enhancing Electrochemical Intermediate Solvation through Electrolyte Anion Selection to Increase Nonaqueous Li–O2 Battery Capacity. Proc. Natl. Acad., Sci. U. S. A. 2015, 112, 9293,  DOI: 10.1073/pnas.1505728112
    [Crossref], [PubMed], [CAS], Google Scholar
    24
    Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O2 battery capacity
    Burke, Colin M.; Pande, Vikram; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D.
    Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (30), 9293-9298CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Among the beyond Li-ion battery chemistries, nonaq. Li-O2 batteries have the highest theor. specific energy and, as a result, have attracted significant research attention over the past decade. A crit. scientific challenge facing nonaq. Li-O2 batteries is the electronically insulating nature of the primary discharge product, Li peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance soly. to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochem. stability of the system, thereby deleteriously affecting battery rechargeability. The authors report that a significant enhancement (greater than 4-fold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte soln. Using 7Li NMR and modeling, this improvement is a result of enhanced Li+ stability in soln., which, in turn, induces soly. of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate soly. and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. The authors believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochem. systems (e.g., Li-S batteries) where improving intermediate stability in soln. could induce desired mechanisms of product formation.
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  25. 25
    Aetukuri, N. B.; McCloskey, B. D.; García, J. M.; Krupp, L. E.; Viswanathan, V.; Luntz, A. C. Solvating Additives Drive Solution-Mediated Electrochemistry and Enhance Toroid Growth in Non-Aqueous Li-O2 Batteries. Nat. Chem. 2015, 7, 50– 56,  DOI: 10.1038/nchem.2132
    [Crossref], [PubMed], [CAS], Google Scholar
    25
    Solvating additives drive solution-mediated electrochemistry and enhance toroid growth in non-aqueous Li-O2 batteries
    Aetukuri, Nagaphani B.; McCloskey, Bryan D.; Garcia, Jeannette M.; Krupp, Leslie E.; Viswanathan, Venkatasubramanian; Luntz, Alan C.
    Nature Chemistry (2015), 7 (1), 50-56CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    Given their high theor. specific energy, Li-O batteries have received enormous attention as possible alternatives to current state-of-the-art rechargeable Li-ion batteries. However, the max. discharge capacity in nonaq. Li-O batteries is limited to a small fraction of its theor. value due to the build-up of insulating Li peroxide (Li2O2), the battery's primary discharge product. The discharge capacity can be increased if Li2O2 forms as large toroidal particles rather than as a thin conformal layer. Here, trace amts. of electrolyte additives, such as H2O, enhance the formation of Li2O2 toroids and result in significant improvements in capacity. The exptl. observations and a growth model show that the solvating properties of the additives prompt a soln.-based mechanism that is responsible for the growth of Li2O2 toroids. The authors present a general formalism describing an additive's tendency to trigger the soln. process, providing a rational design route for electrolytes that afford larger Li-O battery capacities.
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  26. 26
    Liu, T.; Frith, J. T.; Kim, G.; Kerber, R. N.; Dubouis, N.; Shao, Y.; Liu, Z.; Magusin, P. C. M. M.; Casford, M. T. L.; Garcia-Araez, N. The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries. J. Am. Chem. Soc. 2018, 140, 1428– 1437,  DOI: 10.1021/jacs.7b11007
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    26
    The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries
    Liu, Tao; Frith, James T.; Kim, Gunwoo; Kerber, Rachel N.; Dubouis, Nicolas; Shao, Yuanlong; Liu, Zigeng; Magusin, Pieter C. M. M.; Casford, Michael T. L.; Garcia-Araez, Nuria; Grey, Clare P.
    Journal of the American Chemical Society (2018), 140 (4), 1428-1437CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The parasitic reactions assocd. with reduced oxygen species and the difficulty in achieving the high theor. capacity have been major issues plaguing development of practical nonaq. Li-O2 batteries. We hereby address the above issues by exploring the synergistic effect of 2,5-di-tert-butyl-1,4-benzoquinone and H2O on the oxygen chem. in a nonaq. Li-O2 battery. Water stabilizes the quinone monoanion and dianion, shifting the redn. potentials of the quinone and monoanion to more pos. values (vs Li/Li+). When water and the quinone are used together in a (largely) nonaq. Li-O2 battery, the cell discharge operates via a two-electron oxygen redn. reaction to form Li2O2, with the battery discharge voltage, rate, and capacity all being considerably increased and fewer side reactions being detected. Li2O2 crystals can grow up to 30 μm, more than an order of magnitude larger than cases with the quinone alone or without any additives, suggesting that water is essential to promoting a soln. dominated process with the quinone on discharging. The catalytic redn. of O2 by the quinone monoanion is predominantly responsible for the attractive features mentioned above. Water stabilizes the quinone monoanion via hydrogen-bond formation and by coordination of the Li+ ions, and it also helps increase the solvation, concn., lifetime, and diffusion length of reduced oxygen species that dictate the discharge voltage, rate, and capacity of the battery. When a redox mediator is also used to aid the charging process, a high-power, high energy d., rechargeable Li-O2 battery is obtained.
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  27. 27
    Lacey, M. J.; Frith, J. T.; Owen, J. R. A Redox Shuttle to Facilitate Oxygen Reduction in the Lithium Air Battery. Electrochem. Commun. 2013, 26, 74– 76,  DOI: 10.1016/j.elecom.2012.10.009
    [Crossref], [CAS], Google Scholar
    27
    A redox shuttle to facilitate oxygen reduction in the lithium air battery
    Lacey, Matthew J.; Frith, James T.; Owen, John R.
    Electrochemistry Communications (2013), 26 (), 74-76CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
    A novel design of the non-aq. lithium air cell is presented with a demonstration of a new reaction concept, involving a sol. redox shuttle to catalyze oxygen redn. In principle, this can relieve the requirement for fast diffusion of mol. oxygen from the air interface to the pos. electrode. To demonstrate this concept, Et viologen ditriflate was dissolved in BMPTFSI, reduced at a carbon electrode and regenerated by aspiration with oxygen. Useful shuttle behavior, confirmed by several redn.-oxidn. cycles, was obsd. in the case where the electrolyte contained at least 0.3 M lithium salt. The beneficial effect of the salt was attributed to its crit. role in converting superoxide, which would otherwise destroy the shuttle, into the more desirable product of oxygen redn., lithium peroxide.
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  28. 28
    Lim, H. D.; Lee, B.; Zheng, Y.; Hong, J.; Kim, J.; Gwon, H.; Ko, Y.; Lee, M.; Cho, K.; Kang, K. Rational Design of Redox Mediators for Advanced Li-O2 Batteries. Nat. Energy 2016, 1, 16066,  DOI: 10.1038/nenergy.2016.66
    [Crossref], [CAS], Google Scholar
    28
    Rational design of redox mediators for advanced Li-O2 batteries
    Lim, Hee-Dae; Lee, Byungju; Zheng, Yongping; Hong, Jihyun; Kim, Jinsoo; Gwon, Hyeokjo; Ko, Youngmin; Lee, Minah; Cho, Kyeongjae; Kang, Kisuk
    Nature Energy (2016), 1 (6), 16066CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
    The discovery of effective catalysts is an important step towards achieving Li-O2 batteries with long cycle life and high round-trip efficiency. Sol.-type catalysts or redox mediators (RMs) possess great advantages over conventional solid catalysts, generally exhibiting much higher efficiency. Here, we select a series of org. RM candidates as a model system to identify the key descriptor in detg. the catalytic activities and stabilities in Li-O2 cells. It is revealed that the level of ionization energies, readily available parameters from a database of the mols., can serve such a role when comparing with the formation energy of Li2O2 and the HOMO energy of the electrolyte. It is demonstrated that they are crit. in reducing the overpotential and improving the stability of Li-O2 cells, resp. Accordingly, we propose a general principle for designing feasible catalysts and report a RM, dimethylphenazine, with a remarkably low overpotential and high stability.
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  29. 29
    Gao, X.; Chen, Y.; Johnson, L.; Bruce, P. G. Promoting Solution Phase Discharge in Li-O2 Batteries Containing Weakly Solvating Electrolyte Solutions. Nat. Mater. 2016, 15, 882– 888,  DOI: 10.1038/nmat4629
    [Crossref], [PubMed], [CAS], Google Scholar
    29
    Promoting solution phase discharge in Li-O2 batteries containing weakly solvating electrolyte solutions
    Gao, Xiangwen; Chen, Yuhui; Johnson, Lee; Bruce, Peter G.
    Nature Materials (2016), 15 (8), 882-888CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    On discharge, the Li-O2 battery can form a Li2O2 film on the cathode surface, leading to low capacities, low rates and early cell deactivation, or it can form Li2O2 particles in soln., leading to high capacities at relatively high rates and avoiding early cell deactivation. Achieving discharge in soln. is important and may be encouraged by the use of high donor or acceptor no. solvents or salts that dissolve the LiO2 intermediate involved in the formation of Li2O2. However, the characteristics that make high donor or acceptor no. solvents good (for example, high polarity) result in them being unstable towards LiO2 or Li2O2. Here we demonstrate that introduction of the additive 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) promotes soln. phase formation of Li2O2 in low-polarity and weakly solvating electrolyte solns. Importantly, it does so while simultaneously suppressing direct redn. to Li2O2 on the cathode surface, which would otherwise lead to Li2O2 film growth and premature cell death. It also halves the overpotential during discharge, increases the capacity 80- to 100-fold and enables rates >1 mA cmareal-2 for cathodes with capacities of >4 mAh cmareal-2. The DBBQ additive operates by a new mechanism that avoids the reactive LiO2 intermediate in soln.
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  30. 30
    Li, Y.; Zhang, Z.; Duan, D.; Sun, Y.; Wei, G.; Hao, X.; Liu, S.; Han, Y.; Meng, W. The Correlation of the Properties of Pyrrolidinium-Based Ionic Liquid Electrolytes with the Discharge–Charge Performances of Rechargeable Li–O2 Batteries. J. Power Sources 2016, 329, 207– 215,  DOI: 10.1016/j.jpowsour.2016.08.077
    [Crossref], [CAS], Google Scholar
    30
    The correlation of the properties of pyrrolidinium-based ionic liquid electrolytes with the discharge-charge performances of rechargeable Li-O2 batteries
    Li, Yu; Zhang, Zhonglin; Duan, Donghong; Sun, Yanbo; Wei, Guoqiang; Hao, Xiaogang; Liu, Shibin; Han, Yunxia; Meng, Weijuan
    Journal of Power Sources (2016), 329 (), 207-215CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Pyrrolidinium-based ionic liqs. (ILs), such as PYR13TFSI, PYR14TFSI, and PYR1(2O1)TFSI, exhibit high thermal and electrochem. stability with wide electrochem. windows as electrolytes for application to rechargeable Li-O2 batteries. Here, several fundamental properties of 3 ILs are measured: the ionic cond., O soly., and O diffusion coeff. The O electro-redn. kinetics is characterized using cyclic voltammetry. The performances of Li-O2 batteries with these IL electrolytes are also studied using electrochem. impedance spectroscopy and galvanostatic discharge-charge tests. The results demonstrate that the PYR1(2O1)TFSI electrolyte battery has a higher 1st-discharge voltage than the PYR13TFSI electrolyte and PYR14TFSI electrolyte batteries. Both PYR13TFSI- and PYR1(2O1)TFSI-based batteries exhibit higher 1st-discharge capacities and better cycling stabilities than the PYR14TFSI-based battery for 30 cycles. A theor. anal. of the exptl. results shows that the diffusion coeff. and soly. of O in the electrolyte remarkably affect the discharge capacity and cycling stability of the batteries. Particularly, the O diffusion coeff. of the IL electrolyte can effectively facilitate the electrochem. O electro-redn. reaction and O concn. distribution in the catalyst layers of air electrodes. The O diffusion coeff. and O soly. improvements of IL electrolytes can enhance the discharge-charge performances of Li-O2 batteries.
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  31. 31
    Wu, C.; Li, T.; Liao, C.; Xu, Q.; Cao, Y.; Li, L.; Yang, J. Enhanced Electrochemical Performance of Non-Aqueous Li–O2 Batteries with Triethylene Glycol Dimethyl Ether-Based Electrolyte. J. Electrochem. Soc. 2017, 164, A1321– A1327,  DOI: 10.1149/2.0251707jes
    [Crossref], [CAS], Google Scholar
    31
    Enhanced Electrochemical Performance of Non-Aqueous Li-O2 Batteries with Triethylene Glycol Dimethyl Ether-Based Electrolyte
    Wu, Chaolumen; Li, Taoran; Liao, Chenbo; Xu, Qingkai; Cao, Yuancheng; Li, Lei; Yang, Jun
    Journal of the Electrochemical Society (2017), 164 (6), A1321-A1327CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    Triethylene glycol di-Me ether (G3) is evaluated as an electrolyte solvent for non-aq. lithium-oxygen (Li-O2) batteries. A liq. electrolyte of 1 M LiTFSI in G3 shows lower viscosity, higher oxygen soly. and diffusion, higher ionic cond. and lithium ionic transference no. compared to the conventional liq. electrolyte of 1 M LiTFSI in tetraethylene glycol di-Me ether (G4). Then the Li-O2 battery using the G3-based electrolyte shows better cycling stability and higher rate capability compared to the battery using the G4-based electrolyte. At a higher c.d. of 2.5 A gcarbon-1, the discharge capacity of the battery using the G3-based electrolyte is about 1472 mAh gcarbon-1, which is about four times higher than that of the battery using the G4-based electrolyte. At c.d. of 1 A gcarbon-1 with a fixed capacity of 1000 mAh gcarbon-1, the battery using the G3-based electrolyte can be operated stably for 80 cycles, while only 20 cycles are achieved by using the G4-based electrolyte. Therefore, the G3-based electrolyte could be a proper alternative electrolyte to the conventional G4-based electrolyte for the development of Li-O2 batteries.
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  32. 32
    Cui, Y.; Wen, Z.; Liang, X.; Lu, Y.; Jin, J.; Wu, M.; Wu, X. A Tubular Polypyrrole Based Air Electrode with Improved O2 Diffusivity for Li-O2 Batteries. Energy Environ. Sci. 2012, 5, 7893– 7897,  DOI: 10.1039/c2ee21638h
    [Crossref], [CAS], Google Scholar
    32
    A tubular polypyrrole based air electrode with improved O2 diffusivity for Li-O2 batteries
    Cui, Yanming; Wen, Zhaoyin; Liang, Xiao; Lu, Yan; Jin, Jun; Wu, Meifen; Wu, Xiangwei
    Energy & Environmental Science (2012), 5 (7), 7893-7897CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
    A highly reversible air electrode was designed based on the hydrophilic nano-PPy tubes with abundant gas diffusion channels and reaction space which greatly improved the cell capacity, cycling stability and esp. the rate performance of the lithium-oxygen batteries.
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  33. 33
    Li, X.; Huang, J.; Faghri, A. Modeling Study of a Li-O2 Battery with an Active Cathode. Energy 2015, 81, 489– 500,  DOI: 10.1016/j.energy.2014.12.062
    [Crossref], [CAS], Google Scholar
    33
    Modeling study of a Li-O2 battery with an active cathode
    Li, Xianglin; Huang, Jing; Faghri, Amir
    Energy (Oxford, United Kingdom) (2015), 81 (), 489-500CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    In this study, a new org. lithium oxygen (Li-O2) battery structure is proposed to enhance battery capacity. The electrolyte is forced to recirculate through the cathode and then satd. with oxygen in a tank external to the battery. The forced convection enhances oxygen transport and alleviates the problem of electrode blockage during discharge. A two dimensional, transient, non-isothermal simulation model is developed to study the heat and mass transfer within the battery and validate the proposed design. Results show that this novel active cathode design improves the battery capacity at all discharge current densities. The capacity of the Li-O2 battery is increased by 15.5 times (from 12.2 mAh g-1 to 201 mAh g-1) at the discharge current of 2.0 mA cm-2 when a conventional passive electrode is replaced by the newly designed active electrode. Furthermore, a cathode with non-uniform porosity is suggested and simulation results show that it can reach a higher discharge capacity without decreasing its power d. Detailed mass transport processes in the battery are also studied.
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  34. 34
    Wang, F.; Xu, Y. H.; Luo, Z. K.; Pang, Y.; Wu, Q. X.; Liang, C. S.; Chen, J.; Liu, D.; Zhang, X. H. A Dual Pore Carbon Aerogel Based Air Cathode for a Highly Rechargeable Lithium-Air Battery. J. Power Sources 2014, 272, 1061– 1071,  DOI: 10.1016/j.jpowsour.2014.08.126
    [Crossref], [CAS], Google Scholar
    34
    A dual pore carbon aerogel-based air cathode for a highly rechargeable lithium-air battery
    Wang, Fang; Xu, Yang-Hai; Luo, Zhong-Kuan; Pang, Yan; Wu, Qi-Xing; Liang, Chun-Sheng; Chen, Jing; Liu, Dong; Zhang, Xiang-hua
    Journal of Power Sources (2014), 272 (), 1061-1071CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
    Cathode structure plays a vital role in Li-air battery for that it can provide space for discharged products accommodation and free path for O, e- and Li+ transport. However, pore blockage, cathode passivation and degrdn. all result in low discharge rates and poor cycling capability. To get rid of these problems, a novel highly conductive dual pore C aerogel based air cathode is fabricated to construct a Li-air battery, which exhibits 18 to 525 cycles in the LiTFSI/sulfolane electrolyte at a c.d. varying from 1.00 mA cm-2 to 0.05 mA cm-2, accompanied by a high energy efficiency of 78.32%. The authors postulate that the essence lies in that the as-prepd. air cathode inventively create a suitable tri-phase boundary reaction zone, facilitating O and Li+ diffusion in 2 independent pore channels, thus realizing a relative higher discharge rate capability, lower pore blockage and cathode passivation. Further, pore structure, C loading, rate capability, discharge depth and the air's effect are exploited and coordinated, targeting for a high power and reversible Li-air battery. Such nanoporous C aerogel air cathode of novel dual pore structure and material design is expected to be an attractive alternative for Li-air batteries and other Li based batteries.
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  35. 35
    Forse, A. C.; Griffin, J. M.; Merlet, C.; Carretero-Gonzalez, J.; Raji, A.-R. O.; Trease, N. M.; Grey, C. P. Direct Observation of Ion Dynamics in Supercapacitor Electrodes Using in Situ Diffusion NMR Spectroscopy. Nat. Energy 2017, 2, 16216,  DOI: 10.1038/nenergy.2016.216
    [Crossref], [CAS], Google Scholar
    35
    Direct observation of ion dynamics in supercapacitor electrodes using in situ diffusion NMR spectroscopy
    Forse, Alexander C.; Griffin, John M.; Merlet, Celine; Carretero-Gonzalez, Javier; Raji, Abdul-Rahman O.; Trease, Nicole M.; Grey, Clare P.
    Nature Energy (2017), 2 (2), 16216/1-16216/7CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
    Ionic transport inside porous carbon electrodes underpins the storage of energy in supercapacitors and the rate at which they can charge and discharge, yet few studies have elucidated the materials properties that influence ion dynamics. Here we use in situ pulsed field gradient NMR spectroscopy to measure ionic diffusion in supercapacitors directly. We find that confinement in the nanoporous electrode structures decreases the effective self-diffusion coeffs. of ions by over two orders of magnitude compared with neat electrolyte, and in-pore diffusion is modulated by changes in ion populations at the electrode/electrolyte interface during charging. Electrolyte concn. and carbon pore size distributions also affect in-pore diffusion and the movement of ions in and out of the nanopores. In light of our findings we propose that controlling the charging mechanism may allow the tuning of the energy and power performances of supercapacitors for a range of different applications.
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  36. 36
    Engelke, S.; Marbella, L. E.; Trease, N. M.; De Volder, M.; Grey, C. P. Three-Dimensional Pulsed Field Gradient NMR Measurements of Self-Diffusion in Anisotropic Materials for Energy Storage Applications. Phys. Chem. Chem. Phys. 2019, 21, 4538– 4546,  DOI: 10.1039/C8CP07776B
    [Crossref], [PubMed], [CAS], Google Scholar
    36
    Three-dimensional pulsed field gradient NMR measurements of self-diffusion in anisotropic materials for energy storage applications
    Engelke, S.; Marbella, L. E.; Trease, N. M.; De Volder, M.; Grey, C. P.
    Physical Chemistry Chemical Physics (2019), 21 (8), 4538-4546CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Anisotropic battery electrodes that allow enhanced diffusion through the thickness of the electrode can be engineered to improve the rate performance, but direct measurement of 3D diffusion in this pore structure is extremely challenging. To address this, we used 1H and 7Li pulsed field gradient (PFG) NMR to measure anisotropic diffusion in a model porous silicon substrate. We show that NMR spectroscopy can resolve solvent mols. and ions (here, in H2O, DMSO, and the battery electrolyte LIPF6:DC:EMC) in and outside of the pores of the Si substrate, allowing the diffusion coeffs. of the ion/mols. in the two components to be individually detd. Exchange between ions/mols. inside and outside of the pores is obsd. with 1H 2D exchange spectroscopy (EXSY). The pore dimensions can extd. from the diffusivity of the in-pore component and the results are in reasonable agreement with the pore dimensions measured with electron microscopy. Better agreement is obtained for pore diams.; for pore length measurements, exchange between the in-pore and ex-pore solvents should be accounted for. These results suggest that PFG-NMR can serve as a non-destructive characterization method for both in situ and ex situ analyses of materials ranging from complex battery and supercapacitor electrodes to catalyst supports and tissue scaffolds.
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  37. 37
    Stallmach, F.; Kärger, J.; Krause, C.; Jeschke, M.; Oberhagemann, U. Evidence of Anisotropic Self-Diffusion of Guest Molecules in Nanoporous Materials of MCM-41 Type. J. Am. Chem. Soc. 2000, 122, 9237– 9242,  DOI: 10.1021/ja001106x
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    37
    Evidence of Anisotropic Self-Diffusion of Guest Molecules in Nanoporous Materials of MCM-41 Type
    Stallmach, Frank; Kaerger, Joerg; Krause, Cordula; Jeschke, Markus; Oberhagemann, Uwe
    Journal of the American Chemical Society (2000), 122 (38), 9237-9242CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The pore architecture of MCM-41 was investigated by pulsed field gradient NMR (PFG NMR) self-diffusion measurements of adsorbed water. Over diffusion length scales which exceed the radius of the one-dimensional channels of the MCM-41 by 2 orders of magnitude but which are smaller than the size of the individual MCM-41 particles, the mol. propagation of the guest mols. was found to be highly anisotropic. The PFG NMR exptl. data are best represented by an axisym. diffusion tensor rather than by pure one-dimensional diffusion along the channels. This suggests that the pore walls of the one-dimensional channels are permeable for water or that over the probed diffusion length the channels are disordered and bent. Both interpretations provide information on the pore structure of the nanoporous material which is not available from X-ray diffraction data.
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  38. 38
    Kondrashova, D.; Lauerer, A.; Mehlhorn, D.; Jobic, H.; Feldhoff, A.; Thommes, M.; Chakraborty, D.; Gommes, C.; Zecevic, J.; De Jongh, P. Scale-Dependent Diffusion Anisotropy in Nanoporous Silicon. Sci. Rep. 2017, 7, 1– 10,  DOI: 10.1038/srep40207
    [Crossref], [PubMed], [CAS], Google Scholar
    38
    Phase transitions in disordered mesoporous solids
    Schneider, Daniel; Kondrashova, Daria; Valiullin, Rustem
    Scientific Reports (2017), 7 (1), 1-13CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)
    Fluids confined in mesoporous solids exhibit a wide range of phys. behavior including rich phase equil. While a notable progress in their understanding has been achieved for fluids in materials with geometrically ordered pore systems, mesoporous solids with complex pore geometries still remain a topic of active research. In this work we study phase transitions occurring in statistically disordered linear chains of pores with different pore sizes. By considering, quite generally, two phase change mechanisms, nucleation and phase growth, occurring simultaneously we obtain the boundary transitions and the scanning curves resulting upon reversing the sign of the evolution of the chem. potential at different points along the main transition branches. The results obtained are found to reproduces the key exptl. observations, including the emergence of hysteresis and the scanning behavior. By deriving the serial pore model isotherm we suggest a robust framework for reliable structural anal. of disordered mesoporous solids.
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  39. 39
    Torayev, A.; Rucci, A.; Magusin, P. C. M. M.; Demortière, A.; De Andrade, V.; Grey, C. P.; Merlet, C.; Franco, A. A. Stochasticity of Pores Interconnectivity in Li-O2 Batteries and Its Impact on the Variations in Electrochemical Performance. J. Phys. Chem. Lett. 2018, 9, 791– 797,  DOI: 10.1021/acs.jpclett.7b03315
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    39
    Stochasticity of Pores Interconnectivity in Li-O2 Batteries and its Impact on the Variations in Electrochemical Performance
    Torayev, Amangeldi; Rucci, Alexis; Magusin, Pieter C. M. M.; Demortiere, Arnaud; De Andrade, Vincent; Grey, Clare P.; Merlet, Celine; Franco, Alejandro A.
    Journal of Physical Chemistry Letters (2018), 9 (4), 791-797CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    While large dispersions in electrochem. performance have been reported for lithium oxygen batteries in the literature, they have not been investigated in any depth. The variability in the results is often assumed to arise from differences in cell design, electrode structure, handling and cell prepn. at different times. An accurate theor. framework turns out to be needed to get a better insight into the mechanisms underneath and to interpret exptl. results. Here, we develop and use a pore network model to simulate the electrochem. performance of three-dimensionally resolved lithium-oxygen cathode mesostructures obtained from TXM nanocomputed tomog. We apply this model to the 3D reconstructed object of a Super P carbon electrode and calc. discharge curves, using identical conditions, for four different zones in the electrode and their reversed configurations. The resulting galvanostatic discharge curves show some dispersion, (both in terms of capacity and overpotential) which we attribute to the way pores are connected with each other. Based on these results, we propose that the stochastic nature of pore interconnectivity and the microscopic arrangement of pores can lead, at least partially, to the variations in electrochem. results obsd. exptl.
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  40. 40
    Torayev, A.; Magusin, P. C. M. M.; Grey, C. P.; Merlet, C.; Franco, A. A. Importance of Incorporating Explicit 3D-Resolved Electrode Mesostructures in Li–O2 Battery Models. ACS Appl. Energy Mater. 2018, 1, 6433– 6441,  DOI: 10.1021/acsaem.8b01392
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Stejskal, E. O.; Tanner, J. E. Spin Diffusion Measurements: Spin Echoes in the Presence of a Time-Dependent Field Gradient. J. Chem. Phys. 1965, 42, 288– 292,  DOI: 10.1063/1.1695690
    [Crossref], [CAS], Google Scholar
    41
    Spin diffusion measurements: spin echoes in the presence of a time-dependent field gradient
    Stejskal, E. O.; Tanner, J. E.
    Journal of Chemical Physics (1965), 42 (1), 288-92CODEN: JCPSA6; ISSN:0021-9606.
    A derivation is given of the effect of a time-dependent magnetic field gradient on the spin-echo expt., particularly in the presence of spin diffusion. There are several reasons for preferring certain kinds of time-dependent magnetic field gradients to the more usual steady gradient. If the gradient is reduced during the radio-frequency pulses, H1 need not be particularly large; if the gradient is small at the time of the echo, the echo will be broad and its amplitude easy to measure. Both of these relaxations of restrictions on the measurement of diffusion coeffs. by the spin-echo technique serve to extend its range of applicability. A pulsed gradient can be recommended when it is crit. to define the precise time period over which diffusion is being measured. The theoretical expression derived was verified exptl. for several choices of time-dependent magnetic field gradient. An app. is described suitable for the production of pulsed gradients with amplitudes as large as 100 gauss cm. The diffusion coeff. of dry glycerol at 26° ± 1° is (2.5 ± 0.2) × 10-3 cm.2/sec., a value smaller than can ordinarily be measured by the steady gradient method.
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  42. 42
    Price, W. S. NMR Studies of Translational Motion; Cambridge University Press: Cambridge, 2009,  DOI: 10.1017/CBO9780511770487 .
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  43. 43
    Chung, D.-W.; Ebner, M.; Ely, D. R.; Wood, V.; Edwin García, R. Validity of the Bruggeman Relation for Porous Electrodes. Modell. Simul. Mater. Sci. Eng. 2013, 21, 074009  DOI: 10.1088/0965-0393/21/7/074009
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  44. 44
    De Andrade, V.; Deriy, A.; Wojcik, M. J.; Gürsoy, D.; Shu, D.; Fezzaa, K.; De Carlo, F. Nanoscale 3D Imaging at the Advanced Photon Source. SPIE Newsroom 2016, 006461  DOI: 10.1117/2.1201604.006461
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  45. 45
    Su, Z.; De Andrade, V.; Cretu, S.; Yin, Y.; Wojcik, M. J.; Franco, A. A.; Demortière, A. X-Ray Nanocomputed Tomography in Zernike Phase Contrast for Studying 3D Morphology of Li–O2 Battery Electrode. ACS Appl. Energy Mater. 2020, 3, 4093– 4102,  DOI: 10.1021/acsaem.9b02236
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    45
    X-ray Nanocomputed Tomography in Zernike Phase Contrast for Studying 3D Morphology of Li-O2 Battery Electrode
    Su, Zeliang; De Andrade, Vincent; Cretu, Sorina; Yin, Yinghui; Wojcik, Michael J.; Franco, Alejandro A.; Demortiere, Arnaud
    ACS Applied Energy Materials (2020), 3 (5), 4093-4102CODEN: AAEMCQ; ISSN:2574-0962. (American Chemical Society)
    The lithium peroxide (Li2O2) and pore size distribution are investigated in lithium-O2 battery electrodes at different states of charge using transmission X-ray microscopy coupled with Zernike phase contrast to carry out nanocomputed tomog. It is reported that such a technique enables, at the nanoscale, to distinguish light elements such as carbon and Li2O2 in Li-O2 battery cathode electrodes. It is verified by wave-propagation simulation that this approach efficiently improves the contrast of images in comparison with pure absorption. The Li2O2 distribution and thickness, interphases, and pore network are visualized and quantified, giving a valuable insight into the cathode architecture. From this 3D anal., modifications are highlighted of the air-cathode morphol. and the Li2O2 spatial organization as well as their potential implication in terms of carbon surface passivation and pore-clogging. After the full recharge process, this technique can also reveal the spatial distribution of the residual Li2O2 and other byproducts.
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  46. 46
    Gürsoy, D.; De Carlo, F.; Xiao, X.; Jacobsen, C. TomoPy: A Framework for the Analysis of Synchrotron Tomographic Data. J. Synchrotron Radiat. 2014, 21, 1188– 1193,  DOI: 10.1107/S1600577514013939
    [Crossref], [PubMed], [CAS], Google Scholar
    46
    TomoPy: a framework for the analysis of synchrotron tomographic data
    Gursoy Doga; De Carlo Francesco; Xiao Xianghui; Jacobsen Chris
    Journal of synchrotron radiation (2014), 21 (Pt 5), 1188-93 ISSN:.
    Analysis of tomographic datasets at synchrotron light sources (including X-ray transmission tomography, X-ray fluorescence microscopy and X-ray diffraction tomography) is becoming progressively more challenging due to the increasing data acquisition rates that new technologies in X-ray sources and detectors enable. The next generation of synchrotron facilities that are currently under design or construction throughout the world will provide diffraction-limited X-ray sources and are expected to boost the current data rates by several orders of magnitude, stressing the need for the development and integration of efficient analysis tools. Here an attempt to provide a collaborative framework for the analysis of synchrotron tomographic data that has the potential to unify the effort of different facilities and beamlines performing similar tasks is described in detail. The proposed Python-based framework is open-source, platform- and data-format-independent, has multiprocessing capability and supports procedural programming that many researchers prefer. This collaborative platform could affect all major synchrotron facilities where new effort is now dedicated to developing new tools that can be deployed at the facility for real-time processing, as well as distributed to users for off-site data processing.
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  47. 47
    Pelt, D. M.; Gürsoy, D.; Palenstijn, W. J.; Sijbers, J.; De Carlo, F.; Batenburg, K. J. Integration of TomoPy and the ASTRA Toolbox for Advanced Processing and Reconstruction of Tomographic Synchrotron Data. J. Synchrotron Radiat. 2016, 23, 842– 849,  DOI: 10.1107/S1600577516005658
    [Crossref], [PubMed], [CAS], Google Scholar
    47
    Integration of TomoPy and the ASTRA toolbox for advanced processing and reconstruction of tomographic synchrotron data
    Pelt, Daniel M.; Guersoy, Doga; Palenstijn, Willem Jan; Sijbers, Jan; De Carlo, Francesco; Batenburg, Kees Joost
    Journal of Synchrotron Radiation (2016), 23 (3), 842-849CODEN: JSYRES; ISSN:1600-5775. (International Union of Crystallography)
    The processing of tomog. synchrotron data requires advanced and efficient software to be able to produce accurate results in reasonable time. In this paper, the integration of two software toolboxes, TomoPy and the ASTRA toolbox, which, together, provide a powerful framework for processing tomog. data, is presented. The integration combines the advantages of both toolboxes, such as the user-friendliness and CPU-efficient methods of TomoPy and the flexibility and optimized GPU-based reconstruction methods of the ASTRA toolbox. It is shown that both toolboxes can be easily installed and used together, requiring only minor changes to existing TomoPy scripts. Furthermore, it is shown that the efficient GPU-based reconstruction methods of the ASTRA toolbox can significantly decrease the time needed to reconstruct large datasets, and that advanced reconstruction methods can improve reconstruction quality compared with TomoPy's std. reconstruction method.
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  48. 48
    Arganda-Carreras, I.; Kaynig, V.; Rueden, C.; Eliceiri, K. W.; Schindelin, J.; Cardona, A.; Sebastian Seung, H. Trainable Weka Segmentation: A Machine Learning Tool for Microscopy Pixel Classification. Bioinformatics 2017, 33, 2424– 2426,  DOI: 10.1093/bioinformatics/btx180
    [Crossref], [PubMed], [CAS], Google Scholar
    48
    Trainable Weka Segmentation: a machine learning tool for microscopy pixel classification
    Arganda-Carreras, Ignacio; Kaynig, Verena; Rueden, Curtis; Eliceiri, Kevin W.; Schindelin, Johannes; Cardona, Albert; Seung, H. Sebastian
    Bioinformatics (2017), 33 (15), 2424-2426CODEN: BOINFP; ISSN:1460-2059. (Oxford University Press)
    State-of-the-art light and electron microscopes are capable of acquiring large image datasets, but quant. evaluating the data often involves manually annotating structures of interest. This process is time-consuming and often a major bottleneck in the evaluation pipeline. To overcome this problem, we have introduced the Trainable Weka Segmentation (TWS), a machine learning tool that leverages a limited no. of manual annotations in order to train a classifier and segment the remaining data automatically. In addn., TWS can provide unsupervised segmentation learning schemes (clustering) and can be customized to employ user-designed image features or classifiers.
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  49. 49
    Cooper, S. J.; Bertei, A.; Shearing, P. R.; Kilner, J. A.; Brandon, N. P. TauFactor: An Open-Source Application for Calculating Tortuosity Factors from Tomographic Data. SoftwareX 2016, 5, 203– 210,  DOI: 10.1016/j.softx.2016.09.002
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  50. 50
    Blanquer, G.; Yin, Y.; Quiroga, M. A.; Franco, A. A. Modeling Investigation of the Local Electrochemistry in Lithium-O2 Batteries: A Kinetic Monte Carlo Approach. J. Electrochem. Soc. 2016, 163, A329– A337,  DOI: 10.1149/2.0841602jes
    [Crossref], [CAS], Google Scholar
    50
    Modeling Investigation of the Local Electrochemistry in Lithium-O2 Batteries: A Kinetic Monte Carlo Approach
    Blanquer, Guillaume; Yin, Yinghui; Quiroga, Matias A.; Franco, Alejandro A.
    Journal of the Electrochemical Society (2016), 163 (3), A329-A337CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    In this paper we present a mesoscopic model of the transport and electrochem. processes inside a Lithium-O2 battery cathode pore. The model dynamically resolves both Oxygen Redn. Reaction (ORR) thin film and soln. phase mechanisms together with the transport of O2, Li+ and LiO2 in the electrolyte. It is supported on an extension to three dimensions of our Kinetic Monte Carlo (KMC) Electrochem. Variable Step Size Method (E-VSSM) recently published by M. A. Quiroga and A. A. Franco (2015). The model allows predicting porosity evolution as a function of multiple operational, phys. and geometrical parameters including the pore size and inlet/outlet channel size, O2 and Li+ concn., the property of the solvent as well as the applied overpotential. The investigation of the impact of these different aspects reveals that at the mesoscale level, the overall ORR kinetics and the discharge mechanism strongly depend on a balance between the geometrical features of the pore and the transport as well as the electrochem. properties of the system.
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  51. 51
    Reuter, K. First-Principles Kinetic Monte Carlo Simulations for Heterogeneous Catalysis: Concepts, Status, and Frontiers. Modeling and Simulation of Heterogeneous Catalytic Reactions: From the Molecular Process to the Technical System; John Wiley & Sons, Ltd: 2011; 71– 111.
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  52. 52
    Griffith, L. D.; Sleightholme, A. E. S.; Mansfield, J. F.; Siegel, D. J.; Monroe, C. W. Correlating Li/O2 Cell Capacity and Product Morphology with Discharge Current. ACS Appl. Mater. Interfaces 2015, 7, 7670– 7678,  DOI: 10.1021/acsami.5b00574
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    52
    Correlating Li/O2 Cell Capacity and Product Morphology with Discharge Current
    Griffith, Lucas D.; Sleightholme, Alice E. S.; Mansfield, John F.; Siegel, Donald J.; Monroe, Charles W.
    ACS Applied Materials & Interfaces (2015), 7 (14), 7670-7678CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    The discharge rate is crit. to the performance of Li/O batteries: it impacts both cell capacity and discharge-phase morphol., and in so doing may also affect the efficiency of the O-evolution reaction during recharging. First-discharge data from tens of Li/O2 cells discharged across four rates are analyzed statistically to inform these connections. In the practically significant superficial current-d. range of 0.1 to 1 mA cm-2, capacity is found to fall as a power law, with a Peukert's-law exponent of 1.6 ± 0.1. X-ray diffractometry confirms the dominant presence of cryst. Li2O2 in the discharged electrodes. A completely air-free sample-transfer technique was developed to implement SEM of the discharge product. SEM imaging of electrodes with near-av. capacities provides statistically significant measures of the shape and size variation of electrodeposited Li2O2 particles with respect to discharge current. At lower rates, typical toroidal particles are obsd. that are well approximated as cylindrical structures, whose av. radii remain relatively const. as discharge rate increases, whereas their av. heights decrease. At the highest rate studied, air-free SEM shows that particles take needle-like shapes rather than forming the nanosheets or compact films described elsewhere. Av. particle vols. decrease with current while particle surface-to-vol. ratios increase dramatically, supporting the notion that Li2O2 grows by a locally mass-transfer-limited nucleation and growth mechanism.
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  53. 53
    Bruggeman, D. A. G. Berechnung Verschiedener Physikalischer Konstanten von Heterogenen Substanzen. I. Dielektrizitätskonstanten Und Leitfähigkeiten Der Mischkörper Aus Isotropen Substanzen. Ann. Phys. 1935, 416, 636– 664,  DOI: 10.1002/andp.19354160705
    [Crossref], Google Scholar
    There is no corresponding record for this reference.

Cited By

This article is cited by 3 publications.

  1. Kee Sung Han, J. David Bazak, Ying Chen, Trent R. Graham, Nancy M. Washton, Jian Zhi Hu, Vijayakumar Murugesan, Karl T. Mueller. Pulsed Field Gradient Nuclear Magnetic Resonance and Diffusion Analysis in Battery Research. Chemistry of Materials 2021, 33 (22) , 8562-8590. https://doi.org/10.1021/acs.chemmater.1c02891
  2. Zhuojun Zhang, Xu Xiao, Wentao Yu, Zhongxi Zhao, Peng Tan. Modeling of a non-aqueous Li-O2 battery incorporating synergistic reaction mechanisms, microstructure, and species transport in the porous electrode. Electrochimica Acta 2022, 421 , 140510. https://doi.org/10.1016/j.electacta.2022.140510
  3. Xiaohong Zou, Qian Lu, Kaiming Liao, Zongping Shao. Towards practically accessible aprotic Li-air batteries: Progress and challenges related to oxygen-permeable membranes and cathodes. Energy Storage Materials 2022, 45 , 869-902. https://doi.org/10.1016/j.ensm.2021.12.031

  • Abstract

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    Figure 1

    Figure 1. (a) Scheme of the Swagelok cell used for the electrochemical experiments. (b) The glass chamber used to keep the Swagelok cells under oxygen, which has space for a single Swagelok cell.

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    Figure 2

    Figure 2. Pulse sequence used for the stimulated echo-pulsed field gradient NMR experiments: (top) NMR frequency pulses and (bottom) gradient pulses.

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    Figure 3

    Figure 3. (a) Illustration of the area covered by a diffusing molecule with time. (b) Schematic representation of free diffusion and confined diffusion as a function of diffusion time.

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    Figure 4

    Figure 4. Cylindrical pore geometry considered in the kMC model.

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    Figure 5

    Figure 5. Illustration of the determination of a diffusion coefficient from an MSD curve. Two vertical lines show the time interval where the MSD curve is linear with time. The red line is the fit to the MSD curve in the selected region.

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    Figure 6

    Figure 6. Diffusion coefficients for bulk tetraglyme and tetraglyme in three Super P electrodes, determined with PFG methods as a function of diffusion time, Δ.

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    Figure 7

    Figure 7. Tetraglyme diffusion in self-standing Super P electrodes as a probe for pore clogging at various states of discharge against lithium. (a) Constant 50 μA current discharge profiles of Super P with 0.5 M LiTFSI-tetraglyme as electrolyte. (b, c) Diffusion NMR of Super P electrodes discharged in (b) DME and (c) tetraglyme. 1H PFG NMR echo decays vs the composed experimental parameter γ2gz2δ2(Δ – δ/3) (eq 2) increasingly deviate from monoexponential behavior (dashed lines) at increasing depth of discharge. The data are well described in terms of a biexponential model (solid lines) with two discharge-constant diffusion coefficients and fractions, which vary with discharge. Phenomenologically, the two fractions represent the clog-free and clogged electrode parts. (d) Effective tetraglyme diffusion coefficients (a weighted average of the two diffusion coefficients) in self-standing Super P electrodes discharged with either DME or tetraglyme as electrolytes as a function of discharge. Dashed lines are a guide to the eye. The PFG NMR data shown here have been recorded for a diffusion time Δ = 1200 ms. For PFG echo decays at different Δ times, see Figure S5.

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    Figure 8

    Figure 8. Diffusion coefficients pairs (DA, DB) extracted from bicomponent fits to PFG decays as a function of the diffusion time for an electrode discharged in DME (left) and tetraglyme (right). The biexponential model assumes that the values of the diffusion coefficients do not change with the discharge stage, but the relative fraction of each component does. Changes in pore clogging are reflected by the fraction of each component (Table 1).

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    Figure 9

    Figure 9. Tortuosity factors in pristine, partially, and fully discharged self-standing Super P electrodes, extracted from PFG-NMR measurements using weighted average diffusion coefficients from the biexponential model. The solvent used for discharge is indicated in the legend. The Bruggeman relation is applied by assuming that all discharge products are Li2O2. Dashed lines for experimental data are linear fit to the data points weighted with the error bars. An explanation of the error analysis is given in the Supporting Information.

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    Figure 10

    Figure 10. Pore size distributions obtained from tomographic images of (a) partially 206 mAh g–1 and (b) fully 362 mAh g–1 discharged Super P electrodes with 0.5 M LiTFSI, tetraglyme electrolytes at 50 μA discharge current.

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    Figure 11

    Figure 11. Number of clogged pores for the Super P electrode structure calculated using PNM modelling of the pristine Super P electrode structure obtained from tomographic imaging. The discharge current density is 100 μA g–1. Plots are shown for five escape factors (χ =0, 0.25, 0.5, 0.75, and 1).

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    Figure 12

    Figure 12. MSD plots obtained from kMC calculations for several pore sizes.

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    Figure 13

    Figure 13. O2 diffusion coefficients calculated using the kMC model for various pore diameters.

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  • References

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    This article references 53 other publications.

    1. 1
      Abraham, K. M.; Jiang, Z. A Polymer Electrolyte-Based Rechargeable Lithium/Oxygen Battery. J. Electrochem. Soc. 1996, 143, 1– 5,  DOI: 10.1149/1.1836378
      [Crossref], [CAS], Google Scholar
      1
      A polymer electrolyte-based rechargeable lithium/oxygen battery
      Abraham, K. M.; Jiang, Z.
      Journal of the Electrochemical Society (1996), 143 (1), 1-5CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      A novel rechargeable Li/O battery is described. The battery comprises a Li+ conductive org. polymer electrolyte membrane sandwiched by a thin Li metal foil anode and a thin carbon composite electrode on which oxygen, the electroactive cathode material, accessed from the environment, is reduced during discharge to generate elec. power. It features an all solid state design in which electrode and electrolyte layers are laminated to form a 200-300 μm thick battery cell. The overall cell reaction during discharge appears to be 2Li + O2 → Li2O2. The battery has an open-circuit voltage of ∼3 V, and a load voltage that spans between 2 and 2.8 V depending on the load resistance. The cell can be recharged with good coulombic efficiency using a cobalt phthalocyanine catalyzed carbon electrode.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XksVyisA%253D%253D&md5=d3b65ef8c2e3f23e97b2826f92c489da
    2. 2
      Ma, Z.; Yuan, X.; Li, L.; Ma, Z.-F.; Wilkinson, D. P.; Zhang, L.; Zhang, J. A Review of Cathode Materials and Structures for Rechargeable Lithium–Air Batteries. Energy Environ. Sci. 2015, 8, 2144– 2198,  DOI: 10.1039/C5EE00838G
      [Crossref], [CAS], Google Scholar
      2
      A review of cathode materials and structures for rechargeable lithium-air batteries
      Ma, Zhong; Yuan, Xianxia; Li, Lin; Ma, Zi-Feng; Wilkinson, David P.; Zhang, Lei; Zhang, Jiujun
      Energy & Environmental Science (2015), 8 (8), 2144-2198CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      Rechargeable lithium air (Li-air) batteries, esp. the non-aq. type, are considered the most promising energy storage and conversion device candidates for use in future elec. vehicle applications due to their ultrahigh energy d. The air cathode has been identified as a key factor affecting the overall performance of Li-air batteries. The current low level performance of air cathodes is the major challenge hindering com. applications of Li-air batteries. In the past decade, a great many cathode materials, structures and fabrication processes have been developed and investigated with the goal of enhancing cathode performance. This paper reviews, the role of the cathode in non-aq. Li-air batteries including the cathode reaction mechanisms and the properties and morphologies of cathode materials, followed by approaches to optimize cathode performance. The most recently published global progress and the main achievements in the field of Li-air batteries are also systematically and critically reviewed in terms of cathode materials, structures and fabrication processes, with the objective of providing some state-of-the-art information. Tech. challenges are analyzed, and insights into future research directions for overcoming these development challenges of rechargeable non-aq. Li-air battery cathodes are also identified in this review paper.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXpsF2ns70%253D&md5=d03bef812deda29539c56232a575af4b
    3. 3
      Viswanathan, V.; Thygesen, K. S.; Hummelshøj, J. S.; Nørskov, J. K.; Girishkumar, G.; McCloskey, B. D.; Luntz, A. C. Electrical Conductivity in Li2O2 and Its Role in Determining Capacity Limitations in Non-Aqueous Li-O2 Batteries. J. Chem. Phys. 2011, 135, 214704,  DOI: 10.1063/1.3663385
      [Crossref], [PubMed], [CAS], Google Scholar
      3
      Electrical conductivity in Li2O2 and its role in determining capacity limitations in non-aqueous Li-O2 batteries
      Viswanathan, V.; Thygesen, K. S.; Hummelshoj, J. S.; Norskov, J. K.; Girishkumar, G.; McCloskey, B. D.; Luntz, A. C.
      Journal of Chemical Physics (2011), 135 (21), 214704/1-214704/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Nonaq. Li-air or Li-O2 cells show considerable promise as a very high energy d. battery couple. Such cells, however, show sudden death at capacities far below their theor. capacity and this, among other problems, limits their practicality. This sudden death arises from limited charge transport through the growing Li2O2 film to the Li2O2-electrolyte interface, and this limitation defines a crit. film thickness, above which it is not possible to support electrochem. at the Li2O2-electrolyte interface. The authors report both electrochem. expts. using a reversible internal redox couple and a 1st principles metal-insulator-metal charge transport model to probe the elec. cond. through Li2O2 films produced during Li-O2 discharge. Both expt. and theory show a sudden death in charge transport when film thickness is ∼5 to 10 nm. The theor. model shows that this occurs when the tunneling current through the film can no longer support the electrochem. current. Thus, engineering charge transport through Li2O2 is a serious challenge if Li-O2 batteries are ever to reach their potential. (c) 2011 American Institute of Physics.
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    4. 4
      Yin, Y.; Torayev, A.; Gaya, C.; Mammeri, Y.; Franco, A. A. Linking the Performances of Li–O2 Batteries to Discharge Rate and Electrode and Electrolyte Properties through the Nucleation Mechanism of Li2O2. J. Phys. Chem. C 2017, 121, 19577– 19585,  DOI: 10.1021/acs.jpcc.7b05224
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      4
      Linking the Performances of Li-O2 Batteries to Discharge Rate and Electrode and Electrolyte Properties through the Nucleation Mechanism of Li2O2
      Yin, Yinghui; Torayev, Amangeldi; Gaya, Caroline; Mammeri, Youcef; Franco, Alejandro A.
      Journal of Physical Chemistry C (2017), 121 (36), 19577-19585CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Li-O2 batteries have attracted a lot of attention because of their high theor. capacity. Due to the high complexity of these systems, deep understanding of the discharge mechanism is still needed to push the state-of-the-art performance of Li-O2 batteries to the theor. one. A universal multiscale model combining nucleation theory, detailed reaction kinetics, and mass transport is presented in this article, which encompasses the impacts of discharge rate, electrolyte property and electrode surface properties on the discharge capacity of Li-O2 batteries and on the morphol. of the Li2O2 arising from its nucleation process.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlWnsLrJ&md5=17829f168d8e267f36326b299660de00
    5. 5
      Luntz, A. C.; Viswanathan, V.; Voss, J.; Varley, J. B.; Nørskov, J. K.; Scheffler, R.; Speidel, A. Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries. J. Phys. Chem. Lett. 2013, 4, 3494– 3499,  DOI: 10.1021/jz401926f
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      5
      Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries
      Luntz, A. C.; Viswanathan, V.; Voss, J.; Varley, J. B.; Noerskov, J. K.; Scheffler, R.; Speidel, A.
      Journal of Physical Chemistry Letters (2013), 4 (20), 3494-3499CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The authors describe Li-O2 discharge expts. in a bulk electrolysis cell as a function of c.d. and temp. In combination with a simple model, these imply that charge transport through Li2O2 in Li-O2 batteries at practical current densities is based principally on hole tunneling, with hole polaron cond. playing a significant role near the end of low current discharges and at temps. >30°. Also charge-transport limitations are less significant during charging than those in discharge. A key element of the model that qual. explains all results is the alignment of the Li2O2 valence band max. close to the electrochem. Fermi energy and how this alignment varies with overpotentials during discharge and charge. In fact, comparison of the model with the expts. allows detn. of the alignment of the bands relative to the electrochem. Fermi level.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsFGrsrnJ&md5=0d1aed59c61afdf7b5a7f6add6aa631e
    6. 6
      Mitchell, R. R.; Gallant, B. M.; Shao-Horn, Y.; Thompson, C. V. Mechanisms of Morphological Evolution of Li2O2 Particles during Electrochemical Growth. J. Phys. Chem. Lett. 2013, 4, 1060– 1064,  DOI: 10.1021/jz4003586
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      6
      Mechanisms of Morphological Evolution of Li2O2 Particles during Electrochemical Growth
      Mitchell, Robert R.; Gallant, Betar M.; Shao-Horn, Yang; Thompson, Carl V.
      Journal of Physical Chemistry Letters (2013), 4 (7), 1060-1064CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Li-O2 batteries, wherein solid Li2O2 is formed at the porous air cathode during discharge, are candidates for high gravimetric energy (3212 W-h/kgLi2O2 ) storage for elec. vehicles. Understanding and controlling the nucleation and morphol. evolution of Li2O2 particles upon discharge is key to achieving high volumetric energy densities. SEM and TEM were used to characterize the discharge product formed in Li-O2 batteries on electrodes composed of carpets of aligned C nanotubes. At low discharge rates, Li2O2 particles form 1st as stacked thin plates, ∼10 nm in thickness, which spontaneously splay so that secondary nucleation of new plates eventually leads to the development of a particle with a toroidal shape. Li2O2 crystallites have large (001) crystal faces consistent with the theor. Wulff shape and appear to grow by a layer-by-layer mechanism. But at high discharge rates, copious nucleation of equiaxed Li2O2 particles precedes growth of disks and toroids.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjvFWhsrg%253D&md5=e4402871229eb966c7e49daf520145c9
    7. 7
      Zhai, D.; Wang, H.-H.; Yang, J.; Lau, K. C.; Li, K.; Amine, K.; Curtiss, L. A. Disproportionation in Li-O2 Batteries Based on a Large Surface Area Carbon Cathode. J. Am. Chem. Soc. 2013, 135, 15364– 15372,  DOI: 10.1021/ja403199d
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      7
      Disproportionation in Li-O2 batteries based on a large surface area carbon cathode
      Zhai, Dengyun; Wang, Hsien-Hau; Yang, Junbing; Lau, Kah Chun; Li, Kaixi; Amine, Khalil; Curtiss, Larry A.
      Journal of the American Chemical Society (2013), 135 (41), 15364-15372CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      In this paper we report on a kinetics study of the discharge process and its relationship to the charge overpotential in a Li-O2 cell for large surface area cathode material. The kinetics study reveals evidence for a first-order disproportionation reaction during discharge from an oxygen-rich Li2O2 component with superoxide-like character to a Li2O2 component. The oxygen-rich superoxide-like component has a much smaller potential during charge (3.2-3.5 V) than the Li2O2 component (∼4.2 V). The formation of the superoxide-like component is likely due to the porosity of the activated carbon used in the Li-O2 cell cathode that provides a good environment for growth during discharge. The discharge product contg. these two components is characterized by toroids, which are assemblies of nanoparticles. The morphol. growth and decompn. process of the toroids during the reversible discharge/charge process was obsd. by SEM and is consistent with the presence of the two components in the discharge product. The results of this study provide new insight into how growth conditions control the nature of discharge product, which can be used to achieve improved performance in Li-O2 cell.
      >> More from SciFinder ®
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    8. 8
      Xue, K.-H.; McTurk, E.; Johnson, L.; Bruce, P. G.; Franco, A. A. A Comprehensive Model for Non-Aqueous Lithium Air Batteries Involving Different Reaction Mechanisms. J. Electrochem. Soc. 2015, 162, A614– A621,  DOI: 10.1149/2.0121504jes
      [Crossref], [CAS], Google Scholar
      8
      A Comprehensive Model for Non-Aqueous Lithium Air Batteries Involving Different Reaction Mechanisms
      Xue, Kan-Hao; McTurk, Euan; Johnson, Lee; Bruce, Peter G.; Franco, Alejandro A.
      Journal of the Electrochemical Society (2015), 162 (4), A614-A621CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      There are various reaction mechanisms in the discharge process of a nonaq. lithium-air battery. Recently, it has been identified that low current rate and high donor no. solvents can lead to soln. phase reaction, but high current rate and low donor no. solvents will cause thin film growth covering the active cathode surface. In this paper we extend our previous lithium-air battery multiscale model, which considers the thin film growth mode, to the general case where both surface thin film growth and soln. phase reaction coexist. A detailed mechanism is proposed and simulation results are compared with exptl. data.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjtVehtbs%253D&md5=fd0fe5735b49c3649a63866927c5d390
    9. 9
      Laoire, C. O.; Mukerjee, S.; Abraham, K. M.; Plichta, E. J.; Hendrickson, M. A. Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications. J. Phys. Chem. C 2009, 113, 20127– 20134,  DOI: 10.1021/jp908090s
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      9
      Elucidating the Mechanism of Oxygen Reduction for Lithium-Air Battery Applications
      Laoire, Cormac O.; Mukerjee, Sanjeev; Abraham, K. M.; Plichta, Edward J.; Hendrickson, Mary A.
      Journal of Physical Chemistry C (2009), 113 (46), 20127-20134CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The capabilities of a Li anode in a Li battery has until now been limited by the low capacity intercalation and conversion reactions at the cathodes. It is however possible to remove these electrodes and allow Li to react directly with O in the atm., forming a Li-air battery. The Li/O2 battery redox couple has a theor. sp. energy of 5200 W-h/kg and represents the ultimate, environmentally friendly electrochem. power source. The role of electrolyte, in particular the role of ion-conducting salts, in detg. the reversibility and kinetics of O redn. in nonaq. electrolytes was studied. Understanding of this high energy d. battery is crucial to harnessing its full energy potential. The kinetics and mechanisms of O2 redn. in solns. of hexafluorophosphate A+PF6-, where A = Bu4N (TBA), K, Na, and Li, in MeCN are reported on glassy C electrodes using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The cations in the electrolyte influence the redn. mechanism of O2. Larger cations represented by TBA salts displayed reversible O2/O2- redox couple, in contrast to those contg. the smaller Li (and other alkali metal) cations, where an irreversible 1-electron redn. of O2 to LiO2, and other alkali metal superoxides, occurs as the 1st process. It was also found that the LiO2 formed initially decomps. to Li2O2. Electrochem. data support the view that alkali metal oxides formed via electrochem. and chem. reactions passivate the electrode surface, making the processes irreversible. The O2 redn. mechanisms in the presence of the different cations have been supplemented by kinetic parameters detd. from detailed analyses of the CV and RDE data. The Lewis acid characteristics of the cation appear to be crucial in detg. the reversibility of the system. These results can contribute to the development of the Li-air battery.
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    10. 10
      Albertus, P.; Girishkumar, G.; McCloskey, B.; Sánchez-Carrera, R. S.; Kozinsky, B.; Christensen, J.; Luntz, A. C. Identifying Capacity Limitations in the Li/Oxygen Battery Using Experiments and Modeling. J. Electrochem. Soc. 2011, 158, A343– A351,  DOI: 10.1149/1.3527055
      [Crossref], [CAS], Google Scholar
      10
      Identifying Capacity Limitations in the Li/Oxygen Battery Using Experiments and Modeling
      Albertus, Paul; Girishkumar, G.; McCloskey, Bryan; Sanchez-Carrera, Roel S.; Kozinsky, Boris; Christensen, Jake; Luntz, A. C.
      Journal of the Electrochemical Society (2011), 158 (3), A343-A351CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      The Li/oxygen battery may achieve a high practical specific energy as its theor. specific energy is 11,400 Wh/kg Li assuming Li2O2 is the product. To help understand the physics of the Li/oxygen battery the first physics-based model that incorporates the major thermodn., transport, and kinetic processes is presented. A good match between porous-electrode expts. and simulations is obtained by using an empirical fit to the resistance of the discharge products (which include carbonates and oxides when using carbonate solvents) as a function of thickness that is obtained from flat-electrode expts. The expts. and model indicate that the discharge products are electronically resistive, limiting their thickness to tens of nanometers and their vol. fraction in one of the discharged porous electrodes to a few percent. Flat-electrode expts., where pore clogging is impossible, show passivation similar to porous-electrode expts. and allow to conclude that elec. passivation is the dominant capacity-limiting mechanism in the cells. Although in carbonate solvents Li2O2 is not the dominant discharge product, it is argued that the implications of this model, (i.e., elec. passivation by the discharge products limits the capacity) also apply if Li2O2 is the discharge product, as it is an intrinsic electronic insulator.
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    11. 11
      Franco, A. A.; Xue, K.-H. Carbon-Based Electrodes for Lithium Air Batteries: Scientific and Technological Challenges from a Modeling Perspective. ECS J. Solid State Sci. Technol. 2013, 2, M3084– M3100,  DOI: 10.1149/2.012310jss
      [Crossref], [CAS], Google Scholar
      11
      Carbon-based electrodes for lithium air batteries: scientific and technological challenges from a modeling perspective
      Franco, Alejandro A.; Xue, Kan-Hao
      ECS Journal of Solid State Science and Technology (2013), 2 (10), M3084-M3100CODEN: EJSSBG; ISSN:2162-8769. (Electrochemical Society)
      A review. The carbon-based pos. electrode of Lithium Air Batteries (LABs) is the component where the major competitive mechanisms occur, such as the electrochem. reactions leading to the formation and decompn. of multiple types of lithium oxides, lithium ion and electronic transport as well as oxygen transport. Through a multiscale viewpoint, this review discusses available models describing LAB carbon-based electrodes from the atomistic to continuum approaches. Relevance of those approaches vs. exptl. data as well as the remaining scientific and technol. challenges of these technologies are analyzed. Finally, this review briefly introduces a new theory aiming at studying the impact of the pos. electrode carbon structure onto the cyclability of LABs.
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    12. 12
      Xue, K.-H.; Nguyen, T.-K.; Franco, A. A. Impact of the Cathode Microstructure on the Discharge Performance of Lithium Air Batteries: A Multiscale Model. J. Electrochem. Soc. 2014, 161, E3028– E3035,  DOI: 10.1149/2.002408jes
      [Crossref], [CAS], Google Scholar
      12
      Impact of the Cathode Microstructure on the Discharge Performance of Lithium Air Batteries: A Multiscale Model
      Xue, Kan-Hao; Nguyen, Trong-Khoa; Franco, Alejandro A.
      Journal of the Electrochemical Society (2014), 161 (8), E3028-E3035CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      A multiscale model of lithium air batteries considering cathode pore size distribution is proposed, where the morphol. of the discharge product, Li2O2, is assumed to be thin films covering the surface of the pores. In the model, active surface area degrades during discharge because of three reasons. First, the effective radius of pores decreases due to Li2O2 coverage. Secondly, small pores may be fully choked. Thirdly, thick Li2O2 film may block the electron tunneling process, rendering the surface inactive. Simulation results reveal that the end of discharge in cells made of Super P and Ketjen Black carbons is caused by unavailable surface area near the air inlet, rather than the full choking of pores. Larger discharge capacity is found in the Ketjen Black cell because its high sp. surface area leads to slower Li2O2 thickness growth rate. This tunneling-limited model is compared with a linear resistance model where the Li2O2 thin film resistance is assumed to be proportional to its thickness. Different shapes of discharge curves were discovered: the former has a long discharge plateau followed by a sudden drop of cell voltage, while the latter shows a gradual decrease of cell voltage. These results are discussed in relation to the exptl. knowledge.
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    13. 13
      Liu, J.; Rahimian, S. K.; Monroe, C. W. Capacity-Limiting Mechanisms in Li/O2 Batteries. Phys. Chem. Chem. Phys. 2016, 18, 22840– 22851,  DOI: 10.1039/C6CP04055A
      [Crossref], [PubMed], [CAS], Google Scholar
      13
      Capacity-limiting mechanisms in Li/O2 batteries
      Liu, Jing; Khaleghi Rahimian, Saeed; Monroe, Charles W.
      Physical Chemistry Chemical Physics (2016), 18 (33), 22840-22851CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A continuum model of an aprotic lithium/oxygen battery is validated against exptl. first-discharge data and used to examine how the apparent cell capacity is affected by macroscopic multicomponent mass transfer, interfacial kinetics, and electronic conduction or tunneling through the discharge product. The model accounts for the three-phase nature of the pos. electrode in detail, including an explicit discharge-product layer whose properties and vol. distribution generally depend on the local discharge depth. Several hypothetical pos.-electrode reaction mechanisms involving different product morphologies and electron-transfer sites are explored within the theor. framework. To match exptl. discharge-voltage vs. capacity and capacity vs. discharge-current trends qual., the discharge-product layer must be assumed to have electronic resistivity several orders of magnitude lower than typical insulators, supporting the notion that the presence of lithium peroxide does not wholly prevent electrons from reaching dissolved reactants. The discharge product also appears to allow charge transport over length scales longer than electron tunneling permits. sudden death of voltage in lithium/oxygen cells is explained by macroscopic oxygen-diffusion limitations in the pos. electrode at high rates, and by pore clogging assocd. with discharge-product formation at low rates.
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    14. 14
      Bardenhagen, I.; Yezerska, O.; Augustin, M.; Fenske, D.; Wittstock, A.; Bäumer, M. In Situ Investigation of Pore Clogging during Discharge of a Li/O2 Battery by Electrochemical Impedance Spectroscopy. J. Power Sources 2015, 278, 255– 264,  DOI: 10.1016/j.jpowsour.2014.12.076
      [Crossref], [CAS], Google Scholar
      14
      In situ investigation of pore clogging during discharge of a Li/O2 battery by electrochemical impedance spectroscopy
      Bardenhagen, Ingo; Yezerska, Olga; Augustin, Matthias; Fenske, Daniela; Wittstock, Arne; Baeumer, Marcus
      Journal of Power Sources (2015), 278 (), 255-264CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      The behavior of three gas diffusion electrodes (GDE) with macro- and mesopores is investigated by in situ electrochem. impedance spectroscopy (EIS) in the Li/O2 battery system while discharging. Using a three electrode setup the current response from the anode (Li metal) and cathode (GDE) can be sepd. and the changes of the electrochem. processes at the GDE during discharge can be obsd., exclusively. Up to four processes are identified with different time consts. which is assigned to the lithium ion migration through a surface layer, the charge-transfer from the carbon surface to the mol. oxygen, the lithium ion and oxygen diffusion towards the cathode surface and, in case of the mesoporous materials, the lithium ion movement inside the pores, along the pore axis. The latter finding reflects that pore clogging of such is a limiting factor for the discharge of the Li/O2 battery. A large mesopore vol. as in the xerogel electrode, however, allows for a high storage capability and a long and const. oxygen redn. It is demonstrated that the three electrode EIS proves to be a powerful in situ diagnostic tool to det. the state and, hence, the reversibility of the reactions at the cathode.
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    15. 15
      Aklalouch, M.; Olivares-Marín, M.; Lee, R. C.; Palomino, P.; Enciso, E.; Tonti, D. Mass-Transport Control on the Discharge Mechanism in Li-O2 Batteries Using Carbon Cathodes with Varied Porosity. ChemSusChem 2015, 8, 3465– 3471,  DOI: 10.1002/cssc.201500719
      [Crossref], [PubMed], [CAS], Google Scholar
      15
      Mass-transport Control on the Discharge Mechanism in Li-O2 Batteries Using Carbon Cathodes with Varied Porosity
      Aklalouch, Mohamed; Olivares-Marin, Mara; Lee, Rung-Chuan; Palomino, Pablo; Enciso, Eduardo; Tonti, Dino
      ChemSusChem (2015), 8 (20), 3465-3471CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      By comparing carbon electrodes with varying porosity in Li-O2 cells, we show that the effect of electrolyte stirring at a given c.d. can result in a change from 2D to 3D growth of discharged deposits. The change of morphol. is evident using electron microscopy and by analyzing electrode pore size distribution with respect to discharge capacity. As a consequence, carbon electrodes with different textural properties exhibit different capacity enhancements in stirred-electrolyte cells. We demonstrate that mass transport can directly control the discharge mechanism, similar to the electrolyte compn. and c.d., which have already been recognized as detg. factors.
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    16. 16
      Ding, N.; Chien, S. W.; Hor, T. S. A.; Lum, R.; Zong, Y.; Liu, Z. Influence of Carbon Pore Size on the Discharge Capacity of Li-O2 Batteries. J. Mater. Chem. A 2014, 2, 12433– 12441,  DOI: 10.1039/C4TA01745E
      [Crossref], [CAS], Google Scholar
      16
      Influence of carbon pore size on the discharge capacity of Li-O2 batteries
      Ding, Ning; Chien, Sheau Wei; Hor, T. S. Andy; Lum, Regina; Zong, Yun; Liu, Zhaolin
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2014), 2 (31), 12433-12441CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Porous carbon materials play key roles in rechargeable Li-O2 batteries as oxygen diffusion media and sites for reversible electrode reactions. Despite tremendous efforts in the synthesis of various porous carbon materials, the effect of carbon materials on cell capacity remains unclear. Based on the study of eight different carbon electrode materials with various pore sizes and pore vols. in Li-O2 batteries, it was found that the initial discharge capacity was hardly affected by the surface area or pore vol. Instead, it was directly correlated with the pore sizes. To further verify this finding, meso- and macro-porous carbon materials with pore sizes in the range of 20-100 nm were prepd. using spherical silica as a template. The results clearly showed that the cell capacity increases with the increase of pore size and eventually reached its max. at 7169 mA h g-1 at a pore size of 80 nm. A phys. model proposed to illustrate the effect of carbon pore size on cell capacity is the formation of a monolayer of Li2O2 with a thickness of 7.8 nm inside the carbon pores during the discharge process which limits the diffusion of incoming oxygen at smaller pore size (< 80 nm).
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    17. 17
      Kim, D. Y.; Kim, M.; Kim, D. W.; Suk, J.; Park, J. J.; Park, O. O.; Kang, Y. Graphene Paper with Controlled Pore Structure for High-Performance Cathodes in Li–O2 Batteries. Carbon N. Y. 2016, 100, 265– 272,  DOI: 10.1016/j.carbon.2016.01.013
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    18. 18
      Lin, Y.; Moitoso, B.; Martinez-Martinez, C.; Walsh, E. D.; Lacey, S. D.; Kim, J. W.; Dai, L.; Hu, L.; Connell, J. W. Ultrahigh-Capacity Lithium-Oxygen Batteries Enabled by Dry-Pressed Holey Graphene Air Cathodes. Nano Lett. 2017, 17, 3252– 3260,  DOI: 10.1021/acs.nanolett.7b00872
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      18
      Ultrahigh-Capacity Lithium-Oxygen Batteries Enabled by Dry-Pressed Holey Graphene Air Cathodes
      Lin, Yi; Moitoso, Brandon; Martinez-Martinez, Chalynette; Walsh, Evan D.; Lacey, Steven D.; Kim, Jae-Woo; Dai, Liming; Hu, Liangbing; Connell, John W.
      Nano Letters (2017), 17 (5), 3252-3260CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Lithium-oxygen (Li-O2) batteries have the highest theor. energy d. of all the Li-based energy storage systems, but many challenges prevent them from practical use. A major obstacle is the sluggish performance of the air cathode, where both oxygen redn. (discharge) and oxygen evolution (charge) reactions occur. Recently, there have been significant advances in the development of graphene-based air cathode materials with a large surface area and catalytically active for both oxygen redn. and evolution reactions, esp. with addnl. catalysts or dopants. However, most studies reported so far have examd. air cathodes with a limited areal mass loading rarely exceeding 1 mg/cm2. Despite the high gravimetric capacity values achieved, the actual (areal) capacities of those batteries were far from sufficient for practical applications. Here, we present the fabrication, performance, and mechanistic investigations of high-mass-loading (up to 10 mg/cm2) graphene-based air electrodes for high-performance Li-O2 batteries. Such air electrodes could be easily prepd. within minutes under solvent-free and binder-free conditions by compression-molding holey graphene materials because of their unique dry compressibility assocd. with in-plane holes on the graphene sheet. Li-O2 batteries with high air cathode mass loadings thus prepd. exhibited excellent gravimetric capacity as well as ultrahigh areal capacity (as high as ∼40 mAh/cm2). The batteries were also cycled at a high curtailing areal capacity (2 mAh/cm2) and showed a better cycling stability for ultrathick cathodes than their thinner counterparts. Detailed post-mortem analyses of the electrodes clearly revealed the battery failure mechanisms under both primary and secondary modes, arising from the oxygen diffusion blockage and the catalytic site deactivation, resp. These results strongly suggest that the dry-pressed holey graphene electrodes are a highly viable architectural platform for high-capacity, high-performance air cathodes in Li-O2 batteries of practical significance.
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    19. 19
      Yu, R.; Fan, W.; Guo, X.; Dong, S. Highly Ordered and Ultra-Long Carbon Nanotube Arrays as Air Cathodes for High-Energy-Efficiency Li-Oxygen Batteries. J. Power Sources 2016, 306, 402– 407,  DOI: 10.1016/j.jpowsour.2015.12.042
      [Crossref], [CAS], Google Scholar
      19
      Highly ordered and ultra-long carbon nanotube arrays as air cathodes for high-energy-efficiency Li-oxygen batteries
      Yu, Ruimin; Fan, Wugang; Guo, Xiangxin; Dong, Shaoming
      Journal of Power Sources (2016), 306 (), 402-407CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Carbonaceous air cathodes with rational architecture are vital for the nonaq. Li-O2 batteries to achieve large energy d., high energy efficiency and long cycle life. In this work, we report the cathodes made of highly ordered and vertically aligned carbon nanotubes grown on permeable Ta foil substrates (VACNTs-Ta) via thermal chem. vapor deposition. The VACNTs-Ta, composed of uniform carbon nanotubes with approx. 240 μm in superficial height, has the super large surface area. Meanwhile, the oriented carbon nanotubes provide extremely outstanding passageways for Li ions and oxygen species. Electrochem. tests of VACNTs-Ta air cathodes show enhancement in discharge capacity and cycle life compared to those made from short-range oriented and disordered carbon nanotubes. By further combining with the LiI redox mediator that is dissolved in the tetraethylene di-Me glycol based electrolytes, the batteries exhibit more than 200 cycles at the c.d. of 200 mA g-1 with a cut-off discharge capacity of 1000 mA h g-1, and their energy efficiencies increase from 50% to 82%. The results here demonstrate the importance of cathode construction for high-energy-efficiency and long-life Li-O2 batteries.
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    20. 20
      Aurbach, D.; McCloskey, B. D.; Nazar, L. F.; Bruce, P. G. Advances in Understanding Mechanisms Underpinning Lithium–Air Batteries. Nat. Energy 2016, 1, 16128,  DOI: 10.1038/nenergy.2016.128
      [Crossref], [CAS], Google Scholar
      20
      Advances in understanding mechanisms underpinning lithium-air batteries
      Aurbach, Doron; McCloskey, Bryan D.; Nazar, Linda F.; Bruce, Peter G.
      Nature Energy (2016), 1 (9), 16128CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
      A review. The rechargeable lithium-air battery has the highest theor. specific energy of any rechargeable battery and could transform energy storage if a practical device could be realized. At the fundamental level, little was known about the reactions and processes that take place in the battery, representing a significant barrier to progress. Here, we review recent advances in understanding the chem. and electrochem. that govern the operation of the lithium-air battery, esp. the reactions at the cathode. The mechanisms of O2 redn. to Li2O2 on discharge and the reverse process on charge are discussed in detail, as are their consequences for the rate and capacity of the battery. The various parasitic reactions involving the cathode and electrolyte during discharge and charge are also considered. We also provide views on understanding the stability of the cathode and electrolyte and examine design principles for better lithium-air batteries.
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    21. 21
      Abraham, K. M. Electrolyte-Directed Reactions of the Oxygen Electrode in Lithium-Air Batteries. J. Electrochem. Soc. 2014, 162, A3021– A3031,  DOI: 10.1149/2.0041502jes
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    22. 22
      Laoire, C. O.; Mukerjee, S.; Abraham, K. M.; Plichta, E. J.; Hendrickson, M. A. Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium–Air Battery. J. Phys. Chem. C 2010, 114, 9178– 9186,  DOI: 10.1021/jp102019y
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      22
      Influence of Nonaqueous Solvents on the Electrochemistry of Oxygen in the Rechargeable Lithium-Air Battery
      Laoire, Cormac O.; Mukerjee, Sanjeev; Abraham, K. M.; Plichta, Edward J.; Hendrickson, Mary A.
      Journal of Physical Chemistry C (2010), 114 (19), 9178-9186CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The influence of solvents on the O redn. reaction (ORR) in nonaq. electrolytes was studied for the mechanism of O electrode processes in a rechargeable Li-air battery. Using either Bu4NPF6 (TBAPF6) or LiPF6 electrolyte solns. in 4 different solvents, DMSO, MeCN, dimethoxyethane (DME), and tetraethylene glycol di-Me ether (TEGDME), possessing a range of donor nos. (DN), the solvent and the supporting electrolyte cations in the soln. act in concert to influence the nature of redn. products and their rechargeability. In solns. contg. TBA+, O2 redn. is a reversible 1-electron process involving the O2/O2- couple. However, in Li+-contg. electrolytes relevant to the Li-air battery, O2 redn. proceeds in a stepwise fashion to form O2-, O22-, and O2- as products. These reactions in the presence of Li+ are irreversible or quasi-reversible electrochem. processes, and the solvents have significant influence on the kinetics, and reversibility or lack thereof, of the different redn. products. The stabilization of the 1-electron redn. product, superoxide (O2-) in TBA+ solns. in all of the solvents examd. can be explained using Pearson's hard/soft acid base (HSAB) theory involving the formation of the TBA+---O2- complex. The HSAB theory coupled with the relative stabilities of the Li+-(solvent)n complexes existing in the different solvents also provide an explanation for the different O2 redn. products formed in Li+-conducting electrolyte solns. Reversible redn. of O2 to long-lived superoxide in a Li+-conducting electrolyte in DMSO was shown for the 1st time here. The results aid the selection of org. electrolyte solns. for use in rechargeable Li-air batteries.
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    23. 23
      Johnson, L.; Li, C.; Liu, Z.; Chen, Y.; Freunberger, S. A.; Ashok, P. C.; Praveen, B. B.; Dholakia, K.; Tarascon, J. M.; Bruce, P. G. The Role of LiO2 Solubility in O2 Reduction in Aprotic Solvents and Its Consequences for Li–O2 Batteries. Nat. Chem. 2014, 6, 1091– 1099,  DOI: 10.1038/nchem.2101
      [Crossref], [PubMed], [CAS], Google Scholar
      23
      The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li-O2 batteries
      Johnson, Lee; Li, Chunmei; Liu, Zheng; Chen, Yuhui; Freunberger, Stefan A.; Ashok, Praveen C.; Praveen, Bavishna B.; Dholakia, Kishan; Tarascon, Jean-Marie; Bruce, Peter G.
      Nature Chemistry (2014), 6 (12), 1091-1099CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      When lithium-oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 redn. in aprotic solvents is therefore essential to realizing their technol. potential. Two different models have been proposed for Li2O2 formation, involving either soln. or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 redn. across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 redn. through its effect on the soly. of LiO2, or, more precisely, the free energy of the reaction LiO2* .dblharw. Li(sol)+ + O2-(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-no. solvents are likely to lead to premature cell death, and that the future direction of research for lithium-oxygen batteries should focus on the search for new, stable, high-donor-no. electrolytes, because they can support higher capacities and can better sustain discharge.
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    24. 24
      Burke, C. M.; Pande, V.; Khetan, A.; Viswanathan, V.; Mccloskey, B. D. Enhancing Electrochemical Intermediate Solvation through Electrolyte Anion Selection to Increase Nonaqueous Li–O2 Battery Capacity. Proc. Natl. Acad., Sci. U. S. A. 2015, 112, 9293,  DOI: 10.1073/pnas.1505728112
      [Crossref], [PubMed], [CAS], Google Scholar
      24
      Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O2 battery capacity
      Burke, Colin M.; Pande, Vikram; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D.
      Proceedings of the National Academy of Sciences of the United States of America (2015), 112 (30), 9293-9298CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Among the beyond Li-ion battery chemistries, nonaq. Li-O2 batteries have the highest theor. specific energy and, as a result, have attracted significant research attention over the past decade. A crit. scientific challenge facing nonaq. Li-O2 batteries is the electronically insulating nature of the primary discharge product, Li peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance soly. to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochem. stability of the system, thereby deleteriously affecting battery rechargeability. The authors report that a significant enhancement (greater than 4-fold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte soln. Using 7Li NMR and modeling, this improvement is a result of enhanced Li+ stability in soln., which, in turn, induces soly. of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate soly. and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. The authors believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochem. systems (e.g., Li-S batteries) where improving intermediate stability in soln. could induce desired mechanisms of product formation.
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    25. 25
      Aetukuri, N. B.; McCloskey, B. D.; García, J. M.; Krupp, L. E.; Viswanathan, V.; Luntz, A. C. Solvating Additives Drive Solution-Mediated Electrochemistry and Enhance Toroid Growth in Non-Aqueous Li-O2 Batteries. Nat. Chem. 2015, 7, 50– 56,  DOI: 10.1038/nchem.2132
      [Crossref], [PubMed], [CAS], Google Scholar
      25
      Solvating additives drive solution-mediated electrochemistry and enhance toroid growth in non-aqueous Li-O2 batteries
      Aetukuri, Nagaphani B.; McCloskey, Bryan D.; Garcia, Jeannette M.; Krupp, Leslie E.; Viswanathan, Venkatasubramanian; Luntz, Alan C.
      Nature Chemistry (2015), 7 (1), 50-56CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      Given their high theor. specific energy, Li-O batteries have received enormous attention as possible alternatives to current state-of-the-art rechargeable Li-ion batteries. However, the max. discharge capacity in nonaq. Li-O batteries is limited to a small fraction of its theor. value due to the build-up of insulating Li peroxide (Li2O2), the battery's primary discharge product. The discharge capacity can be increased if Li2O2 forms as large toroidal particles rather than as a thin conformal layer. Here, trace amts. of electrolyte additives, such as H2O, enhance the formation of Li2O2 toroids and result in significant improvements in capacity. The exptl. observations and a growth model show that the solvating properties of the additives prompt a soln.-based mechanism that is responsible for the growth of Li2O2 toroids. The authors present a general formalism describing an additive's tendency to trigger the soln. process, providing a rational design route for electrolytes that afford larger Li-O battery capacities.
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    26. 26
      Liu, T.; Frith, J. T.; Kim, G.; Kerber, R. N.; Dubouis, N.; Shao, Y.; Liu, Z.; Magusin, P. C. M. M.; Casford, M. T. L.; Garcia-Araez, N. The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries. J. Am. Chem. Soc. 2018, 140, 1428– 1437,  DOI: 10.1021/jacs.7b11007
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      26
      The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries
      Liu, Tao; Frith, James T.; Kim, Gunwoo; Kerber, Rachel N.; Dubouis, Nicolas; Shao, Yuanlong; Liu, Zigeng; Magusin, Pieter C. M. M.; Casford, Michael T. L.; Garcia-Araez, Nuria; Grey, Clare P.
      Journal of the American Chemical Society (2018), 140 (4), 1428-1437CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The parasitic reactions assocd. with reduced oxygen species and the difficulty in achieving the high theor. capacity have been major issues plaguing development of practical nonaq. Li-O2 batteries. We hereby address the above issues by exploring the synergistic effect of 2,5-di-tert-butyl-1,4-benzoquinone and H2O on the oxygen chem. in a nonaq. Li-O2 battery. Water stabilizes the quinone monoanion and dianion, shifting the redn. potentials of the quinone and monoanion to more pos. values (vs Li/Li+). When water and the quinone are used together in a (largely) nonaq. Li-O2 battery, the cell discharge operates via a two-electron oxygen redn. reaction to form Li2O2, with the battery discharge voltage, rate, and capacity all being considerably increased and fewer side reactions being detected. Li2O2 crystals can grow up to 30 μm, more than an order of magnitude larger than cases with the quinone alone or without any additives, suggesting that water is essential to promoting a soln. dominated process with the quinone on discharging. The catalytic redn. of O2 by the quinone monoanion is predominantly responsible for the attractive features mentioned above. Water stabilizes the quinone monoanion via hydrogen-bond formation and by coordination of the Li+ ions, and it also helps increase the solvation, concn., lifetime, and diffusion length of reduced oxygen species that dictate the discharge voltage, rate, and capacity of the battery. When a redox mediator is also used to aid the charging process, a high-power, high energy d., rechargeable Li-O2 battery is obtained.
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    27. 27
      Lacey, M. J.; Frith, J. T.; Owen, J. R. A Redox Shuttle to Facilitate Oxygen Reduction in the Lithium Air Battery. Electrochem. Commun. 2013, 26, 74– 76,  DOI: 10.1016/j.elecom.2012.10.009
      [Crossref], [CAS], Google Scholar
      27
      A redox shuttle to facilitate oxygen reduction in the lithium air battery
      Lacey, Matthew J.; Frith, James T.; Owen, John R.
      Electrochemistry Communications (2013), 26 (), 74-76CODEN: ECCMF9; ISSN:1388-2481. (Elsevier B.V.)
      A novel design of the non-aq. lithium air cell is presented with a demonstration of a new reaction concept, involving a sol. redox shuttle to catalyze oxygen redn. In principle, this can relieve the requirement for fast diffusion of mol. oxygen from the air interface to the pos. electrode. To demonstrate this concept, Et viologen ditriflate was dissolved in BMPTFSI, reduced at a carbon electrode and regenerated by aspiration with oxygen. Useful shuttle behavior, confirmed by several redn.-oxidn. cycles, was obsd. in the case where the electrolyte contained at least 0.3 M lithium salt. The beneficial effect of the salt was attributed to its crit. role in converting superoxide, which would otherwise destroy the shuttle, into the more desirable product of oxygen redn., lithium peroxide.
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    28. 28
      Lim, H. D.; Lee, B.; Zheng, Y.; Hong, J.; Kim, J.; Gwon, H.; Ko, Y.; Lee, M.; Cho, K.; Kang, K. Rational Design of Redox Mediators for Advanced Li-O2 Batteries. Nat. Energy 2016, 1, 16066,  DOI: 10.1038/nenergy.2016.66
      [Crossref], [CAS], Google Scholar
      28
      Rational design of redox mediators for advanced Li-O2 batteries
      Lim, Hee-Dae; Lee, Byungju; Zheng, Yongping; Hong, Jihyun; Kim, Jinsoo; Gwon, Hyeokjo; Ko, Youngmin; Lee, Minah; Cho, Kyeongjae; Kang, Kisuk
      Nature Energy (2016), 1 (6), 16066CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
      The discovery of effective catalysts is an important step towards achieving Li-O2 batteries with long cycle life and high round-trip efficiency. Sol.-type catalysts or redox mediators (RMs) possess great advantages over conventional solid catalysts, generally exhibiting much higher efficiency. Here, we select a series of org. RM candidates as a model system to identify the key descriptor in detg. the catalytic activities and stabilities in Li-O2 cells. It is revealed that the level of ionization energies, readily available parameters from a database of the mols., can serve such a role when comparing with the formation energy of Li2O2 and the HOMO energy of the electrolyte. It is demonstrated that they are crit. in reducing the overpotential and improving the stability of Li-O2 cells, resp. Accordingly, we propose a general principle for designing feasible catalysts and report a RM, dimethylphenazine, with a remarkably low overpotential and high stability.
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    29. 29
      Gao, X.; Chen, Y.; Johnson, L.; Bruce, P. G. Promoting Solution Phase Discharge in Li-O2 Batteries Containing Weakly Solvating Electrolyte Solutions. Nat. Mater. 2016, 15, 882– 888,  DOI: 10.1038/nmat4629
      [Crossref], [PubMed], [CAS], Google Scholar
      29
      Promoting solution phase discharge in Li-O2 batteries containing weakly solvating electrolyte solutions
      Gao, Xiangwen; Chen, Yuhui; Johnson, Lee; Bruce, Peter G.
      Nature Materials (2016), 15 (8), 882-888CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      On discharge, the Li-O2 battery can form a Li2O2 film on the cathode surface, leading to low capacities, low rates and early cell deactivation, or it can form Li2O2 particles in soln., leading to high capacities at relatively high rates and avoiding early cell deactivation. Achieving discharge in soln. is important and may be encouraged by the use of high donor or acceptor no. solvents or salts that dissolve the LiO2 intermediate involved in the formation of Li2O2. However, the characteristics that make high donor or acceptor no. solvents good (for example, high polarity) result in them being unstable towards LiO2 or Li2O2. Here we demonstrate that introduction of the additive 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) promotes soln. phase formation of Li2O2 in low-polarity and weakly solvating electrolyte solns. Importantly, it does so while simultaneously suppressing direct redn. to Li2O2 on the cathode surface, which would otherwise lead to Li2O2 film growth and premature cell death. It also halves the overpotential during discharge, increases the capacity 80- to 100-fold and enables rates >1 mA cmareal-2 for cathodes with capacities of >4 mAh cmareal-2. The DBBQ additive operates by a new mechanism that avoids the reactive LiO2 intermediate in soln.
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    30. 30
      Li, Y.; Zhang, Z.; Duan, D.; Sun, Y.; Wei, G.; Hao, X.; Liu, S.; Han, Y.; Meng, W. The Correlation of the Properties of Pyrrolidinium-Based Ionic Liquid Electrolytes with the Discharge–Charge Performances of Rechargeable Li–O2 Batteries. J. Power Sources 2016, 329, 207– 215,  DOI: 10.1016/j.jpowsour.2016.08.077
      [Crossref], [CAS], Google Scholar
      30
      The correlation of the properties of pyrrolidinium-based ionic liquid electrolytes with the discharge-charge performances of rechargeable Li-O2 batteries
      Li, Yu; Zhang, Zhonglin; Duan, Donghong; Sun, Yanbo; Wei, Guoqiang; Hao, Xiaogang; Liu, Shibin; Han, Yunxia; Meng, Weijuan
      Journal of Power Sources (2016), 329 (), 207-215CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Pyrrolidinium-based ionic liqs. (ILs), such as PYR13TFSI, PYR14TFSI, and PYR1(2O1)TFSI, exhibit high thermal and electrochem. stability with wide electrochem. windows as electrolytes for application to rechargeable Li-O2 batteries. Here, several fundamental properties of 3 ILs are measured: the ionic cond., O soly., and O diffusion coeff. The O electro-redn. kinetics is characterized using cyclic voltammetry. The performances of Li-O2 batteries with these IL electrolytes are also studied using electrochem. impedance spectroscopy and galvanostatic discharge-charge tests. The results demonstrate that the PYR1(2O1)TFSI electrolyte battery has a higher 1st-discharge voltage than the PYR13TFSI electrolyte and PYR14TFSI electrolyte batteries. Both PYR13TFSI- and PYR1(2O1)TFSI-based batteries exhibit higher 1st-discharge capacities and better cycling stabilities than the PYR14TFSI-based battery for 30 cycles. A theor. anal. of the exptl. results shows that the diffusion coeff. and soly. of O in the electrolyte remarkably affect the discharge capacity and cycling stability of the batteries. Particularly, the O diffusion coeff. of the IL electrolyte can effectively facilitate the electrochem. O electro-redn. reaction and O concn. distribution in the catalyst layers of air electrodes. The O diffusion coeff. and O soly. improvements of IL electrolytes can enhance the discharge-charge performances of Li-O2 batteries.
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    31. 31
      Wu, C.; Li, T.; Liao, C.; Xu, Q.; Cao, Y.; Li, L.; Yang, J. Enhanced Electrochemical Performance of Non-Aqueous Li–O2 Batteries with Triethylene Glycol Dimethyl Ether-Based Electrolyte. J. Electrochem. Soc. 2017, 164, A1321– A1327,  DOI: 10.1149/2.0251707jes
      [Crossref], [CAS], Google Scholar
      31
      Enhanced Electrochemical Performance of Non-Aqueous Li-O2 Batteries with Triethylene Glycol Dimethyl Ether-Based Electrolyte
      Wu, Chaolumen; Li, Taoran; Liao, Chenbo; Xu, Qingkai; Cao, Yuancheng; Li, Lei; Yang, Jun
      Journal of the Electrochemical Society (2017), 164 (6), A1321-A1327CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      Triethylene glycol di-Me ether (G3) is evaluated as an electrolyte solvent for non-aq. lithium-oxygen (Li-O2) batteries. A liq. electrolyte of 1 M LiTFSI in G3 shows lower viscosity, higher oxygen soly. and diffusion, higher ionic cond. and lithium ionic transference no. compared to the conventional liq. electrolyte of 1 M LiTFSI in tetraethylene glycol di-Me ether (G4). Then the Li-O2 battery using the G3-based electrolyte shows better cycling stability and higher rate capability compared to the battery using the G4-based electrolyte. At a higher c.d. of 2.5 A gcarbon-1, the discharge capacity of the battery using the G3-based electrolyte is about 1472 mAh gcarbon-1, which is about four times higher than that of the battery using the G4-based electrolyte. At c.d. of 1 A gcarbon-1 with a fixed capacity of 1000 mAh gcarbon-1, the battery using the G3-based electrolyte can be operated stably for 80 cycles, while only 20 cycles are achieved by using the G4-based electrolyte. Therefore, the G3-based electrolyte could be a proper alternative electrolyte to the conventional G4-based electrolyte for the development of Li-O2 batteries.
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    32. 32
      Cui, Y.; Wen, Z.; Liang, X.; Lu, Y.; Jin, J.; Wu, M.; Wu, X. A Tubular Polypyrrole Based Air Electrode with Improved O2 Diffusivity for Li-O2 Batteries. Energy Environ. Sci. 2012, 5, 7893– 7897,  DOI: 10.1039/c2ee21638h
      [Crossref], [CAS], Google Scholar
      32
      A tubular polypyrrole based air electrode with improved O2 diffusivity for Li-O2 batteries
      Cui, Yanming; Wen, Zhaoyin; Liang, Xiao; Lu, Yan; Jin, Jun; Wu, Meifen; Wu, Xiangwei
      Energy & Environmental Science (2012), 5 (7), 7893-7897CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      A highly reversible air electrode was designed based on the hydrophilic nano-PPy tubes with abundant gas diffusion channels and reaction space which greatly improved the cell capacity, cycling stability and esp. the rate performance of the lithium-oxygen batteries.
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    33. 33
      Li, X.; Huang, J.; Faghri, A. Modeling Study of a Li-O2 Battery with an Active Cathode. Energy 2015, 81, 489– 500,  DOI: 10.1016/j.energy.2014.12.062
      [Crossref], [CAS], Google Scholar
      33
      Modeling study of a Li-O2 battery with an active cathode
      Li, Xianglin; Huang, Jing; Faghri, Amir
      Energy (Oxford, United Kingdom) (2015), 81 (), 489-500CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      In this study, a new org. lithium oxygen (Li-O2) battery structure is proposed to enhance battery capacity. The electrolyte is forced to recirculate through the cathode and then satd. with oxygen in a tank external to the battery. The forced convection enhances oxygen transport and alleviates the problem of electrode blockage during discharge. A two dimensional, transient, non-isothermal simulation model is developed to study the heat and mass transfer within the battery and validate the proposed design. Results show that this novel active cathode design improves the battery capacity at all discharge current densities. The capacity of the Li-O2 battery is increased by 15.5 times (from 12.2 mAh g-1 to 201 mAh g-1) at the discharge current of 2.0 mA cm-2 when a conventional passive electrode is replaced by the newly designed active electrode. Furthermore, a cathode with non-uniform porosity is suggested and simulation results show that it can reach a higher discharge capacity without decreasing its power d. Detailed mass transport processes in the battery are also studied.
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    34. 34
      Wang, F.; Xu, Y. H.; Luo, Z. K.; Pang, Y.; Wu, Q. X.; Liang, C. S.; Chen, J.; Liu, D.; Zhang, X. H. A Dual Pore Carbon Aerogel Based Air Cathode for a Highly Rechargeable Lithium-Air Battery. J. Power Sources 2014, 272, 1061– 1071,  DOI: 10.1016/j.jpowsour.2014.08.126
      [Crossref], [CAS], Google Scholar
      34
      A dual pore carbon aerogel-based air cathode for a highly rechargeable lithium-air battery
      Wang, Fang; Xu, Yang-Hai; Luo, Zhong-Kuan; Pang, Yan; Wu, Qi-Xing; Liang, Chun-Sheng; Chen, Jing; Liu, Dong; Zhang, Xiang-hua
      Journal of Power Sources (2014), 272 (), 1061-1071CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Cathode structure plays a vital role in Li-air battery for that it can provide space for discharged products accommodation and free path for O, e- and Li+ transport. However, pore blockage, cathode passivation and degrdn. all result in low discharge rates and poor cycling capability. To get rid of these problems, a novel highly conductive dual pore C aerogel based air cathode is fabricated to construct a Li-air battery, which exhibits 18 to 525 cycles in the LiTFSI/sulfolane electrolyte at a c.d. varying from 1.00 mA cm-2 to 0.05 mA cm-2, accompanied by a high energy efficiency of 78.32%. The authors postulate that the essence lies in that the as-prepd. air cathode inventively create a suitable tri-phase boundary reaction zone, facilitating O and Li+ diffusion in 2 independent pore channels, thus realizing a relative higher discharge rate capability, lower pore blockage and cathode passivation. Further, pore structure, C loading, rate capability, discharge depth and the air's effect are exploited and coordinated, targeting for a high power and reversible Li-air battery. Such nanoporous C aerogel air cathode of novel dual pore structure and material design is expected to be an attractive alternative for Li-air batteries and other Li based batteries.
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    35. 35
      Forse, A. C.; Griffin, J. M.; Merlet, C.; Carretero-Gonzalez, J.; Raji, A.-R. O.; Trease, N. M.; Grey, C. P. Direct Observation of Ion Dynamics in Supercapacitor Electrodes Using in Situ Diffusion NMR Spectroscopy. Nat. Energy 2017, 2, 16216,  DOI: 10.1038/nenergy.2016.216
      [Crossref], [CAS], Google Scholar
      35
      Direct observation of ion dynamics in supercapacitor electrodes using in situ diffusion NMR spectroscopy
      Forse, Alexander C.; Griffin, John M.; Merlet, Celine; Carretero-Gonzalez, Javier; Raji, Abdul-Rahman O.; Trease, Nicole M.; Grey, Clare P.
      Nature Energy (2017), 2 (2), 16216/1-16216/7CODEN: NEANFD; ISSN:2058-7546. (Nature Publishing Group)
      Ionic transport inside porous carbon electrodes underpins the storage of energy in supercapacitors and the rate at which they can charge and discharge, yet few studies have elucidated the materials properties that influence ion dynamics. Here we use in situ pulsed field gradient NMR spectroscopy to measure ionic diffusion in supercapacitors directly. We find that confinement in the nanoporous electrode structures decreases the effective self-diffusion coeffs. of ions by over two orders of magnitude compared with neat electrolyte, and in-pore diffusion is modulated by changes in ion populations at the electrode/electrolyte interface during charging. Electrolyte concn. and carbon pore size distributions also affect in-pore diffusion and the movement of ions in and out of the nanopores. In light of our findings we propose that controlling the charging mechanism may allow the tuning of the energy and power performances of supercapacitors for a range of different applications.
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    36. 36
      Engelke, S.; Marbella, L. E.; Trease, N. M.; De Volder, M.; Grey, C. P. Three-Dimensional Pulsed Field Gradient NMR Measurements of Self-Diffusion in Anisotropic Materials for Energy Storage Applications. Phys. Chem. Chem. Phys. 2019, 21, 4538– 4546,  DOI: 10.1039/C8CP07776B
      [Crossref], [PubMed], [CAS], Google Scholar
      36
      Three-dimensional pulsed field gradient NMR measurements of self-diffusion in anisotropic materials for energy storage applications
      Engelke, S.; Marbella, L. E.; Trease, N. M.; De Volder, M.; Grey, C. P.
      Physical Chemistry Chemical Physics (2019), 21 (8), 4538-4546CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Anisotropic battery electrodes that allow enhanced diffusion through the thickness of the electrode can be engineered to improve the rate performance, but direct measurement of 3D diffusion in this pore structure is extremely challenging. To address this, we used 1H and 7Li pulsed field gradient (PFG) NMR to measure anisotropic diffusion in a model porous silicon substrate. We show that NMR spectroscopy can resolve solvent mols. and ions (here, in H2O, DMSO, and the battery electrolyte LIPF6:DC:EMC) in and outside of the pores of the Si substrate, allowing the diffusion coeffs. of the ion/mols. in the two components to be individually detd. Exchange between ions/mols. inside and outside of the pores is obsd. with 1H 2D exchange spectroscopy (EXSY). The pore dimensions can extd. from the diffusivity of the in-pore component and the results are in reasonable agreement with the pore dimensions measured with electron microscopy. Better agreement is obtained for pore diams.; for pore length measurements, exchange between the in-pore and ex-pore solvents should be accounted for. These results suggest that PFG-NMR can serve as a non-destructive characterization method for both in situ and ex situ analyses of materials ranging from complex battery and supercapacitor electrodes to catalyst supports and tissue scaffolds.
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    37. 37
      Stallmach, F.; Kärger, J.; Krause, C.; Jeschke, M.; Oberhagemann, U. Evidence of Anisotropic Self-Diffusion of Guest Molecules in Nanoporous Materials of MCM-41 Type. J. Am. Chem. Soc. 2000, 122, 9237– 9242,  DOI: 10.1021/ja001106x
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      37
      Evidence of Anisotropic Self-Diffusion of Guest Molecules in Nanoporous Materials of MCM-41 Type
      Stallmach, Frank; Kaerger, Joerg; Krause, Cordula; Jeschke, Markus; Oberhagemann, Uwe
      Journal of the American Chemical Society (2000), 122 (38), 9237-9242CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The pore architecture of MCM-41 was investigated by pulsed field gradient NMR (PFG NMR) self-diffusion measurements of adsorbed water. Over diffusion length scales which exceed the radius of the one-dimensional channels of the MCM-41 by 2 orders of magnitude but which are smaller than the size of the individual MCM-41 particles, the mol. propagation of the guest mols. was found to be highly anisotropic. The PFG NMR exptl. data are best represented by an axisym. diffusion tensor rather than by pure one-dimensional diffusion along the channels. This suggests that the pore walls of the one-dimensional channels are permeable for water or that over the probed diffusion length the channels are disordered and bent. Both interpretations provide information on the pore structure of the nanoporous material which is not available from X-ray diffraction data.
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    38. 38
      Kondrashova, D.; Lauerer, A.; Mehlhorn, D.; Jobic, H.; Feldhoff, A.; Thommes, M.; Chakraborty, D.; Gommes, C.; Zecevic, J.; De Jongh, P. Scale-Dependent Diffusion Anisotropy in Nanoporous Silicon. Sci. Rep. 2017, 7, 1– 10,  DOI: 10.1038/srep40207
      [Crossref], [PubMed], [CAS], Google Scholar
      38
      Phase transitions in disordered mesoporous solids
      Schneider, Daniel; Kondrashova, Daria; Valiullin, Rustem
      Scientific Reports (2017), 7 (1), 1-13CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)
      Fluids confined in mesoporous solids exhibit a wide range of phys. behavior including rich phase equil. While a notable progress in their understanding has been achieved for fluids in materials with geometrically ordered pore systems, mesoporous solids with complex pore geometries still remain a topic of active research. In this work we study phase transitions occurring in statistically disordered linear chains of pores with different pore sizes. By considering, quite generally, two phase change mechanisms, nucleation and phase growth, occurring simultaneously we obtain the boundary transitions and the scanning curves resulting upon reversing the sign of the evolution of the chem. potential at different points along the main transition branches. The results obtained are found to reproduces the key exptl. observations, including the emergence of hysteresis and the scanning behavior. By deriving the serial pore model isotherm we suggest a robust framework for reliable structural anal. of disordered mesoporous solids.
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    39. 39
      Torayev, A.; Rucci, A.; Magusin, P. C. M. M.; Demortière, A.; De Andrade, V.; Grey, C. P.; Merlet, C.; Franco, A. A. Stochasticity of Pores Interconnectivity in Li-O2 Batteries and Its Impact on the Variations in Electrochemical Performance. J. Phys. Chem. Lett. 2018, 9, 791– 797,  DOI: 10.1021/acs.jpclett.7b03315
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      39
      Stochasticity of Pores Interconnectivity in Li-O2 Batteries and its Impact on the Variations in Electrochemical Performance
      Torayev, Amangeldi; Rucci, Alexis; Magusin, Pieter C. M. M.; Demortiere, Arnaud; De Andrade, Vincent; Grey, Clare P.; Merlet, Celine; Franco, Alejandro A.
      Journal of Physical Chemistry Letters (2018), 9 (4), 791-797CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      While large dispersions in electrochem. performance have been reported for lithium oxygen batteries in the literature, they have not been investigated in any depth. The variability in the results is often assumed to arise from differences in cell design, electrode structure, handling and cell prepn. at different times. An accurate theor. framework turns out to be needed to get a better insight into the mechanisms underneath and to interpret exptl. results. Here, we develop and use a pore network model to simulate the electrochem. performance of three-dimensionally resolved lithium-oxygen cathode mesostructures obtained from TXM nanocomputed tomog. We apply this model to the 3D reconstructed object of a Super P carbon electrode and calc. discharge curves, using identical conditions, for four different zones in the electrode and their reversed configurations. The resulting galvanostatic discharge curves show some dispersion, (both in terms of capacity and overpotential) which we attribute to the way pores are connected with each other. Based on these results, we propose that the stochastic nature of pore interconnectivity and the microscopic arrangement of pores can lead, at least partially, to the variations in electrochem. results obsd. exptl.
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    40. 40
      Torayev, A.; Magusin, P. C. M. M.; Grey, C. P.; Merlet, C.; Franco, A. A. Importance of Incorporating Explicit 3D-Resolved Electrode Mesostructures in Li–O2 Battery Models. ACS Appl. Energy Mater. 2018, 1, 6433– 6441,  DOI: 10.1021/acsaem.8b01392
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    41. 41
      Stejskal, E. O.; Tanner, J. E. Spin Diffusion Measurements: Spin Echoes in the Presence of a Time-Dependent Field Gradient. J. Chem. Phys. 1965, 42, 288– 292,  DOI: 10.1063/1.1695690
      [Crossref], [CAS], Google Scholar
      41
      Spin diffusion measurements: spin echoes in the presence of a time-dependent field gradient
      Stejskal, E. O.; Tanner, J. E.
      Journal of Chemical Physics (1965), 42 (1), 288-92CODEN: JCPSA6; ISSN:0021-9606.
      A derivation is given of the effect of a time-dependent magnetic field gradient on the spin-echo expt., particularly in the presence of spin diffusion. There are several reasons for preferring certain kinds of time-dependent magnetic field gradients to the more usual steady gradient. If the gradient is reduced during the radio-frequency pulses, H1 need not be particularly large; if the gradient is small at the time of the echo, the echo will be broad and its amplitude easy to measure. Both of these relaxations of restrictions on the measurement of diffusion coeffs. by the spin-echo technique serve to extend its range of applicability. A pulsed gradient can be recommended when it is crit. to define the precise time period over which diffusion is being measured. The theoretical expression derived was verified exptl. for several choices of time-dependent magnetic field gradient. An app. is described suitable for the production of pulsed gradients with amplitudes as large as 100 gauss cm. The diffusion coeff. of dry glycerol at 26° ± 1° is (2.5 ± 0.2) × 10-3 cm.2/sec., a value smaller than can ordinarily be measured by the steady gradient method.
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    42. 42
      Price, W. S. NMR Studies of Translational Motion; Cambridge University Press: Cambridge, 2009,  DOI: 10.1017/CBO9780511770487 .
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    43. 43
      Chung, D.-W.; Ebner, M.; Ely, D. R.; Wood, V.; Edwin García, R. Validity of the Bruggeman Relation for Porous Electrodes. Modell. Simul. Mater. Sci. Eng. 2013, 21, 074009  DOI: 10.1088/0965-0393/21/7/074009
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    44. 44
      De Andrade, V.; Deriy, A.; Wojcik, M. J.; Gürsoy, D.; Shu, D.; Fezzaa, K.; De Carlo, F. Nanoscale 3D Imaging at the Advanced Photon Source. SPIE Newsroom 2016, 006461  DOI: 10.1117/2.1201604.006461
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    45. 45
      Su, Z.; De Andrade, V.; Cretu, S.; Yin, Y.; Wojcik, M. J.; Franco, A. A.; Demortière, A. X-Ray Nanocomputed Tomography in Zernike Phase Contrast for Studying 3D Morphology of Li–O2 Battery Electrode. ACS Appl. Energy Mater. 2020, 3, 4093– 4102,  DOI: 10.1021/acsaem.9b02236
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      45
      X-ray Nanocomputed Tomography in Zernike Phase Contrast for Studying 3D Morphology of Li-O2 Battery Electrode
      Su, Zeliang; De Andrade, Vincent; Cretu, Sorina; Yin, Yinghui; Wojcik, Michael J.; Franco, Alejandro A.; Demortiere, Arnaud
      ACS Applied Energy Materials (2020), 3 (5), 4093-4102CODEN: AAEMCQ; ISSN:2574-0962. (American Chemical Society)
      The lithium peroxide (Li2O2) and pore size distribution are investigated in lithium-O2 battery electrodes at different states of charge using transmission X-ray microscopy coupled with Zernike phase contrast to carry out nanocomputed tomog. It is reported that such a technique enables, at the nanoscale, to distinguish light elements such as carbon and Li2O2 in Li-O2 battery cathode electrodes. It is verified by wave-propagation simulation that this approach efficiently improves the contrast of images in comparison with pure absorption. The Li2O2 distribution and thickness, interphases, and pore network are visualized and quantified, giving a valuable insight into the cathode architecture. From this 3D anal., modifications are highlighted of the air-cathode morphol. and the Li2O2 spatial organization as well as their potential implication in terms of carbon surface passivation and pore-clogging. After the full recharge process, this technique can also reveal the spatial distribution of the residual Li2O2 and other byproducts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXlsFKks74%253D&md5=e4a46afa027aff80ef84aa2f705eb189
    46. 46
      Gürsoy, D.; De Carlo, F.; Xiao, X.; Jacobsen, C. TomoPy: A Framework for the Analysis of Synchrotron Tomographic Data. J. Synchrotron Radiat. 2014, 21, 1188– 1193,  DOI: 10.1107/S1600577514013939
      [Crossref], [PubMed], [CAS], Google Scholar
      46
      TomoPy: a framework for the analysis of synchrotron tomographic data
      Gursoy Doga; De Carlo Francesco; Xiao Xianghui; Jacobsen Chris
      Journal of synchrotron radiation (2014), 21 (Pt 5), 1188-93 ISSN:.
      Analysis of tomographic datasets at synchrotron light sources (including X-ray transmission tomography, X-ray fluorescence microscopy and X-ray diffraction tomography) is becoming progressively more challenging due to the increasing data acquisition rates that new technologies in X-ray sources and detectors enable. The next generation of synchrotron facilities that are currently under design or construction throughout the world will provide diffraction-limited X-ray sources and are expected to boost the current data rates by several orders of magnitude, stressing the need for the development and integration of efficient analysis tools. Here an attempt to provide a collaborative framework for the analysis of synchrotron tomographic data that has the potential to unify the effort of different facilities and beamlines performing similar tasks is described in detail. The proposed Python-based framework is open-source, platform- and data-format-independent, has multiprocessing capability and supports procedural programming that many researchers prefer. This collaborative platform could affect all major synchrotron facilities where new effort is now dedicated to developing new tools that can be deployed at the facility for real-time processing, as well as distributed to users for off-site data processing.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2M%252Fns1egsA%253D%253D&md5=ccc0e7c4b6dbc42112094f7abc0933d6
    47. 47
      Pelt, D. M.; Gürsoy, D.; Palenstijn, W. J.; Sijbers, J.; De Carlo, F.; Batenburg, K. J. Integration of TomoPy and the ASTRA Toolbox for Advanced Processing and Reconstruction of Tomographic Synchrotron Data. J. Synchrotron Radiat. 2016, 23, 842– 849,  DOI: 10.1107/S1600577516005658
      [Crossref], [PubMed], [CAS], Google Scholar
      47
      Integration of TomoPy and the ASTRA toolbox for advanced processing and reconstruction of tomographic synchrotron data
      Pelt, Daniel M.; Guersoy, Doga; Palenstijn, Willem Jan; Sijbers, Jan; De Carlo, Francesco; Batenburg, Kees Joost
      Journal of Synchrotron Radiation (2016), 23 (3), 842-849CODEN: JSYRES; ISSN:1600-5775. (International Union of Crystallography)
      The processing of tomog. synchrotron data requires advanced and efficient software to be able to produce accurate results in reasonable time. In this paper, the integration of two software toolboxes, TomoPy and the ASTRA toolbox, which, together, provide a powerful framework for processing tomog. data, is presented. The integration combines the advantages of both toolboxes, such as the user-friendliness and CPU-efficient methods of TomoPy and the flexibility and optimized GPU-based reconstruction methods of the ASTRA toolbox. It is shown that both toolboxes can be easily installed and used together, requiring only minor changes to existing TomoPy scripts. Furthermore, it is shown that the efficient GPU-based reconstruction methods of the ASTRA toolbox can significantly decrease the time needed to reconstruct large datasets, and that advanced reconstruction methods can improve reconstruction quality compared with TomoPy's std. reconstruction method.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xntlyjur0%253D&md5=baf8ee368680fc345eea8b72a46efb3c
    48. 48
      Arganda-Carreras, I.; Kaynig, V.; Rueden, C.; Eliceiri, K. W.; Schindelin, J.; Cardona, A.; Sebastian Seung, H. Trainable Weka Segmentation: A Machine Learning Tool for Microscopy Pixel Classification. Bioinformatics 2017, 33, 2424– 2426,  DOI: 10.1093/bioinformatics/btx180
      [Crossref], [PubMed], [CAS], Google Scholar
      48
      Trainable Weka Segmentation: a machine learning tool for microscopy pixel classification
      Arganda-Carreras, Ignacio; Kaynig, Verena; Rueden, Curtis; Eliceiri, Kevin W.; Schindelin, Johannes; Cardona, Albert; Seung, H. Sebastian
      Bioinformatics (2017), 33 (15), 2424-2426CODEN: BOINFP; ISSN:1460-2059. (Oxford University Press)
      State-of-the-art light and electron microscopes are capable of acquiring large image datasets, but quant. evaluating the data often involves manually annotating structures of interest. This process is time-consuming and often a major bottleneck in the evaluation pipeline. To overcome this problem, we have introduced the Trainable Weka Segmentation (TWS), a machine learning tool that leverages a limited no. of manual annotations in order to train a classifier and segment the remaining data automatically. In addn., TWS can provide unsupervised segmentation learning schemes (clustering) and can be customized to employ user-designed image features or classifiers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitFOntb%252FO&md5=1ed8765ecade6d2bab39b3f9a3d334cc
    49. 49
      Cooper, S. J.; Bertei, A.; Shearing, P. R.; Kilner, J. A.; Brandon, N. P. TauFactor: An Open-Source Application for Calculating Tortuosity Factors from Tomographic Data. SoftwareX 2016, 5, 203– 210,  DOI: 10.1016/j.softx.2016.09.002
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    50. 50
      Blanquer, G.; Yin, Y.; Quiroga, M. A.; Franco, A. A. Modeling Investigation of the Local Electrochemistry in Lithium-O2 Batteries: A Kinetic Monte Carlo Approach. J. Electrochem. Soc. 2016, 163, A329– A337,  DOI: 10.1149/2.0841602jes
      [Crossref], [CAS], Google Scholar
      50
      Modeling Investigation of the Local Electrochemistry in Lithium-O2 Batteries: A Kinetic Monte Carlo Approach
      Blanquer, Guillaume; Yin, Yinghui; Quiroga, Matias A.; Franco, Alejandro A.
      Journal of the Electrochemical Society (2016), 163 (3), A329-A337CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      In this paper we present a mesoscopic model of the transport and electrochem. processes inside a Lithium-O2 battery cathode pore. The model dynamically resolves both Oxygen Redn. Reaction (ORR) thin film and soln. phase mechanisms together with the transport of O2, Li+ and LiO2 in the electrolyte. It is supported on an extension to three dimensions of our Kinetic Monte Carlo (KMC) Electrochem. Variable Step Size Method (E-VSSM) recently published by M. A. Quiroga and A. A. Franco (2015). The model allows predicting porosity evolution as a function of multiple operational, phys. and geometrical parameters including the pore size and inlet/outlet channel size, O2 and Li+ concn., the property of the solvent as well as the applied overpotential. The investigation of the impact of these different aspects reveals that at the mesoscale level, the overall ORR kinetics and the discharge mechanism strongly depend on a balance between the geometrical features of the pore and the transport as well as the electrochem. properties of the system.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xos1Wntw%253D%253D&md5=7b937a2ae746b576001e48e3b2798e4a
    51. 51
      Reuter, K. First-Principles Kinetic Monte Carlo Simulations for Heterogeneous Catalysis: Concepts, Status, and Frontiers. Modeling and Simulation of Heterogeneous Catalytic Reactions: From the Molecular Process to the Technical System; John Wiley & Sons, Ltd: 2011; 71– 111.
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    52. 52
      Griffith, L. D.; Sleightholme, A. E. S.; Mansfield, J. F.; Siegel, D. J.; Monroe, C. W. Correlating Li/O2 Cell Capacity and Product Morphology with Discharge Current. ACS Appl. Mater. Interfaces 2015, 7, 7670– 7678,  DOI: 10.1021/acsami.5b00574
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      52
      Correlating Li/O2 Cell Capacity and Product Morphology with Discharge Current
      Griffith, Lucas D.; Sleightholme, Alice E. S.; Mansfield, John F.; Siegel, Donald J.; Monroe, Charles W.
      ACS Applied Materials & Interfaces (2015), 7 (14), 7670-7678CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The discharge rate is crit. to the performance of Li/O batteries: it impacts both cell capacity and discharge-phase morphol., and in so doing may also affect the efficiency of the O-evolution reaction during recharging. First-discharge data from tens of Li/O2 cells discharged across four rates are analyzed statistically to inform these connections. In the practically significant superficial current-d. range of 0.1 to 1 mA cm-2, capacity is found to fall as a power law, with a Peukert's-law exponent of 1.6 ± 0.1. X-ray diffractometry confirms the dominant presence of cryst. Li2O2 in the discharged electrodes. A completely air-free sample-transfer technique was developed to implement SEM of the discharge product. SEM imaging of electrodes with near-av. capacities provides statistically significant measures of the shape and size variation of electrodeposited Li2O2 particles with respect to discharge current. At lower rates, typical toroidal particles are obsd. that are well approximated as cylindrical structures, whose av. radii remain relatively const. as discharge rate increases, whereas their av. heights decrease. At the highest rate studied, air-free SEM shows that particles take needle-like shapes rather than forming the nanosheets or compact films described elsewhere. Av. particle vols. decrease with current while particle surface-to-vol. ratios increase dramatically, supporting the notion that Li2O2 grows by a locally mass-transfer-limited nucleation and growth mechanism.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXksFSrtr0%253D&md5=cd13a7bdf01cee1751be0ee315f89fa7
    53. 53
      Bruggeman, D. A. G. Berechnung Verschiedener Physikalischer Konstanten von Heterogenen Substanzen. I. Dielektrizitätskonstanten Und Leitfähigkeiten Der Mischkörper Aus Isotropen Substanzen. Ann. Phys. 1935, 416, 636– 664,  DOI: 10.1002/andp.19354160705
      [Crossref], Google Scholar
      There is no corresponding record for this reference.

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