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Energy, Environmental, and Catalysis Applications

Preinserted Ammonium in MnO2 to Enhance Charge Storage in Dimethyl Sulfoxide Based Zinc-Ion Batteries
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  • Wathanyu Kao-ian
    Wathanyu Kao-ian
    Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
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  • Jinnawat Sangsawang
    Jinnawat Sangsawang
    Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
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  • Mohan Gopalakrishnan
    Mohan Gopalakrishnan
    Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
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    Orcidhttps://orcid.org/0000-0003-4537-7170
  • Suttipong Wannapaiboon
    Suttipong Wannapaiboon
    Synchrotron Light Research Institute, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
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    Orcidhttps://orcid.org/0000-0002-6765-9809
  • Athis Watwiangkham
    Athis Watwiangkham
    Department of Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand
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  • Siriporn Jungsuttiwong
    Siriporn Jungsuttiwong
    Department of Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand
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    Orcidhttps://orcid.org/0000-0001-5943-6878
  • Jayaraman Theerthagiri
    Jayaraman Theerthagiri
    Core-Facility Center for Photochemistry & Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea
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  • Myong Yong Choi*
    Myong Yong Choi
    Core-Facility Center for Photochemistry & Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0001-5729-5418
  • Soorathep Kheawhom*
    Soorathep Kheawhom
    Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
    Center of Excellence on Advanced Materials for Energy Storage, Chulalongkorn University, Bangkok 10330, Thailand
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-3129-2750
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ACS Applied Materials & Interfaces

Cite this: ACS Appl. Mater. Interfaces 2024, 16, 42, 56926–56934
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https://doi.org/10.1021/acsami.4c07239
Published August 30, 2024

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Abstract

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Nonaqueous zinc-ion batteries (NZIBs) featuring manganese dioxide (MnO2) cathodes position themselves as viable options for large-scale energy storage systems. Herein, we demonstrate the use of ammonium cation as a preintercalant to improve the performance of the δ-MnO2 cathode in wet dimethyl sulfoxide based electrolytes. Employing in situ X-ray absorption spectroscopy, Raman spectroscopy, and synchrotron X-ray diffraction, we reveal that the integration of ammonium cations promotes the formation of NH–O–Mn networks. These networks are crucial for manipulating the distortion of the MnO6 octahedral units during discharging, thereby mitigating charge disproportionation, which is a primary limitation to MnO2’s charge-storage efficiency. The modified MnO2, through this idea, displays a notable improvement in capacity (∼247 mAh/g) and can pass charge–discharge cycles up to 500 cycles with a capacity retention of 85%. These findings underscore the potential of modified MnO2 in advancing MnO2-based hosts for Zn-MnO2 batteries, marking significant progress toward next-generation energy storage solutions.

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1. Introduction

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Due to their cost-effectiveness and environmental friendliness, the quest for sustainable energy solutions has brought zinc (Zn)-manganese dioxide (MnO2) rechargeable batteries into the spotlight. (1−3) Zn-MnO2 batteries are celebrated for their promising potential owing to their abundant availability and low cost compared to lithium-ion systems. (4,5) Despite their potential, these batteries face challenges such as hydrogen evolution and dendritic growth, limiting their practical application. (6−8) To address these issues, researchers have turned to nonaqueous electrolytes, including organic solvents, deep eutectic solvents, and ionic liquids. (9) These alternatives, notable for their nonprotonated nature, effectively prevent Zn dendrite formation by promoting the natural formation of a functional Zn–electrolyte interface, thereby enhancing the anode’s cycle life and performance. (10,11) However, utilization of these electrolytes in MnO2-based ZIBs encounters significant hurdles due to the high overpotential required for Zn-ion (Zn2+) intercalation at the MnO2 cathode. This matter leads to reduced voltage and specific capacity, limiting the batteries’ effectiveness for practical applications. (1)
Understanding of the charge-storage mechanism of MnO2 in nonaqueous media remains limited. Han et al. highlighted this by showcasing the reversible intercalation of Zn2+ into layered MnO2 (δ-MnO2) within an acetonitrile-based electrolyte, achieving a specific capacity of 123 mAh/g. However, this outcome falls short of MnO2’s theoretical capacity of 308 mAh/g, which is expected when the oxidation state of manganese is reduced by 1. (12) This discrepancy is attributed to the high charge density of the divalent Zn2+, which fosters a strong solvation effect with the solvent molecules, leading to substantial energy losses during desolvation processes. (13,14) Additionally, this high charge density intensifies the electrostatic interaction between Zn2+ ions and the oxygen atoms in MnO2, consequently impeding the solid-phase diffusion of Zn2+ and further compromising the material’s charge-storage efficiency. (15)
Innovative strategies to augment the charge-storage capacity of MnO2 have identified the addition of water as a remarkably effective method. (13,15−17) This method leverages the formation of a hydration shell around Zn2+ ions, which effectively reduces the “effective charge” of Zn2+. By diminishing the electrostatic interactions between Zn2+ ions and cathode materials, such an approach greatly facilitates the intercalation of Zn2+ ions into a variety of cathode materials, including vanadium oxides (V2O5, V6O13), vanadium phosphates (VOPO4, VPO4F), and Prussian blue analogues (KCuHCf). (13,17−20) Our research group has previously demonstrated the beneficial impact of water in a wet dimethyl sulfoxide (DMSO) electrolyte on the charge-storage capabilities of MnO2. (15) Our findings revealed a substantial increase in cathode capacity, from approximately 90 mAh/g to around 200 mAh/g at a current density of 50 mA/g, alongside improved stability with just 5 wt % water content. Despite these advancements in performance through hydration, it is suggested that optimizing the structural configuration of MnO2 could lead to further improvements in capacity.
Enhancing the performance of MnO2 as a cathode material for ZIBs can be achieved by various approaches. One method involves doping MnO2 with transition metals such as iron (Fe), cobalt (Co), and nickel (Ni). This strategy disrupts the periodic potential field inherent in MnO2, thereby improving Zn2+ ion mobility. (21) Another approach is to anchor MnO2 onto carbon supports, which not only enhances the electronic conductivity through a more robust electronic network but also helps in mitigating the dissolution of manganese. (22) When considering nonaqueous media, however, challenges extend beyond the solid-phase diffusion of Zn2+ and the poor electronic conductivity of MnO2. Such challenges encompass the desolvation process that solvated Zn2+ ions undergo prior to intercalation. Transition metal doping and the introduction of carbon supports, while beneficial, do not comprehensively address these multifaceted issues. Our investigation reveals that during the Zn2+ intercalation (discharging) process, there is a conspicuous substitution of solvated organic molecules with water molecules at the MnO2 interface. (15) This observation suggests the necessity for a functional junction capable of facilitating this exchange to enhance performance. In this context, the ammonium (NH4+) cation emerges as a promising solution. With its strong hydrogen-bonding capability and affinity for water, NH4+ can potentially alleviate the aforementioned hurdles. Despite some studies demonstrating the use of preinserted NH4+ species to enhance ZIB performance, the specific role and the effect of NH4+ in nonaqueous or wet nonaqueous ZIBs remains underexplored. (23−25)
In this study, we introduce a pioneering approach by incorporating NH4+ preintercalated manganese dioxide (NH4-MnO2) as the cathode material in wet nonaqueous ZIBs. Our goal of this work is to address the challenges of high overpotential and improve charge-storage efficiency. We utilize a DMSO-based electrolyte with an optimized concentration of Zn triflate (0.3 M) in a 5 wt % water–DMSO solution, adhering to rules established in our previous research. (15) This study aims to shed light on how NH4+ preintercalation influences the charge-storage dynamics of the MnO2 cathode. Our method is distinguished from others by employing an Mn-ion-free electrolyte, thus ensuring that the cathode’s specific capacity is unaffected by external Mn sources. To verify the successful synthesis and structural integrity of our materials, we conduct comprehensive characterizations using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and electron paramagnetic resonance (EPR). We also employ advanced X-ray techniques, including in situ X-ray absorption spectroscopy (XAS) and synchrotron XRD, to examine the valency and structural evolution of Mn and Zn within the cathode under real-cell conditions. The innovative investigation is expected to significantly contribute to the development of MnO2-based cathodes, offering valuable insights for designing practical cathode materials for ZIB applications in the future.

2. Experimental Setup and Testing

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2.1. Materials

Zn foil (99.99%, thickness: 0.05 mm) was purchased from Shandong AME Energy Co. Ltd., China. Graphite foil (grafoil, thickness: 25 μm) was purchased from Shenzhen 3KS Electronic Material Co. Ltd., China. Polyimide tape was purchased from DuPont de Nemours, Inc. Ketjenblack EC-600JD electroconductive carbon black was purchased from Ketjen International. Solef 5130 (PVDF for Li-ion batteries) was purchased from Solvay. Ammonium persulfate ((NH4)2S2O8, 98%), anhydrous DMSO (99.9%), sodium carboxymethylcellulose (NaCMC, medium viscosity), and Zn triflate (Zn(CF3SO3)2, 98%) were procured from Sigma-Aldrich. Ammonia solution (NH3, 28%) was acquired from QReC. Potassium permanganate (KMnO4, 99.0%) was obtained from Ajax Finechem. Glass microfiber (WHA1820125, GF/A, pore size: 1.6 μm) was purchased from Whatman Plc.

2.2. K-MnO2 and NH4-MnO2 Syntheses

Potassium-MnO2 (K-MnO2, δ-phase) was synthesized via a hydrothermal method. (15,26,27) First, 70 mL of deionized (DI) water was used to dissolve 1.896 g of KMnO4; the mixture was agitated at a medium rotating speed. After 30 min, 0.338 g of MnSO4·H2O was gradually added to the solution. Subsequently, the mixture was placed in an autoclave lined with PTFE and heated to 160 °C for 24 h. The autoclave was then allowed to cool naturally in the open air. Finally, the mixture was filtered, repeatedly cleaned with ethanol and DI water, and then vacuum-dried overnight at 60 °C.
For the NH4-MnO2 preparation, K-MnO2 was used as a precursor. Wang et al. used the method adapted from the TMA-MnO2 preparation. (28) First, 0.4 g of K-MnO2 was mixed with 100 mL of 0.5 M (NH4)2S2O8 under vigorous stirring at 60 °C for 12 h. Then, the filtered solid was dried at 60 °C in an oven. Subsequently, 0.4 g of the obtained powder (proton-intercalated MnO2) was neutralized using 100 mL of 10 wt % NH3 solution (NH4OH). The mixture was stirred at a medium rotating speed for 3 days. The product, NH4-MnO2, was obtained after being filtrated and dried at 60 °C overnight.

2.3. Cathode and Electrolyte Preparation

Both MnO2 (70 wt %), Ketjenblack (20 wt %), and NaCMC (10 wt %) were slurry mixed with deionized (DI) water to form an ink for the cathode coating. To ensure homogeneity, the mixture was shaken and agitated several times using an ultrasonic cleaner and magnetic stirrer. Subsequently, the ink was applied on the graphite foil using a doctor blade (AOT-FCM-250, AOT Electronic Technology) and left until dry for 2 h. Then, the coated cathode was rolled using a laboratory roller press machine (TOB-DG-100L). Finally, the cathode was vacuum-dried at 60 °C overnight. The average δ-MnO2 loading on the electrode was ∼2 mg/cm2. The electrolyte was prepared by simply mixing 5 wt % water in DMSO. Finally, Zn triflate was mixed with 5 wt % water in DMSO in a volumetric flask to form a 0.3 M Zn triflate solution.

2.4. Electrochemical Measurements and Material Characterizations

A button cell (CR2025) was used as the main configuration for the electrochemical measurement. Using a punching machine (TOB-CP60), the Zn foil (anode) and MnO2 (cathode) were cut into 15 mm diameter disks. A glass microfiber (19 mm in diameter) was used as a separator. The cell was assembled, and 250 μL of electrolyte was added to the cell. Finally, a coin cell crimping machine (TOB-MR120) was used to seal the cell. To determine the rate capability, cyclability, and discharging overpotential of the battery, both galvanostatic charge–discharge (GCD) and galvanostatic intermittent titration technique (GITT) were carried out using a battery analyzer (NEWARE, BTS4000-5 V10 mA). To investigate the redox behavior of the battery, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed using a potentiostat (Squidstat, Admiral Instruments LLC). All of the electrochemical measurements were performed in a cell isolating the thermal safety chamber (Arbin instruments) at a regulated temperature of 30 °C.
Further, to speciate and analyze their properties, synthesized powders, namely, K-MnO2 and NH4-MnO2, were analyzed using TEM-EDS (JEOL Model JEM-2100), XPS (PHI VersaProbe 4), ex situ XRD (Cu Kα radiation, 40 kV, 15 mA, and λ = 1.5418 Å, Aeris Benchtop, Malvern Panalytical, U.K.), FT-IR (Thermo Fisher Nicolet iS5 FT-IR spectrometer), Raman (Thermo Scientific DXR Raman Microscopy), and EPR (BRUKER EMXmicro). To capture the morphology and the composition of the δ-cathode, FE-SEM (QuantaTM 250 FEG (FEI)) with EDX (PentaFET, Oxford Instruments) was employed. To determine the charge-storage mechanism and discern the difference between K-MnO2 and NH4-MnO2 cathodes, synchrotron XRD and in situ XAS results were collected at beamline 1.1, Synchrotron Light Research Institute (SLRI), Thailand. Synchrotron XRD was performed at 12 keV and calibrated λ of 1.033198 Å using the grazing incidence mode, which is well-suited for analyzing a thin film. In situ XAS was measured using a homemade cell (Figure S1), which was designed for the transmission XAS mode. To obtain high-quality XAS data, the amount of cathode material loading was carefully determined (2.0 mg/cm2). XAS results, namely, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), were interpreted using Demeter: XAS data processing and analysis version 0.9.26. (29)

3. Results and Discussion

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In Figure 1, the characterization results of the synthesized K-MnO2 and NH4-MnO2 powders are shown. As observed via TEM, both K-MnO2 (Figure 1A) and NH4-MnO2 (Figure 1D) reveal a flower-like nanostructure, similar to other forms of δ-MnO2 as seen in the literature. (30,31) EDS mapping of K-MnO2, in accordance with the TEM image, indicates an even distribution of Mn (Figure 1B) and K (Figure 1C) along the MnO2 grain; the latter refers to the intercalated K in the interlayer of MnO2. In Figure 1E, the distribution of Mn in NH4-MnO2 is displayed. It is noted that EDS of the NH4-MnO2 sample displays a weaker signal of K (Figure 1F) than that of N (Figure 1G), indicating the substitution of N-containing species at the K site. In addition, N species were also detected via the XPS technique (Figure S2). The deconvoluted peaks of the narrow scan during N 1s energy indicate the existence of N–H (399.85 eV) and N–H+ (401.63 eV). (32,33) In Figure 1H,I, the zoom-in TEM images display a clear interplanar spacing of MnO2, which is attributed to the 001 plane. Both the K-MnO2 and NH4-MnO2 samples show a similar interspacing distance of ∼0.69 nm. In Figure 1J, the XRD spectrum of K-MnO2 is well-matched with birnessite (ref code 96-901-0157, H4K0.23MnO2.776), signifying main characteristic peaks at 2θ of 12.35° (001), 24.9° (002), and 36.5° (11–1). The NH4-MnO2 sample exhibits peaks of 001 and 002 planes at a slightly lower angle compared to that of K-MnO2, indicating that after modification, the interspacing length between the MnO2 layers increased. According to the refined XRD spectra using the Rietveld refinement technique (Figure S3 and Table S1), the d-spacings of the 001 plane of K-MnO2 and NH4-MnO2 are 7.17 and 7.24 Å, respectively. An increase in interspacing is attributed to the presence of the interlayered NH4+ (ion radii: 1.40–1.67 Å), which is larger than the potassium (K) ion (ion radii: 1.38 Å). (34,35) In addition, the 11–1 peak (inset in Figure 1J, right) slightly shifted from its own position. Such a shift indicates that the geometrical distortion of MnO6 occurred when NH4+ was present.

Figure 1

Figure 1. Powder characterization results: (A) TEM image of K-MnO2, (B) Mn EDS mapping of K-MnO2, (C) K EDS mapping of K-MnO2, (D) TEM image of NH4-MnO2, (E) Mn EDS mapping of NH4-MnO2, (F) K EDS mapping of NH4-MnO2, (G) N EDS mapping of NH4-MnO2, (H) zoom-in TEM image of K-MnO2, (I) zoom-in TEM image of NH4-MnO2, (J) XRD results of K-MnO2 and NH4-MnO2, (K) FT-IR results, (L) structure of the synthesized NH4-MnO2, (M) deconvoluted Raman spectra of K-MnO2, and (N) deconvoluted Raman spectra of NH4-MnO2.

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In Figure 1K, FT-IR results are shown. Thus, it is seen that there are about three regions of FT-IR spectra, i.e., wavenumber >700, 1350–1670, and 2950–3550 cm–1, which are ascribed to the stretching vibration of Mn–O, the stretching vibration of O–H, and the stretching vibration of N–H/O–H, respectively. (36) During 2950–3550 cm–1, additional peaks appeared in NH4-MnO2. In contrast, the K-MnO2 sample did not show such characteristics. These peaks are attributed to the presence of the N–H stretching vibration of NH4+ cations and their interaction with oxygen atoms from MnO2 or water molecules. At 1410 cm–1, the peak intensified, indicating the presence of the bending vibration of N–H along with the stretching vibrational mode of the water molecule in the MnO2 interlayer. (37) At this point, the existence of the NH4+ cation in the MnO2 interlayer is confirmed. In Figure 1L, the structure of the synthesized NH4-MnO2 is illustrated.
In Figure 1M,N, the deconvolution of the Raman results of K-MnO2 and NH4-MnO2 is illustrated. Herein, ν1, ν2, and ν3 are attributed to the Mn–O lattice vibration of the basal plane of the MnO2 sheets and the Mn–O lattice vibration and the symmetric stretching vibration of the Mn–O band in the MnO6 octahedra, respectively. (37−39) It is seen that after transforming K-MnO2 into NH4-MnO2, the contribution of ν1 to the Raman curve reduced, indicating that the binding force between the upper and lower layer of the MnO2 increased. This increase is due to the strong hydrogen bond formed between the oxygen atoms of MnO2 and the hydrogen atoms of the NH4+ cations in the interlayer of MnO2. Moreover, peak ν3 shifted to a higher wavenumber, denoting that the stability of Mn–O bonds within the MnO6 octahedra increased. It is noted that NH4+ cations act like a pillar and form NH–O–Mn, exhibiting a strong binding force between layers of MnO2 and slight distortion of MnO6 from its own shape having Mn(IV). In Figure S4, the EPR signal of NH4-MnO2 is seen to be weaker than that of K-MnO2. Thus, the modification did not increase the number of unpaired electrons or oxygen vacancies. (40,41)
In Figure 2, the electrochemical performance of wet nonaqueous ZIBs having K-MnO2 and NH4-MnO2 cathodes is shown. In Figure 2A, after potassium atoms were substituted with NH4+ cations, the initial discharge capacity of the MnO2 cathode and the cell voltage significantly increased (specific capacity from 195 to 247 mAh/g and cell voltage from 0.95 to 1.04 V at a current density of 50 mA/g). As for the rate capability test (Figure 2B), NH4-MnO2 displayed an average specific capacity of 207, 176, 164, 155, 141, and 111 mAh/g at current densities of 50, 100, 150, 200, 300, and 500 mA/g, respectively. These findings are superior to those of K-MnO2 (177, 150, 139, 129, 103, and 72 mAh/g at 50, 100, 150, 200, 300, and 500 mA/g, respectively). In Figure 2C,D, both the K-MnO2 and NH4-MnO2 samples exhibited higher average discharge voltages compared with that in the first cycle and were not much different from each other. However, at high current densities (300 and 500 mA/g), the NH4-MnO2 sample tends to have a higher rate capability. Due to the high overpotential of the Zn anode, a low voltage during the first cycle occurred, as observed in Figure S5. The first charging may be attributed to the formation of the SEI at the Zn anode, which mobilized the plating/stripping of Zn. Nevertheless, this issue is beyond the scope of this study. Thus, it will be discussed in future publications.

Figure 2

Figure 2. Results of electrochemical performance: (A) GCD results at the first cycle, (B) rate capability, voltage profile vs specific capacity using GCD of (C) K-MnO2 and (D) NH4-MnO2, (E) CV results, (F) GITT results, and (G) cyclability results.

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In Figure 2E, CV results at a scan rate of 0.2 mV/s are shown. It is seen that both the K-MnO2 and NH4-MnO2 samples display at least two reduction peaks and two oxidation peaks. This outcome indicates that there are at least two redox reactions involved in the charge-storage mechanism of MnO2 in this electrolyte. When compared with K-MnO2, the NH4-MnO2 sample exhibited better redox kinetics, as can be seen via the higher current density trend along the IV-axis. In addition, the intensity of both oxidation and reduction peaks increased, thus indicating the improved diffusion limit of ions involved in the charge-storage reaction when NH4+ was introduced.
In Figure S6, peaks 1, 2, 3, and 4, which appeared in the CV results, were analyzed using Dunn’s methodology. (42) Thus, all peaks of the K-MnO2 samples revealed b-values of 0.673, 0.607, 0.688, and 0.723, respectively. In contrast, the b-values of the NH4-MnO2 sample were 0.690, 0.661, 0.691, and 0.750, respectively. It is seen that all b-values <0.75 signify that the charge-storage mechanism of both the K-MnO2 and NH4-MnO2 samples was a mixture of capacitive-controlled and diffusion-controlled behavior. The NH4-MnO2 sample exhibited slightly higher b-values in every peak compared to that of the K-MnO2 sample, indicating faster charge-storage kinetics upon charging and discharging.
Further, GITT was conducted using a rest period of 2 h and a discharging current density of 100 mA/g for 5 min. In Figure 2F, the results are given. During 0–20 h of GITT, the voltage profiles of K-MnO2 and NH4-MnO2 were almost similar to each other, indicating the similar diffusivity of guest ions in these samples upon the start of discharging. After 20 h of GITT, the size of the discharging overpotential of K-MnO2 started to overcome that of the NH4-MnO2 sample. In Figure S7, the plot of calculated diffusivity versus state of charge (SOC) signifies a significant improvement in the diffusivity of guest ions in the MnO2 structure when NH4+ was presented. In addition, EIS results (Figure S8 and Table S2) demonstrate the minimized charge-transfer resistance of the cathode. When NH4+ is introduced onto MnO2, the diffusion of guest ions can be mobilized, thus improving the kinetics of these ions upon the intercalation reaction. Such an outcome results in higher specific capacity and superior rate performance of the cathode having preintercalated NH4+ and agrees well with the GCD and CV results.
In Figure 2G, both the cycling stabilities of the K-MnO2 and NH4-MnO2 samples are measured and illustrated. Initially, the K-MnO2 and NH4-MnO2 samples displayed specific capacities of 118 and 169 mAh/g, respectively (current density 200 mA/g). After 500 cycles, the specific capacity of the K-MnO2 and NH4-MnO2 samples decreased to 96 and 143 mAh/g, yielding capacity retention of 81 and 85%, respectively. The results show that in terms of stability, both the K-MnO2 and NH4-MnO2 samples are found to be about the same. Nevertheless, in terms of specific capacity, the NH4-MnO2 sample clearly outnumbered K-MnO2.
In Figure 3A, the synchrotron XRD (λ = 1.033 Å) results of K-MnO2 and NH4-MnO2 after the fifth cycle are shown. Hence, XRD spectra reveal both birnessite characteristics and chalcophanite (ZnMn3O7·3H2O) characteristics at the charged state of the K-MnO2 and NH4-MnO2 samples. (43,44) XPS results of the charged K-MnO2 cathode display a trace of Zn2+ remaining in the cathode (Figure S9). In addition, EXAFS results (Figure S10 and Table S3) of both K-MnO2 and NH4-MnO2 are well-matched with the ZnMn3O7·3H2O structure, as in the literature. (43,45) Thus, the formation of chalcophanite after the first charge/discharge was confirmed. After discharging, the intensity of the chalcophanite characteristic peaks decreased. Further, characteristics of Zn oxide (ZnO; 2θ of 21.1, 22.9, 24.1, 31.5, 37.1, 40.9, and 44.0°) were observed in the XRD spectra of both the K-MnO2 and NH4-MnO2 samples at the discharged state, indicating the formation of ZnO upon discharging at the cathode. (46) In Figure S11, small white pellets were detected via FE-SEM in the discharged cathode. However, these ZnO precipitates were found to be highly reversible (Figure S12). Such a by-product reflects that the dissociation of water, i.e., proton (H+), could be involved in the charge storage of these cathodes. The remaining hydroxide anions could result in the formation of hydroxozincate; accordingly, an oversaturated content of hydroxozincate at the cathode–electrolyte interface led to the formation of ZnO. (47) Although the XRD results cannot provide clear information regarding the phase transformation of K-MnO2 and NH4-MnO2 after discharging, it can be inferred that their “birnessite-like” characteristics still existed. In Figure S13, the Raman spectra of the discharged cathodes indicate the existence of ν1, ν2, and ν3, which are characteristic of the layers of the MnO6 octahedra. (48)

Figure 3

Figure 3. Charge-storage mechanism determination results: (A) synchrotron XRD results of K-MnO2 and NH4-MnO2 at charge/discharge state (after fifth cycle), (B, C) XANES spectra measured via in situ XAS technique, (D, E) density functional theory (DFT)-optimized models and plots of the partial density of states (PDOS), (F) zoom-in image of the XANES results, (G) in-situ EXAFS of K-MnO2 upon discharging, (H) in-situ EXAFS of NH4-MnO2 upon discharging, (I) schema of the stabilization of MnO2 using NH4+ cations, and (J) EXAFS of K-MnO2 and NH4-MnO2 at a discharged state.

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In situ XAS technique was carried out in order to probe the structural evolution of Mn in the K-MnO2 and NH4-MnO2 samples in a real-cell environment. Mn K-edge XANES spectra (Figure 3B,C) highlight the decrease in the absorption edge energy of Mn, which corresponds to the decrease in their oxidation number upon discharging. In comparison with MnO2 and Mn2O3 references, Mn(IV) and Mn(III), the absorption edge energy of both K-MnO2 and NH4-MnO2 changed within the gap of the absorption edge energy of MnO2 and Mn2O3: Mn within these cathodes tended to change from an oxidation number of almost +4 to about +3. Such an evolution indicates that the charge-storage redox reaction of these cathodes mainly relied on the valency evolution of Mn in the solid phase. (49) Both K-MnO2 and NH4-MnO2 display an evolution in the white-line area and a local vibration dynamic during the postedge region during discharging. Although the white-line part in K-edge results of Mn cannot directly exhibit the information on Mn 3d orbitals, the intensity of such a part can be used for indicating the situation in 3d orbital in case the neighboring atoms of Mn are O. (50,51) The decrease in the white-line intensity upon discharging signifies the decrease of unoccupied 3d orbitals of Mn, which corresponds to the progressive formation of the intercalated state of the guest ions from the electrolyte onto the MnO2 layers. (52)
In accordance with crystal field theory, the electronic configuration of Mn was investigated using density functional theory (DFT). Details of the simulation and the DFT-optimized models (Figure S14) are given in the Supporting Information (SI). In Figure 3D,E, the plot of the partial density of states (PDOS) is shown. After the intercalation of Zn2+, the energy of the d orbital (εd-Mn) of the K-MnO2 shifts −0.28 eV. In contrast, the NH4-MnO2 displays the εd-Mn shift of −0.19 eV, implying that the d orbitals of Mn in the NH4-MnO2 possess higher stability. Such a result was also confirmed by analyzing the pre-edge part of the XANES spectra (Figure 3F). As such, this pre-edge part is ascribed to the excitation of 1s–3d orbitals. The curves, marked at two points, correspond to the orbitals of Mn 3d, which bonded with 2p orbitals of the neighboring O, viz., t2g and eg. The height of these peaks corresponds to the unoccupied degree of such orbitals. (53) Upon discharge, it is seen that the intensity of the eg peak of K-MnO2 decreased dramatically. Evolution of the K-MnO2 sample indicates that Mn(III) having t2g3eg1 was formed upon discharging, thus resulting in the splitting of eg into different energy levels. Hence, the Jahn–Teller (JT) distortion of MnO6 units occurred. (54) It is noted that the NH4-MnO2 sample did not show a severe drop in the size of the eg peak. This outcome denotes that the splitting in the energy of the eg orbital of Mn in the NH4-MnO2 sample was minimal compared to that of the K-MnO2 sample, demonstrating that MnO6 in the presence of the NH4+ cation can retain its own shape upon reduction in the oxidation number of Mn.
In Figure 3G,H, in situ EXAFS results of the K-MnO2 and NH4-MnO2 samples are shown. The spectra display two shells (Mn–O and Mn–Mn). The Mn–O shell corresponds to the bonding between the center atom (Mn) and neighboring O atoms that bonded with Mn. The Mn–Mn shell represents other Mn atoms nearby. As the discharging of the battery progressed, the intensity of Mn–O and Mn–Mn shells of both the K-MnO2 and NH4-MnO2 samples decreased. Such behavior corresponds to the degree of decentralization in the distribution of Mn–O bonding distance and Mn–Mn distance in the cathode. (55) In comparison with the NH4-MnO2 sample, the K-MnO2 sample displayed a more drastic reduction in its intensity. In addition, upon discharging, it is clearly seen that the peak position of the Mn–O shell and Mn–Mn shell of the K-MnO2 sample shifted to the left and right, respectively: this shift indicates that the MnO6 unit in the MnO2 layers started to elongate, which is the nature of MnO6 units when the oxidation number of Mn reduces from +4 to +3. In contrast, the peak position of Mn–O and Mn–Mn shells of the NH4-MnO2 sample was almost unchanged. (55) Such behavior occurs due to the formation of hydrogen bonds: NH–O–Mn interaction, which results in a “preinserted stress” toward O of MnO6 (Figure 3I). Upon discharging, the hydrogen-bonding network created by NH4+ had a role in manipulating the distortion of the remaining MnO6(IV) and MnO6(III) in the cathode. As a result, the geometrical differences between MnO6(III) and MnO6(IV) are minimized. The disproportionation issue that occurred in the K-MnO2 sample hindered the transport of guest ions during the intercalation reaction, resulting in poor kinetic of the cathode. (53,55) Hence, the introduction of the NH4+ cation can mobilize the ion migration and accelerate surface kinetic via the improved surface of MnO2 caused by hydrogen-bond networking, which promotes reduced charge disproportionation.
To clarify the speciation of the inserted species in the cathode during discharging of the battery, in situ XAS at the Zn K-edge energy was employed. In Figure 3J, the Zn K-edge EXAFS results of the discharged K-MnO2 and NH4-MnO2 are shown. The spectrum of the K-MnO2 sample displayed two shells at 1.53 and 2.91 Å, which correspond to the Zn–O bonding distancing and Zn with other metal atoms. NH4-MnO2 exhibits shells at 1.56 and 2.94 Å. The EXAFS fitting was used in order to specify the species of such a structure (Figure S15 and Table S4). K-MnO2 spectrum fitted in well with ZnO, which indicates that proton insertion highly contributed to the charge storage of the K-MnO2 sample. (46) In the NH4-MnO2 sample, its spectrum is well-matched with Zn in the chalcophanite structure; Zn insertion is more likely to contribute to charge-storage reaction rather than proton insertion. (43) Typically, migration of Zn2+ having a +2 oxidation number is hindered by a strong electrostatic impulsion between guest Zn2+ and the host structure. Consequently, a proton possesses a +1 charge and, being much smaller in size, can take the place of Zn2+ in the situation, whereby Zn2+ are not free to move, as in nonaqueous media. (56) Improvement in the mobility and surface kinetics of the cathode, influenced by the NH4+ cation, has a crucial role to play in determining charge-storage pathways and results in superior specific capacity.

4. Conclusions

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In this paper, the results demonstrate that the addition of preintercalated ammonium ions could successfully enhance the performance of wet nonaqueous ZIBs, utilizing MnO2 as a cathode material. The simultaneous presence of both distorted Mn(III) and undistorted Mn(IV) in the cathode structure is identified as a major impediment to ion migration, adversely affecting the surface kinetics of the MnO2 cathode. The introduction of ammonium, however, characterized by its robust hydrogen-bonding capability, effectively addresses the charge disproportionation challenge by forming NH–O–Mn networks. This structural innovation facilitates a more uniform geometric distortion between MnO6(IV) and MnO6(III), thereby optimizing both surface kinetics and ion transport. Such enhancements greatly elevate the role of Zn2+ insertion over proton reactions, contributing to the remarkable increase in the specific capacity. The MnO2 cathode, modified with ammonium ions, achieved an unprecedented capacity of 247 mAh/g, confirming its durability over 500 cycles with a capacity retention of 85%. These findings offer valuable insights for future MnO2 cathode development, promoting the design and application of high-performance ZIBs.

Data Availability

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The authors declare that all data supporting the findings of this study are available within the paper and its Supporting Information file.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.4c07239.

  • The electrochemical cell for the in situ XAS measurement, XPS of the NH4-MnO2 powder, Rietveld refinement results of the XRD spectra, EPR, GCD, CV, and Dunn’s analysis, diffusivity, EIS, XPS of the K-MnO2 cathode, Mn K-edge EXAFS, FE-SEM of the discharged cathodes, operando XRD of K-MnO2, Raman spectra, DFT-optimized models and description of DFT calculations, and Zn K-edge EXAFS (PDF)

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Author Information

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  • Corresponding Authors
    • Myong Yong Choi - Core-Facility Center for Photochemistry & Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea;  Orcidhttps://orcid.org/0000-0001-5729-5418;  Email: [email protected]
    • Soorathep Kheawhom - Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand;  Center of Excellence on Advanced Materials for Energy Storage, Chulalongkorn University, Bangkok 10330, Thailand;  Orcidhttps://orcid.org/0000-0002-3129-2750;  Email: [email protected]
  • Authors
    • Wathanyu Kao-ian - Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
    • Jinnawat Sangsawang - Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
    • Mohan Gopalakrishnan - Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand;  Orcidhttps://orcid.org/0000-0003-4537-7170
    • Suttipong Wannapaiboon - Synchrotron Light Research Institute, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand;  Orcidhttps://orcid.org/0000-0002-6765-9809
    • Athis Watwiangkham - Department of Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand
    • Siriporn Jungsuttiwong - Department of Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand;  Orcidhttps://orcid.org/0000-0001-5943-6878
    • Jayaraman Theerthagiri - Core-Facility Center for Photochemistry & Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea
  • Author Contributions

    W.K.-i. and S.K. were responsible for conceptualization. W.K.-i., S.W., and S.K. were responsible for methodology. W.K.-i., J.S., and S.W. performed the experiments. W.K.-i., M.G., S.W., S.J., J.T., M.Y.C., and S.K. performed the formal analysis. W.K.-i. performed visualization. S.K. was responsible for funding acquisition. S.K. supervised the study. W.K.-i. and S.K. wrote the original draft. All authors wrote, reviewed, and edited the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The Program Management Unit for Human Resources & Institutional Development, Research, and Innovation (B16F640166) is acknowledged. W.K.-i. thanks Chulalongkorn Academic Advancement into its second Century Project for Postdoctoral Fellowship. M.Y.C. acknowledges the support of the Korea Basic Science Institute (National Research Facilities and Equipment Center) grant funded by the Ministry of Education (Nos. 2019R1A6C1010042 and 2021R1A6C103A427).

References

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    Li, H. A high-performance MnO2 cathode doped with group VIII metal for aqueous Zn-ion batteries: In-situ X-Ray diffraction study on Zn2+ storage mechanism. J. Power Sources 2022, 527, 231198  DOI: 10.1016/j.jpowsour.2022.231198
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    Zhang, Y.; Deng, S.; Li, Y. Anchoring MnO2 on nitrogen-doped porous carbon nanosheets as flexible arrays cathodes for advanced rechargeable Zn–MnO2 batteries. Energy Storage Mater. 2020, 29, 52– 59,  DOI: 10.1016/j.ensm.2020.04.003
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    Yao, H.; Yu, H.; Zheng, Y. Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries. Angew. Chem., Int. Ed. 2023, 62 (51), e202315257  DOI: 10.1002/anie.202315257
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    Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries
    Yao, Haixin; Yu, Huan; Zheng, Yaqi; Li, Nian Wu; Li, Sheng; Luan, Deyan; Lou, Xiong Wen; Yu, Le
    Angewandte Chemie, International Edition (2023), 62 (51), e202315257CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Layered manganese dioxide is a promising cathode candidate for aq. Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic cond. and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K+-intercalated δ-MnO2 nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K+ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochem. properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.
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    Sun, T.; Zheng, S.; Nian, Q. Hydrogen Bond Shielding Effect for High-Performance Aqueous Zinc Ion Batteries. Small 2022, 18 (12), 2107115  DOI: 10.1002/smll.202107115
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    Fu, Y.; Jia, C.; Chen, Z. Modulating residual ammonium in MnO2 for high-rate aqueous zinc-ion batteries. Nanoscale 2022, 14 (8), 3242– 3249,  DOI: 10.1039/D1NR07406G
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    Liu, Y.; Wei, J.; Tian, Y. The structure–property relationship of manganese oxides: highly efficient removal of methyl orange from aqueous solution. J. Mater. Chem. A 2015, 3 (37), 19000– 19010,  DOI: 10.1039/C5TA05507E
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    The structure-property relationship of manganese oxides: highly efficient removal of methyl orange from aqueous solution
    Liu, Yan; Wei, Jie; Tian, Yaxi; Yan, Shiqiang
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (37), 19000-19010CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Mn oxides of various crystal structures (α-, β-, γ- and δ-MnO2, Mn2O3, Mn3O4 and amorphous) were synthesized by facile methods. The adsorption capacities for Methyl orange of these materials were studied and the resulting materials were characterized by different techniques, such as SEM, XRD and BET surface area measurements. The adsorption capacities were strongly dependent on the crystallog. structures and morphologies, and followed the order of A-MnO2 > Mn2O3 > Mn3O4 > α-MnO2 nanowires > β-MnO2 > γ-MnO2 > α-MnO2 nanotubes >δ-MnO2, while the adsorption properties could be greatly improved by increasing the surface area and pore properties of the adsorbents. A-MnO2 was the most effective adsorbent among the other materials and the adsorption process was systematically studied. The adsorption kinetics data closely followed the pseudo-2nd-order kinetic model and the results obtained from the intraparticle diffusion model indicated that the overall process was jointly influenced by external mass transfer and intra-particle diffusion. The max. adsorption capacity detd. from the Langmuir isotherm model was 1488.7 mg/g. Thermodn. analyses revealed that the adsorption of MO onto A-MnO2 was spontaneous and exothermic, and the phys. adsorption mechanisms including electrostatic interactions played a dominant role in the adsorption process between MO and A-MnO2. These combined results indicated that A-MnO2 is an efficient adsorbent for the removal of MO from wastewater.
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    Kao-ian, W.; Nguyen, M.; Yonezawa, T. Highly stable rechargeable zinc-ion battery using dimethyl sulfoxide electrolyte. Mater. Today Energy 2021, 21, 100738  DOI: 10.1016/j.mtener.2021.100738
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    Highly stable rechargeable zinc-ion battery using dimethyl sulfoxide electrolyte
    Kao-ian, W.; Nguyen, M. T.; Yonezawa, T.; Pornprasertsuk, R.; Qin, J.; Siwamogsatham, S.; Kheawhom, S.
    Materials Today Energy (2021), 21 (), 100738CODEN: MTEACH; ISSN:2468-6069. (Elsevier Ltd.)
    Due to their high safety, low cost, eco-friendliness, and impressive electrochem. performance, rechargeable zinc-ion batteries (ZIBs) show great potential as elec. energy storage devices for large-scale applications. Nonetheless, recently developed ZIBs still suffer from low cycling stability and high capacity fading. Such shortcomings are caused by the reversibility of both zinc (Zn) and the cathode host material, as well as hydrogen evolution in aq. electrolytes, which are naturally protic solvents. Herein, DMSO (DMSO), a polar aprotic solvent, is examd. as an electrolyte for a ZIB. Zn stripping/plating in DMSO-based electrolytes shows excellent reversibility and dendrite-free morphol. During charging and resting modes, hydrogen evolution is effectively inhibited. Insertion/extn. of Zn ions in DMSO-based electrolytes into delta-type manganese dioxide (δ-MnO2) demonstrates high stability, achieving a decent initial capacity of 159 mAh/g at 50 mA/g and a nominal discharge voltage of 1.15 V. At 100 mA/g charge/discharge cycling, the ZIB, having the DMSO-based electrolyte, can pass 1000 cycles, displaying a capacity retention of 60%. Overall, the improved performance of ZIBs can be attained using DMSO-based electrolytes. Results pave the way towards the practical application of ZIBs.
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    Wang, M.; Yagi, S. Layered birnessite MnO2 with enlarged interlayer spacing for fast Mg-ion storage. J. Alloys Compd. 2020, 820, 153135  DOI: 10.1016/j.jallcom.2019.153135
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    Layered birnessite MnO2 with enlarged interlayer spacing for fast Mg-ion storage
    Wang, Mengqiao; Yagi, Shunsuke
    Journal of Alloys and Compounds (2020), 820 (), 153135CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    To identify appropriate electrode active materials for application in Mg batteries, the Mg2+ storage ability of birnessite MnO2 with different interlayer spacings was investigated. The changes in the redox peak position in the cyclic voltammograms of birnessite MnO2 with different interlayer spacings confirmed the intercalation/deintercalation reactions of Mg2+ ions to/from the interlayers of layered birnessite MnO2 and their surface adsorption. The role of water mols. in the charge/discharge processes was also investigated using an electrochem. quartz crystal microbalance, and a plausible reaction mechanism was proposed. It was found that the specific capacity nearly doubled, from 58.6 to 110.8 mAh g-1, at 1 C when the interlayer spacing of birnessite MnO2 was expanded, from 0.70 to 0.97 nm, by altering the original intercalated ions. The rate capability was also significantly improved by expanding the interlayer spacing. Such excellent discharge-charge properties were ascribed to the broader diffusion channel, which enabled easier Mg2+ diffusion. The strategy reported herein provides an efficient method to fabricate outstanding active materials for application in Mg batteries and a new strategy to develop active materials for other energy storage devices.
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    Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 2005, 12 (4), 537– 541,  DOI: 10.1107/S0909049505012719
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    ATHENA, ARTEMIS, HEPHAESTUS: data analysis for x-ray absorption spectroscopy using IFEFFIT
    Ravel, B.; Newville, M.
    Journal of Synchrotron Radiation (2005), 12 (4), 537-541CODEN: JSYRES; ISSN:0909-0495. (Blackwell Publishing Ltd.)
    A software package for the anal. of x-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data anal. using theor. stds. from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of at. absorption data. These programs enable high-quality data anal. that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
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  30. 30
    Misnon, I. I.; Aziz, R. A.; Zain, N. K. M. High performance MnO2 nanoflower electrode and the relationship between solvated ion size and specific capacitance in highly conductive electrolytes. Mater. Res. Bull. 2014, 57, 221– 230,  DOI: 10.1016/j.materresbull.2014.05.044
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    30
    High performance MnO2 nanoflower electrode and the relationship between solvated ion size and specific capacitance in highly conductive electrolytes
    Misnon, Izan Izwan; Aziz, Radhiyah Abd; Zain, Nurul Khairiyyah Mohd; Vidhyadharan, Baiju; Krishnan, Syam G.; Jose, Rajan
    Materials Research Bulletin (2014), 57 (), 221-230CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
    Flower shaped birnessite type manganese oxide (δ-MnO2) nanostructures are synthesized using a simple hydrothermal process with an aim to fabricate high performance supercapacitors for energy storage electrode. The studies reveal that layered δ-MnO2 had a basal plane spacing of ∼0.73 nm and are composed of thin nanosheets of thickness ∼23 nm. A detailed investigation is undertaken to draw a relationship between the solvated ion size of alk. electrolytes (LiOH, NaOH and KOH) and pore size in the electrode material favoring high specific capacitance and faster electrode kinetics. The present work not only develops a high performance supercapacitive material but also identifies that by suitably tuning the sizes of solvated ion and the pores, supercapacitive behavior of a single material system can be tailored.
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  31. 31
    Wang, Y.; Zhang, Y.; Gao, G. Effectively Modulating Oxygen Vacancies in Flower-Like δ-MnO2 Nanostructures for Large Capacity and High-Rate Zinc-Ion Storage. Nano-Micro Lett. 2023, 15 (1), 219,  DOI: 10.1007/s40820-023-01194-3
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    31
    Effectively Modulating Oxygen Vacancies in Flower-Like δ-MnO2 Nanostructures for Large Capacity and High-Rate Zinc-Ion Storage
    Wang, Yiwei; Zhang, Yuxiao; Gao, Ge; Fan, Yawen; Wang, Ruoxin; Feng, Jie; Yang, Lina; Meng, Alan; Zhao, Jian; Li, Zhenjiang
    Nano-Micro Letters (2023), 15 (1), 219CODEN: NLAEBV; ISSN:2150-5551. (Springer International Publishing AG)
    In recent years, manganese-based oxides as an advanced class of cathode materials for zinc-ion batteries (ZIBs) have attracted a great deal of attentions from numerous researchers. However, their slow reaction kinetics, limited active sites and poor elec. cond. inevitably give rise to the severe performance degrdn. To solve these problems, herein, we introduce abundant oxygen vacancies into the flower-like δ-MnO2 nanostructure and effectively modulate the vacancy defects to reach the optimal level (δ-MnO2-x-2.0). The smart design intrinsically tunes the electronic structure, guarantees ion chemisorption-desorption equil. and increases the electroactive sites, which not only effectively accelerates charge transfer rate during reaction processes, but also endows more redox reactions, as verified by first-principle calcns. These merits can help the fabricated δ-MnO2-x-2.0 cathode to present a large specific capacity of 551.8 mAh g-1 at 0.5 A g-1, high-rate capability of 262.2 mAh g-1 at 10 A g-1 and an excellent cycle lifespan (83% of capacity retention after 1500 cycles), which is far superior to those of the other metal compd. cathodes. In addn., the charge/discharge mechanism of the δ-MnO2-x-2.0 cathode has also been elaborated through ex situ techniques. This work opens up a new pathway for constructing the next-generation high-performance ZIBs cathode materials.
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  32. 32
    Shimizu, K.; Shchukarev, A.; Boily, J.-F. X-ray Photoelectron Spectroscopy of Fast-Frozen Hematite Colloids in Aqueous Solutions. 3. Stabilization of Ammonium Species by Surface (Hydr)oxo Groups. J. Phys. Chem. C 2011, 115 (14), 6796– 6801,  DOI: 10.1021/jp2002035
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    32
    x-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. Part 3. Stabilization of ammonium species by surface (hydr)oxo groups
    Shimizu, Kenichi; Shchukarev, Andrei; Boily, Jean-Francois
    Journal of Physical Chemistry C (2011), 115 (14), 6796-6801CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The speciation of ammonium at the hematite/water interface was probed by cryogenic XPS. Wet pastes of colloidal hematite spheroids equilibrated in aq. solns. of 50 mM NH4Cl exhibit distinctive pH-sensitive N 1s peaks for both NH4+ (401.7 eV) and NH3 (400.1 eV), yet total N/Fe ratios remain relatively invariant (0.029 ± 0.006) throughout the pH 2.2-10.5 range. Both NH4+ and NH3 species coexist throughout most of the tested pH range. NH4+ is most likely stabilized at the interface by H bonding with surface (hydr)oxo groups. A cationic sorption edge for NH3 is driven by proton abstraction of NH4+ by (hydr)oxo groups, forming surface complexes of the type Fe-OH···NH3. These interactions shift the NH4+/NH3 equil. from pKa = 9.3 in water to 8.4 at the interface. Removal of excess water by vacuum dehydration induces, on the other hand, formation of NH2 directly bound to surface Fe atoms. These results underscore distinct ammonium species in contact with mineral surfaces and should be considered in understanding environmental and catalytic reactions in this medium.
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    Šetka, M.; Calavia, R.; Vojkůvka, L. Raman and XPS studies of ammonia sensitive polypyrrole nanorods and nanoparticles. Sci. Rep. 2019, 9 (1), 8465  DOI: 10.1038/s41598-019-44900-1
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    Raman and XPS studies of ammonia sensitive polypyrrole nanorods and nanoparticles
    Setka Milena; Drbohlavova Jana; Vallejos Stella; Calavia Raul; Llobet Eduard; Vojkuvka Lukas; Drbohlavova Jana; Vallejos Stella
    Scientific reports (2019), 9 (1), 8465 ISSN:.
    Polypyrrole (PPy) nanorods (NRs) and nanoparticles (NPs) are synthesized via electrochemical and chemical methods, respectively, and tested upon ammonia exposure using Raman and X-ray photoelectron spectroscopy (XPS). Characterization of both nanomaterials via Raman spectroscopy demonstrates the formation of PPy, displaying vibration bands consistent with the literature. Additionally, XPS reveals the presence of neutral PPy species as major components in PPy NRs and PPy NPs, and other species including polarons and bipolarons. Raman and XPS analysis after ammonia exposure show changes in the physical/chemical properties of PPy, confirming the potential of both samples for ammonia sensing. Results demonstrate that the electrochemically synthesized NRs involve both proton and electron transfer mechanisms during ammonia exposure, as opposed to the chemically synthesized NPs, which show a mechanism dominated by electron transfer. Thus, the different detection mechanisms in PPy NRs and PPy NPs appear to be connected to the particular morphological and chemical composition of each film. These results contribute to elucidate the mechanisms involved in ammonia detection and the influence of the synthesis routes and the physical/chemical characteristics of PPy.
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    Sidey, V. On the effective ionic radii for ammonium. Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater. 2016, 72 (4), 626– 633,  DOI: 10.1107/S2052520616008064
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    On the effective ionic radii for ammonium
    Sidey, Vasyl
    Acta Crystallographica, Section B: Structural Science, Crystal Engineering and Materials (2016), 72 (4), 626-633CODEN: ACSBDA; ISSN:2052-5206. (International Union of Crystallography)
    A set of effective ionic radii corresponding to different coordination nos. (CNs) and compatible with the radii system by Shannon [Acta Cryst. (1976), A32, 751-767] has been derived for ammonium: 1.40 Å (CN = IV), 1.48 Å (CN = VI), 1.54 Å (CN = VIII) and 1.67 Å (CN = XII). The bond-valence parameters r0 = 2.3433 Å and B = 0.262 Å have been detd. for ammonium-fluorine bonds.
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    Kubota, S.; Ozaki, S.; Onishi, J. Selectivity on Ion Transport across Bilayer Lipid Membranes in the Presence of Gramicidin A. Anal. Sci. 2009, 25 (2), 189– 193,  DOI: 10.2116/analsci.25.189
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    Selectivity on ion transport across bilayer lipid membranes in the presence of gramicidin A
    Kubota, Shintaro; Ozaki, Shunsuke; Onishi, Jun; Kano, Kenji; Shirai, Osamu
    Analytical Sciences (2009), 25 (2), 189-193CODEN: ANSCEN; ISSN:0910-6340. (Japan Society for Analytical Chemistry)
    Ion transport from one aq. (W1) to another (W2) across bilayer lipid membranes (BLM) contg. gramicidin A (GA) was investigated by recording current fluctuations, when various alkali metal chlorides and potassium salts were used as supporting electrolytes. The magnitude of the single-channel current at a given membrane potential depended on not only the cationic species, but also on the anionic species, and then it decreased with an increase in the diam. of the anion when the diam. of the anion was larger than the pore size of the GA channel. The baseline of the recording current, however, increased with an increase in the diam. of the anion, and its height depended on the concn. of GA in the BLM. The results indicate that GA serves as not only a channel-forming compd., but also as a carrier compd. in the BLM.
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    Chen, Q.; Jin, J.; Song, M. High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors. Adv. Mater. 2022, 34 (8), 2107992  DOI: 10.1002/adma.202107992
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    High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors
    Chen, Qiang; Jin, Jialun; Song, Mengda; Zhang, Xiangyong; Li, Hang; Zhang, Jianli; Hou, Guangya; Tang, Yiping; Mai, Liqiang; Zhou, Liang
    Advanced Materials (Weinheim, Germany) (2022), 34 (8), 2107992CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The development of novel electrochem. energy storage devices is a grand challenge. Here, an aq. ammonium-ion hybrid supercapacitor (A-HSC), consisting of a layered δ-MnO2 based cathode, an activated carbon cloth anode, and an aq. (NH4)2SO4 electrolyte is developed. The aq. A-HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm-2 with a wide voltage window of 2.0 V. An amenable peak areal energy d. (861.2μWh cm-2) and a decent capacitance retention (72.2% after 5000 cycles) are also achieved, surpassing traditional metal-ion hybrid supercapacitors. Ex situ characterizations reveal that NH4+ intercalation/deintercalation in the layered δ-MnO2 is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochem. energy storage.
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    Yuan, A.; Wang, X.; Wang, Y. Textural and capacitive characteristics of MnO2 nanocrystals derived from a novel solid-reaction route. Electrochim. Acta 2009, 54 (3), 1021– 1026,  DOI: 10.1016/j.electacta.2008.08.057
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    Textural and capacitive characteristics of MnO2 nanocrystals derived from a novel solid-reaction route
    Yuan, Anbao; Wang, Xiuling; Wang, Yuqin; Hu, Jie
    Electrochimica Acta (2009), 54 (3), 1021-1026CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)
    Nanostructured Mn dioxide (MnO2) materials were synthesized via a novel room-temp. solid-reaction route starting with Mn(OAc)2·4H2O and (NH4)2C2O4·H2O raw materials. In brief, the various MnO2 materials were obtained by air-calcination (oxidn. decompn.) of the MnC2O4 precursor at different temps. followed by acid-treatment in 2 M H2SO4 soln. The influence of calcination temp. on the structural characteristics and capacitive properties in 1 M LiOH electrolyte of the MnO2 materials were studied by XRD, IR spectrum (IR), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) surface area anal., cyclic voltammetry, a.c. impedance and galvanostatic charge/discharge electrochem. methods. Exptl. results showed that calcination temp. has a significant influence on the textural and capacitive characteristics of the products. The MnO2 material obtained at the calcination temp. of 300° followed by acid-treatment belongs to nano-scale column-like (or needle-like) γ,α-type MnO2 misch crystals. While, the MnO2 materials obtained at the calcination temps. of 400, 500, and 600° followed by acid-treatment, resp., belong to γ-type MnO2 with the morphol. of aggregates of crystallites. The γ,α-MnO2 derived from calcination temp. of 300° exhibited a initial specific capacitance lower than that of the γ-MnO2 derived from the elevated temps., but presented a better high-rate charge/discharge cyclability.
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    Adomkevicius, A.; Cabo-Fernandez, L.; Wu, T. H. Na0.35MnO2 as an ionic conductor with randomly distributed nano-sized layers. J. Mater. Chem. A 2017, 5 (20), 10021– 10026,  DOI: 10.1039/C7TA02913F
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    Liu, L.; Su, L.; Lu, Y. The Origin of Electrochemical Actuation of MnO2/Ni Bilayer Film Derived by Redox Pseudocapacitive Process. Adv. Funct. Mater. 2019, 29 (8), 1806778  DOI: 10.1002/adfm.201806778
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    Li, Y.; Li, X.; Duan, H. Aerogel-structured MnO2 cathode assembled by defect-rich ultrathin nanosheets for zinc-ion batteries. Chem. Eng. J. 2022, 441, 136008  DOI: 10.1016/j.cej.2022.136008
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    Aerogel-structured MnO2 cathode assembled by defect-rich ultrathin nanosheets for zinc-ion batteries
    Li, Yang; Li, Xu; Duan, Huan; Xie, Shiyin; Dai, Ruyu; Rong, Jianhua; Kang, Feiyu; Dong, Liubing
    Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 441 (), 136008CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Rechargeable MnO2//Zn zinc-ion batteries (ZIBs) gain increasing attention as prospective candidates for large-scale energy storage applications, but MnO2 cathode materials are afflicted by intrinsic low elec. cond., sluggish Zn2+ diffusion kinetics and unstable crystal structure during Zn2+ insertion/extn. Herein, we report the scalable synthesis of an aerogel-structured MnO2 (A-MnO2) assembled by defect-rich ultrathin nanosheets for ZIBs. For the A-MnO2, V doping and its induced oxygen vacancies manipulate electronic structure to enhance elec. cond. and decrease Zn2+ diffusion energy barrier, and meanwhile, the ultrathin nanosheets-assembled aerogel structure favors the exposure of more electrochem. active sites and the shortening of ion diffusion distance. As a consequence, the A-MnO2 is endowed with markedly boosted electrochem. kinetics and thus superior electrochem. performance than defect-free MnO2 nanorod counterpart. Furthermore, flexible ZIB devices with both impressive flexibility and outstanding electrochem. properties can be realized using the A-MnO2 cathode material. This work is expected to promote the practical application of MnO2//Zn ZIBs.
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    Cui, G.; Zeng, Y.; Wu, J. Synthesis of Nitrogen-Doped KMn8O16 with Oxygen Vacancy for Stable Zinc-Ion Batteries. Adv. Sci. 2022, 9 (10), 2106067  DOI: 10.1002/advs.202106067
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  • Abstract

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    Figure 1

    Figure 1. Powder characterization results: (A) TEM image of K-MnO2, (B) Mn EDS mapping of K-MnO2, (C) K EDS mapping of K-MnO2, (D) TEM image of NH4-MnO2, (E) Mn EDS mapping of NH4-MnO2, (F) K EDS mapping of NH4-MnO2, (G) N EDS mapping of NH4-MnO2, (H) zoom-in TEM image of K-MnO2, (I) zoom-in TEM image of NH4-MnO2, (J) XRD results of K-MnO2 and NH4-MnO2, (K) FT-IR results, (L) structure of the synthesized NH4-MnO2, (M) deconvoluted Raman spectra of K-MnO2, and (N) deconvoluted Raman spectra of NH4-MnO2.

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    Figure 2

    Figure 2. Results of electrochemical performance: (A) GCD results at the first cycle, (B) rate capability, voltage profile vs specific capacity using GCD of (C) K-MnO2 and (D) NH4-MnO2, (E) CV results, (F) GITT results, and (G) cyclability results.

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    Figure 3

    Figure 3. Charge-storage mechanism determination results: (A) synchrotron XRD results of K-MnO2 and NH4-MnO2 at charge/discharge state (after fifth cycle), (B, C) XANES spectra measured via in situ XAS technique, (D, E) density functional theory (DFT)-optimized models and plots of the partial density of states (PDOS), (F) zoom-in image of the XANES results, (G) in-situ EXAFS of K-MnO2 upon discharging, (H) in-situ EXAFS of NH4-MnO2 upon discharging, (I) schema of the stabilization of MnO2 using NH4+ cations, and (J) EXAFS of K-MnO2 and NH4-MnO2 at a discharged state.

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      There is no corresponding record for this reference.
    4. 4
      Chen, S.; Wang, H.; Zhu, M. Revitalizing zinc-ion batteries with advanced zinc anode design. Nanoscale Horiz. 2022, 8 (1), 29– 54,  DOI: 10.1039/D2NH00354F
      There is no corresponding record for this reference.
    5. 5
      Jia, S.; Li, L.; Shi, Y. Recent development of manganese dioxide-based materials as zinc-ion battery cathode. Nanoscale 2024, 16 (4), 1539– 1576,  DOI: 10.1039/D3NR04996E
      There is no corresponding record for this reference.
    6. 6
      Wen, Q.; Fu, H.; Cui, R. d. Recent advances in interfacial modification of zinc anode for aqueous rechargeable zinc ion batteries. J. Energy Chem. 2023, 83, 287– 303,  DOI: 10.1016/j.jechem.2023.03.059
      6
      Recent advances in interfacial modification of zinc anode for aqueous rechargeable zinc ion batteries
      Wen, Qing; Fu, Hao; Cui, Ru-de; Chen, He-Zhang; Ji, Rui-Han; Tang, Lin-Bo; Yan, Cheng; Mao, Jing; Dai, Ke-Hua; Zhang, Xia-Hui; Zheng, Jun-Chao
      Journal of Energy Chemistry (2023), 83 (), 287-303CODEN: JECOFG; ISSN:2095-4956. (Science Press)
      A review. To tackle energy crisis and achieve sustainable development, aq. rechargeable zinc ion batteries have gained widespread attention in large-scale energy storage for their low cost, high safety, high theor. capacity, and environmental compatibility in recent years. However, zinc anode in aq. zinc ion batteries is still facing several challenges such as dendrite growth and side reactions (e.g., hydrogen evolution), which cause poor reversibility and the failure of batteries. To address these issues, interfacial modification of Zn anodes has received great attention by tuning the interaction between the anode and the electrolyte. Herein, we present recent advances in the interfacial modification of zinc anode in this review. Besides, the challenges of reported approaches of interfacial modification are also discussed. Finally, we provide an outlook for the exploration of novel zinc anode for aq. zinc ion batteries. We hope that this review will be helpful in designing and fabricating dendrite-free and hydrogen-evolution-free Zn anodes and promoting the practical application of aq. rechargeable zinc ion batteries.
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    7. 7
      Gopalakrishnan, M.; Ganesan, S.; Nguyen, M. T. Critical roles of metal–organic frameworks in improving the Zn anode in aqueous zinc-ion batteries. Chem. Eng. J. 2023, 457, 141334  DOI: 10.1016/j.cej.2023.141334
      There is no corresponding record for this reference.
    8. 8
      Nie, C.; Wang, G.; Wang, D. Recent Progress on Zn Anodes for Advanced Aqueous Zinc-Ion Batteries. Adv. Energy Mater. 2023, 13 (28), 2300606  DOI: 10.1002/aenm.202300606
      8
      Recent Progress on Zn Anodes for Advanced Aqueous Zinc-Ion Batteries
      Nie, Chuanhao; Wang, Gulian; Wang, Dongdong; Wang, Mingyue; Gao, Xinran; Bai, Zhongchao; Wang, Nana; Yang, Jian; Xing, Zheng; Dou, Shixue
      Advanced Energy Materials (2023), 13 (28), 2300606CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell)
      A review. Aq. Zn-ion batteries (AZIBs) have attracted much attention due to their excellent safety, cost-effectiveness, and eco-friendliness thereby being considered as one of the most promising candidates for large-scale energy storage. Zn metal anodes with a high gravimetric/volumetric capacity are indispensable for advanced AZIBs. However, pristine Zn metal anodes encounter severe challenges in achieving adequate cycling stability, including dendrite growth, hydrogen evolution reaction, self-corrosion, and byproduct formation. Because all these reactions are closely related to the electrolyte/Zn interface, the subtle interface engineering is important. Many strategies targeted to the interface engineering have been developed. In this review, a timely update on these strategies and perspectives are summarized, esp. focusing on the controllable synthesis of Zn, Zn surface engineering, electrolyte formulation, and separator design. Furthermore, the corresponding internal principles of these strategies are clarified, which is helpful to help seek for new strategies. Finally, the challenges and perspectives for the future development of practical AZIBs are discussed, including the conducting of in advanced in situ testing, unification of battery models, some boundary issues, etc. This review is expected to guide the future development and provi beacon light direction for aq. zinc ion batteries.
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    9. 9
      Ma, L.; Chen, S.; Li, N. Hydrogen-Free and Dendrite-Free All-Solid-State Zn-Ion Batteries. Adv. Mater. 2020, 32 (14), 1908121  DOI: 10.1002/adma.201908121
      9
      Hydrogen-Free and Dendrite-Free All-Solid-State Zn-Ion Batteries
      Ma, Longtao; Chen, Shengmei; Li, Na; Liu, Zhuoxin; Tang, Zijie; Zapien, Juan Antonio; Chen, Shimou; Fan, Jun; Zhi, Chunyi
      Advanced Materials (Weinheim, Germany) (2020), 32 (14), 1908121CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      An ionic-liq.-based Zn salt electrolyte is demonstrated to be an effective route to solve both the side-reaction of the hydrogen evolution reaction (HER) and Zn-dendrite growth in Zn-ion batteries. The developed electrolyte enables hydrogen-free, dendrite-free Zn plating/stripping over 1500 h cycle (3000 cycles) at 2 mA cm-2 with nearly 100% coulombic efficiency. Meanwhile, the oxygen-induced corrosion and passivation are also effectively suppressed. These features bring Zn-ion batteries an unprecedented long lifespan over 40 000 cycles at 4 A g-1 and high voltage of 2.05 V with a cobalt hexacyanoferrate cathode. Furthermore, a 28.6μm thick solid polymer electrolyte of a poly(vinylidene fluoride-hexafluoropropylene) film filled with poly(ethylene oxide)/ionic-liq.-based Zn salt is constructed to build an all-solid-state Zn-ion battery. The all-solid-state Zn-ion batteries show excellent cycling performance of 30 000 cycles at 2 A g-1 at room temp. and withstand high temp. ≤ 70°, low temp. to -20°, as well as abuse test of bending deformation up to 150° for 100 cycles and eight times cutting. This is the first demonstration of an all-solid-state Zn-ion battery based on a newly developed electrolyte, which meanwhile solves the deep-seated hydrogen evolution and dendrite growth problem in traditional Zn-ion batteries.
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    10. 10
      Kao-ian, W.; Mohamad, A. A.; Liu, W. Stability Enhancement of Zinc-Ion Batteries Using Non-Aqueous Electrolytes. Batteries Supercaps 2022, 5 (5), e202100361  DOI: 10.1002/batt.202100361
      There is no corresponding record for this reference.
    11. 11
      Etman, A. S.; Carboni, M.; Sun, J. Acetonitrile-Based Electrolytes for Rechargeable Zinc Batteries. Energy Technol. 2020, 8 (9), 2000358  DOI: 10.1002/ente.202000358
      There is no corresponding record for this reference.
    12. 12
      Han, S.-D.; Kim, S.; Li, D. Mechanism of Zn Insertion into Nanostructured δ-MnO2: A Nonaqueous Rechargeable Zn Metal Battery. Chem. Mater. 2017, 29 (11), 4874– 4884,  DOI: 10.1021/acs.chemmater.7b00852
      12
      Mechanism of Zn Insertion into Nanostructured δ-MnO2: A Nonaqueous Rechargeable Zn Metal Battery
      Han, Sang-Don; Kim, Soojeong; Li, Dongguo; Petkov, Valeri; Yoo, Hyun Deog; Phillips, Patrick J.; Wang, Hao; Kim, Jae Jin; More, Karren L.; Key, Baris; Klie, Robert F.; Cabana, Jordi; Stamenkovic, Vojislav R.; Fister, Timothy T.; Markovic, Nenad M.; Burrell, Anthony K.; Tepavcevic, Sanja; Vaughey, John T.
      Chemistry of Materials (2017), 29 (11), 4874-4884CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Unlike the more established lithium-ion based energy storage chemistries, the complex intercalation chem. of multivalent cations in a host lattice is not well understood, esp. the relationship between the intercalating species soln. chem. and the prevalence and type of side reactions. Among multivalent metals, a promising model system can be based on nonaq. Zn2+ ion chem. Several examples of these systems support the use of a Zn metal anode, and reversible intercalation cathodes have been reported. This study utilizes a combination of anal. tools to probe the chem. of a nanostructured δ-MnO2 cathode in assocn. with a nonaq. acetonitrile-Zn(TFSI)2 electrolyte and a Zn metal anode. As many of the issues related to understanding a multivalent battery relate to the electrolyte-electrode interface, the high surface area of a nanostructured cathode provides a significant interface between the electrolyte and cathode host that maximizes the spectroscopic signal of any side reactions or minor mechanistic pathways. Numerous factors affecting capacity fade and issues assocd. with the second phase formation including Mn dissoln. in heavily cycled Zn/δ-MnO2 cells are presented including dramatic mechanistic differences in the storage mechanism of this couple when compared to similar aq. electrolytes are noted.
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    13. 13
      Shin, J.; Choi, D. S.; Lee, H. J. Hydrated Intercalation for High-Performance Aqueous Zinc Ion Batteries. Adv. Energy Mater. 2019, 9 (14), 1900083  DOI: 10.1002/aenm.201900083
      There is no corresponding record for this reference.
    14. 14
      Kundu, D.; Vajargah, S. H.; Wan, L. Aqueous vs. nonaqueous Zn-ion batteries: consequences of the desolvation penalty at the interface. Energy Environ. Sci. 2018, 11 (4), 881– 892,  DOI: 10.1039/C8EE00378E
      14
      Aqueous vs. nonaqueous Zn-ion batteries: consequences of the desolvation penalty at the interface
      Kundu, Dipan; Hosseini Vajargah, Shahrzad; Wan, Liwen; Adams, Brian; Prendergast, David; Nazar, Linda F.
      Energy & Environmental Science (2018), 11 (4), 881-892CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      Zinc ion batteries using metallic zinc as the neg. electrode have gained considerable interest for electrochem. energy storage, whose development is crucial for the adoption of renewable energy technologies, as zinc has a very high volumetric capacity (5845 mA h cm-3), is inexpensive and compatible with aq. electrolytes. However, the divalent charge of zinc ions, which restricts the choice of host material due to hindered solid-state diffusion, can also pose a problem for interfacial charge transfer. Here, we report our findings on reversible intercalation of up to two Zn2+ ions in layered V3O7·H2O. This material exhibits very high capacity and power (375 mA h g-1 at a 1C rate, and 275 mA h g-1 at an 8C rate) in an aq. electrolyte compared to a very low capacity and slow rate capabilities in a nonaq. medium. Operando XRD studies, together with impedance anal., reveal solid soln. behavior assocd. with Zn2+-ion diffusion within a water monolayer in the interlayer gap in both systems, but very sluggish interfacial charge transfer in the nonaq. electrolyte. This points to desolvation at the interface as a major factor in dictating the kinetics. Temp. dependent impedance studies show high activation energies assocd. with the nonaq. charge transfer process, identifying the origin of poor electrochem. performance.
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    15. 15
      Kao-ian, W.; Sangsawang, J.; Kidkhunthod, P. Unveiling the role of water in enhancing the performance of zinc-ion batteries using dimethyl sulfoxide electrolyte and the manganese dioxide cathode. J. Mater. Chem. A 2023, 11 (20), 10584– 10595,  DOI: 10.1039/D3TA01014G
      There is no corresponding record for this reference.
    16. 16
      Wang, R.; Boyd, S.; Bonnesen, P. V. Effect of water in a non-aqueous electrolyte on electrochemical Mg2+ insertion into WO3. J. Power Sources 2020, 477, 229015  DOI: 10.1016/j.jpowsour.2020.229015
      16
      Effect of water in a non-aqueous electrolyte on electrochemical Mg2+ insertion into WO3
      Wang, Ruocun; Boyd, Shelby; Bonnesen, Peter V.; Augustyn, Veronica
      Journal of Power Sources (2020), 477 (), 229015CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      Magnesium batteries are promising candidates for beyond lithium-ion batteries, but face several challenges including the need for solid state materials capable of reversible Mg2+ insertion. Of fundamental interest is the need to understand and improve the Mg2+ insertion kinetics of oxide-based cathode materials in non-aq. electrolytes. The addn. of water in non-aq. electrolytes has been shown to improve the kinetics of Mg2+ insertion, but the mechanism and the effect of water concn. are still under debate. We investigate the systematic addn. of water into a non-aq. Mg electrolyte and its effect on Mg2+ insertion into WO3. We find that the addn. of water leads to improvement in the Mg2+ insertion kinetics up to 6[H2O] : [Mg]2+. We utilize electrochem. coupled to ex situ characterization to systematically explore four potential mechanisms for the electrochem. behavior: water co-insertion, proton (co)insertion, beneficial interphase formation, and water-enhanced surface diffusion. Based on these studies, we find that while proton co-insertion likely occurs, the dominant inserting species is Mg2+, and propose that the kinetic improvement upon water addn. is due to enhanced surface diffusion of ions.
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    17. 17
      Verma, V.; Kumar, S.; Manalastas, W. Layered VOPO4 as a Cathode Material for Rechargeable Zinc-Ion Battery: Effect of Polypyrrole Intercalation in the Host and Water Concentration in the Electrolyte. ACS Appl. Energy Mater. 2019, 2 (12), 8667– 8674,  DOI: 10.1021/acsaem.9b01632
      There is no corresponding record for this reference.
    18. 18
      Han, D.; Cui, C.; Zhang, K. A non-flammable hydrous organic electrolyte for sustainable zinc batteries. Nat. Sustain. 2022, 5 (3), 205– 213,  DOI: 10.1038/s41893-021-00800-9
      There is no corresponding record for this reference.
    19. 19
      Setiawan, D.; Lee, H.; Kwak, H. H. Bi-layered calcium vanadium oxide as a cathode material for wet organic electrolyte-based rechargeable Zn-ion batteries. J. Energy Storage 2023, 72, 108497  DOI: 10.1016/j.est.2023.108497
      There is no corresponding record for this reference.
    20. 20
      Asl, H. Y.; Sharma, S.; Manthiram, A. The critical effect of water content in the electrolyte on the reversible electrochemical performance of Zn–VPO4F cells. J. Mater. Chem. A 2020, 8 (17), 8262– 8267,  DOI: 10.1039/D0TA01622E
      There is no corresponding record for this reference.
    21. 21
      Li, H. A high-performance MnO2 cathode doped with group VIII metal for aqueous Zn-ion batteries: In-situ X-Ray diffraction study on Zn2+ storage mechanism. J. Power Sources 2022, 527, 231198  DOI: 10.1016/j.jpowsour.2022.231198
      There is no corresponding record for this reference.
    22. 22
      Zhang, Y.; Deng, S.; Li, Y. Anchoring MnO2 on nitrogen-doped porous carbon nanosheets as flexible arrays cathodes for advanced rechargeable Zn–MnO2 batteries. Energy Storage Mater. 2020, 29, 52– 59,  DOI: 10.1016/j.ensm.2020.04.003
      There is no corresponding record for this reference.
    23. 23
      Yao, H.; Yu, H.; Zheng, Y. Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries. Angew. Chem., Int. Ed. 2023, 62 (51), e202315257  DOI: 10.1002/anie.202315257
      23
      Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries
      Yao, Haixin; Yu, Huan; Zheng, Yaqi; Li, Nian Wu; Li, Sheng; Luan, Deyan; Lou, Xiong Wen; Yu, Le
      Angewandte Chemie, International Edition (2023), 62 (51), e202315257CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Layered manganese dioxide is a promising cathode candidate for aq. Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic cond. and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K+-intercalated δ-MnO2 nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K+ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochem. properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.
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    24. 24
      Sun, T.; Zheng, S.; Nian, Q. Hydrogen Bond Shielding Effect for High-Performance Aqueous Zinc Ion Batteries. Small 2022, 18 (12), 2107115  DOI: 10.1002/smll.202107115
      There is no corresponding record for this reference.
    25. 25
      Fu, Y.; Jia, C.; Chen, Z. Modulating residual ammonium in MnO2 for high-rate aqueous zinc-ion batteries. Nanoscale 2022, 14 (8), 3242– 3249,  DOI: 10.1039/D1NR07406G
      There is no corresponding record for this reference.
    26. 26
      Liu, Y.; Wei, J.; Tian, Y. The structure–property relationship of manganese oxides: highly efficient removal of methyl orange from aqueous solution. J. Mater. Chem. A 2015, 3 (37), 19000– 19010,  DOI: 10.1039/C5TA05507E
      26
      The structure-property relationship of manganese oxides: highly efficient removal of methyl orange from aqueous solution
      Liu, Yan; Wei, Jie; Tian, Yaxi; Yan, Shiqiang
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (37), 19000-19010CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Mn oxides of various crystal structures (α-, β-, γ- and δ-MnO2, Mn2O3, Mn3O4 and amorphous) were synthesized by facile methods. The adsorption capacities for Methyl orange of these materials were studied and the resulting materials were characterized by different techniques, such as SEM, XRD and BET surface area measurements. The adsorption capacities were strongly dependent on the crystallog. structures and morphologies, and followed the order of A-MnO2 > Mn2O3 > Mn3O4 > α-MnO2 nanowires > β-MnO2 > γ-MnO2 > α-MnO2 nanotubes >δ-MnO2, while the adsorption properties could be greatly improved by increasing the surface area and pore properties of the adsorbents. A-MnO2 was the most effective adsorbent among the other materials and the adsorption process was systematically studied. The adsorption kinetics data closely followed the pseudo-2nd-order kinetic model and the results obtained from the intraparticle diffusion model indicated that the overall process was jointly influenced by external mass transfer and intra-particle diffusion. The max. adsorption capacity detd. from the Langmuir isotherm model was 1488.7 mg/g. Thermodn. analyses revealed that the adsorption of MO onto A-MnO2 was spontaneous and exothermic, and the phys. adsorption mechanisms including electrostatic interactions played a dominant role in the adsorption process between MO and A-MnO2. These combined results indicated that A-MnO2 is an efficient adsorbent for the removal of MO from wastewater.
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    27. 27
      Kao-ian, W.; Nguyen, M.; Yonezawa, T. Highly stable rechargeable zinc-ion battery using dimethyl sulfoxide electrolyte. Mater. Today Energy 2021, 21, 100738  DOI: 10.1016/j.mtener.2021.100738
      27
      Highly stable rechargeable zinc-ion battery using dimethyl sulfoxide electrolyte
      Kao-ian, W.; Nguyen, M. T.; Yonezawa, T.; Pornprasertsuk, R.; Qin, J.; Siwamogsatham, S.; Kheawhom, S.
      Materials Today Energy (2021), 21 (), 100738CODEN: MTEACH; ISSN:2468-6069. (Elsevier Ltd.)
      Due to their high safety, low cost, eco-friendliness, and impressive electrochem. performance, rechargeable zinc-ion batteries (ZIBs) show great potential as elec. energy storage devices for large-scale applications. Nonetheless, recently developed ZIBs still suffer from low cycling stability and high capacity fading. Such shortcomings are caused by the reversibility of both zinc (Zn) and the cathode host material, as well as hydrogen evolution in aq. electrolytes, which are naturally protic solvents. Herein, DMSO (DMSO), a polar aprotic solvent, is examd. as an electrolyte for a ZIB. Zn stripping/plating in DMSO-based electrolytes shows excellent reversibility and dendrite-free morphol. During charging and resting modes, hydrogen evolution is effectively inhibited. Insertion/extn. of Zn ions in DMSO-based electrolytes into delta-type manganese dioxide (δ-MnO2) demonstrates high stability, achieving a decent initial capacity of 159 mAh/g at 50 mA/g and a nominal discharge voltage of 1.15 V. At 100 mA/g charge/discharge cycling, the ZIB, having the DMSO-based electrolyte, can pass 1000 cycles, displaying a capacity retention of 60%. Overall, the improved performance of ZIBs can be attained using DMSO-based electrolytes. Results pave the way towards the practical application of ZIBs.
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    28. 28
      Wang, M.; Yagi, S. Layered birnessite MnO2 with enlarged interlayer spacing for fast Mg-ion storage. J. Alloys Compd. 2020, 820, 153135  DOI: 10.1016/j.jallcom.2019.153135
      28
      Layered birnessite MnO2 with enlarged interlayer spacing for fast Mg-ion storage
      Wang, Mengqiao; Yagi, Shunsuke
      Journal of Alloys and Compounds (2020), 820 (), 153135CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      To identify appropriate electrode active materials for application in Mg batteries, the Mg2+ storage ability of birnessite MnO2 with different interlayer spacings was investigated. The changes in the redox peak position in the cyclic voltammograms of birnessite MnO2 with different interlayer spacings confirmed the intercalation/deintercalation reactions of Mg2+ ions to/from the interlayers of layered birnessite MnO2 and their surface adsorption. The role of water mols. in the charge/discharge processes was also investigated using an electrochem. quartz crystal microbalance, and a plausible reaction mechanism was proposed. It was found that the specific capacity nearly doubled, from 58.6 to 110.8 mAh g-1, at 1 C when the interlayer spacing of birnessite MnO2 was expanded, from 0.70 to 0.97 nm, by altering the original intercalated ions. The rate capability was also significantly improved by expanding the interlayer spacing. Such excellent discharge-charge properties were ascribed to the broader diffusion channel, which enabled easier Mg2+ diffusion. The strategy reported herein provides an efficient method to fabricate outstanding active materials for application in Mg batteries and a new strategy to develop active materials for other energy storage devices.
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    29. 29
      Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 2005, 12 (4), 537– 541,  DOI: 10.1107/S0909049505012719
      29
      ATHENA, ARTEMIS, HEPHAESTUS: data analysis for x-ray absorption spectroscopy using IFEFFIT
      Ravel, B.; Newville, M.
      Journal of Synchrotron Radiation (2005), 12 (4), 537-541CODEN: JSYRES; ISSN:0909-0495. (Blackwell Publishing Ltd.)
      A software package for the anal. of x-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data anal. using theor. stds. from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of at. absorption data. These programs enable high-quality data anal. that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
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    30. 30
      Misnon, I. I.; Aziz, R. A.; Zain, N. K. M. High performance MnO2 nanoflower electrode and the relationship between solvated ion size and specific capacitance in highly conductive electrolytes. Mater. Res. Bull. 2014, 57, 221– 230,  DOI: 10.1016/j.materresbull.2014.05.044
      30
      High performance MnO2 nanoflower electrode and the relationship between solvated ion size and specific capacitance in highly conductive electrolytes
      Misnon, Izan Izwan; Aziz, Radhiyah Abd; Zain, Nurul Khairiyyah Mohd; Vidhyadharan, Baiju; Krishnan, Syam G.; Jose, Rajan
      Materials Research Bulletin (2014), 57 (), 221-230CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
      Flower shaped birnessite type manganese oxide (δ-MnO2) nanostructures are synthesized using a simple hydrothermal process with an aim to fabricate high performance supercapacitors for energy storage electrode. The studies reveal that layered δ-MnO2 had a basal plane spacing of ∼0.73 nm and are composed of thin nanosheets of thickness ∼23 nm. A detailed investigation is undertaken to draw a relationship between the solvated ion size of alk. electrolytes (LiOH, NaOH and KOH) and pore size in the electrode material favoring high specific capacitance and faster electrode kinetics. The present work not only develops a high performance supercapacitive material but also identifies that by suitably tuning the sizes of solvated ion and the pores, supercapacitive behavior of a single material system can be tailored.
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    31. 31
      Wang, Y.; Zhang, Y.; Gao, G. Effectively Modulating Oxygen Vacancies in Flower-Like δ-MnO2 Nanostructures for Large Capacity and High-Rate Zinc-Ion Storage. Nano-Micro Lett. 2023, 15 (1), 219,  DOI: 10.1007/s40820-023-01194-3
      31
      Effectively Modulating Oxygen Vacancies in Flower-Like δ-MnO2 Nanostructures for Large Capacity and High-Rate Zinc-Ion Storage
      Wang, Yiwei; Zhang, Yuxiao; Gao, Ge; Fan, Yawen; Wang, Ruoxin; Feng, Jie; Yang, Lina; Meng, Alan; Zhao, Jian; Li, Zhenjiang
      Nano-Micro Letters (2023), 15 (1), 219CODEN: NLAEBV; ISSN:2150-5551. (Springer International Publishing AG)
      In recent years, manganese-based oxides as an advanced class of cathode materials for zinc-ion batteries (ZIBs) have attracted a great deal of attentions from numerous researchers. However, their slow reaction kinetics, limited active sites and poor elec. cond. inevitably give rise to the severe performance degrdn. To solve these problems, herein, we introduce abundant oxygen vacancies into the flower-like δ-MnO2 nanostructure and effectively modulate the vacancy defects to reach the optimal level (δ-MnO2-x-2.0). The smart design intrinsically tunes the electronic structure, guarantees ion chemisorption-desorption equil. and increases the electroactive sites, which not only effectively accelerates charge transfer rate during reaction processes, but also endows more redox reactions, as verified by first-principle calcns. These merits can help the fabricated δ-MnO2-x-2.0 cathode to present a large specific capacity of 551.8 mAh g-1 at 0.5 A g-1, high-rate capability of 262.2 mAh g-1 at 10 A g-1 and an excellent cycle lifespan (83% of capacity retention after 1500 cycles), which is far superior to those of the other metal compd. cathodes. In addn., the charge/discharge mechanism of the δ-MnO2-x-2.0 cathode has also been elaborated through ex situ techniques. This work opens up a new pathway for constructing the next-generation high-performance ZIBs cathode materials.
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    32. 32
      Shimizu, K.; Shchukarev, A.; Boily, J.-F. X-ray Photoelectron Spectroscopy of Fast-Frozen Hematite Colloids in Aqueous Solutions. 3. Stabilization of Ammonium Species by Surface (Hydr)oxo Groups. J. Phys. Chem. C 2011, 115 (14), 6796– 6801,  DOI: 10.1021/jp2002035
      32
      x-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. Part 3. Stabilization of ammonium species by surface (hydr)oxo groups
      Shimizu, Kenichi; Shchukarev, Andrei; Boily, Jean-Francois
      Journal of Physical Chemistry C (2011), 115 (14), 6796-6801CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The speciation of ammonium at the hematite/water interface was probed by cryogenic XPS. Wet pastes of colloidal hematite spheroids equilibrated in aq. solns. of 50 mM NH4Cl exhibit distinctive pH-sensitive N 1s peaks for both NH4+ (401.7 eV) and NH3 (400.1 eV), yet total N/Fe ratios remain relatively invariant (0.029 ± 0.006) throughout the pH 2.2-10.5 range. Both NH4+ and NH3 species coexist throughout most of the tested pH range. NH4+ is most likely stabilized at the interface by H bonding with surface (hydr)oxo groups. A cationic sorption edge for NH3 is driven by proton abstraction of NH4+ by (hydr)oxo groups, forming surface complexes of the type Fe-OH···NH3. These interactions shift the NH4+/NH3 equil. from pKa = 9.3 in water to 8.4 at the interface. Removal of excess water by vacuum dehydration induces, on the other hand, formation of NH2 directly bound to surface Fe atoms. These results underscore distinct ammonium species in contact with mineral surfaces and should be considered in understanding environmental and catalytic reactions in this medium.
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    33. 33
      Šetka, M.; Calavia, R.; Vojkůvka, L. Raman and XPS studies of ammonia sensitive polypyrrole nanorods and nanoparticles. Sci. Rep. 2019, 9 (1), 8465  DOI: 10.1038/s41598-019-44900-1
      33
      Raman and XPS studies of ammonia sensitive polypyrrole nanorods and nanoparticles
      Setka Milena; Drbohlavova Jana; Vallejos Stella; Calavia Raul; Llobet Eduard; Vojkuvka Lukas; Drbohlavova Jana; Vallejos Stella
      Scientific reports (2019), 9 (1), 8465 ISSN:.
      Polypyrrole (PPy) nanorods (NRs) and nanoparticles (NPs) are synthesized via electrochemical and chemical methods, respectively, and tested upon ammonia exposure using Raman and X-ray photoelectron spectroscopy (XPS). Characterization of both nanomaterials via Raman spectroscopy demonstrates the formation of PPy, displaying vibration bands consistent with the literature. Additionally, XPS reveals the presence of neutral PPy species as major components in PPy NRs and PPy NPs, and other species including polarons and bipolarons. Raman and XPS analysis after ammonia exposure show changes in the physical/chemical properties of PPy, confirming the potential of both samples for ammonia sensing. Results demonstrate that the electrochemically synthesized NRs involve both proton and electron transfer mechanisms during ammonia exposure, as opposed to the chemically synthesized NPs, which show a mechanism dominated by electron transfer. Thus, the different detection mechanisms in PPy NRs and PPy NPs appear to be connected to the particular morphological and chemical composition of each film. These results contribute to elucidate the mechanisms involved in ammonia detection and the influence of the synthesis routes and the physical/chemical characteristics of PPy.
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    34. 34
      Sidey, V. On the effective ionic radii for ammonium. Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater. 2016, 72 (4), 626– 633,  DOI: 10.1107/S2052520616008064
      34
      On the effective ionic radii for ammonium
      Sidey, Vasyl
      Acta Crystallographica, Section B: Structural Science, Crystal Engineering and Materials (2016), 72 (4), 626-633CODEN: ACSBDA; ISSN:2052-5206. (International Union of Crystallography)
      A set of effective ionic radii corresponding to different coordination nos. (CNs) and compatible with the radii system by Shannon [Acta Cryst. (1976), A32, 751-767] has been derived for ammonium: 1.40 Å (CN = IV), 1.48 Å (CN = VI), 1.54 Å (CN = VIII) and 1.67 Å (CN = XII). The bond-valence parameters r0 = 2.3433 Å and B = 0.262 Å have been detd. for ammonium-fluorine bonds.
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    35. 35
      Kubota, S.; Ozaki, S.; Onishi, J. Selectivity on Ion Transport across Bilayer Lipid Membranes in the Presence of Gramicidin A. Anal. Sci. 2009, 25 (2), 189– 193,  DOI: 10.2116/analsci.25.189
      35
      Selectivity on ion transport across bilayer lipid membranes in the presence of gramicidin A
      Kubota, Shintaro; Ozaki, Shunsuke; Onishi, Jun; Kano, Kenji; Shirai, Osamu
      Analytical Sciences (2009), 25 (2), 189-193CODEN: ANSCEN; ISSN:0910-6340. (Japan Society for Analytical Chemistry)
      Ion transport from one aq. (W1) to another (W2) across bilayer lipid membranes (BLM) contg. gramicidin A (GA) was investigated by recording current fluctuations, when various alkali metal chlorides and potassium salts were used as supporting electrolytes. The magnitude of the single-channel current at a given membrane potential depended on not only the cationic species, but also on the anionic species, and then it decreased with an increase in the diam. of the anion when the diam. of the anion was larger than the pore size of the GA channel. The baseline of the recording current, however, increased with an increase in the diam. of the anion, and its height depended on the concn. of GA in the BLM. The results indicate that GA serves as not only a channel-forming compd., but also as a carrier compd. in the BLM.
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    36. 36
      Chen, Q.; Jin, J.; Song, M. High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors. Adv. Mater. 2022, 34 (8), 2107992  DOI: 10.1002/adma.202107992
      36
      High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors
      Chen, Qiang; Jin, Jialun; Song, Mengda; Zhang, Xiangyong; Li, Hang; Zhang, Jianli; Hou, Guangya; Tang, Yiping; Mai, Liqiang; Zhou, Liang
      Advanced Materials (Weinheim, Germany) (2022), 34 (8), 2107992CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The development of novel electrochem. energy storage devices is a grand challenge. Here, an aq. ammonium-ion hybrid supercapacitor (A-HSC), consisting of a layered δ-MnO2 based cathode, an activated carbon cloth anode, and an aq. (NH4)2SO4 electrolyte is developed. The aq. A-HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm-2 with a wide voltage window of 2.0 V. An amenable peak areal energy d. (861.2μWh cm-2) and a decent capacitance retention (72.2% after 5000 cycles) are also achieved, surpassing traditional metal-ion hybrid supercapacitors. Ex situ characterizations reveal that NH4+ intercalation/deintercalation in the layered δ-MnO2 is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochem. energy storage.
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    37. 37
      Yuan, A.; Wang, X.; Wang, Y. Textural and capacitive characteristics of MnO2 nanocrystals derived from a novel solid-reaction route. Electrochim. Acta 2009, 54 (3), 1021– 1026,  DOI: 10.1016/j.electacta.2008.08.057
      37
      Textural and capacitive characteristics of MnO2 nanocrystals derived from a novel solid-reaction route
      Yuan, Anbao; Wang, Xiuling; Wang, Yuqin; Hu, Jie
      Electrochimica Acta (2009), 54 (3), 1021-1026CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)
      Nanostructured Mn dioxide (MnO2) materials were synthesized via a novel room-temp. solid-reaction route starting with Mn(OAc)2·4H2O and (NH4)2C2O4·H2O raw materials. In brief, the various MnO2 materials were obtained by air-calcination (oxidn. decompn.) of the MnC2O4 precursor at different temps. followed by acid-treatment in 2 M H2SO4 soln. The influence of calcination temp. on the structural characteristics and capacitive properties in 1 M LiOH electrolyte of the MnO2 materials were studied by XRD, IR spectrum (IR), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) surface area anal., cyclic voltammetry, a.c. impedance and galvanostatic charge/discharge electrochem. methods. Exptl. results showed that calcination temp. has a significant influence on the textural and capacitive characteristics of the products. The MnO2 material obtained at the calcination temp. of 300° followed by acid-treatment belongs to nano-scale column-like (or needle-like) γ,α-type MnO2 misch crystals. While, the MnO2 materials obtained at the calcination temps. of 400, 500, and 600° followed by acid-treatment, resp., belong to γ-type MnO2 with the morphol. of aggregates of crystallites. The γ,α-MnO2 derived from calcination temp. of 300° exhibited a initial specific capacitance lower than that of the γ-MnO2 derived from the elevated temps., but presented a better high-rate charge/discharge cyclability.
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    38. 38
      Adomkevicius, A.; Cabo-Fernandez, L.; Wu, T. H. Na0.35MnO2 as an ionic conductor with randomly distributed nano-sized layers. J. Mater. Chem. A 2017, 5 (20), 10021– 10026,  DOI: 10.1039/C7TA02913F
      There is no corresponding record for this reference.
    39. 39
      Liu, L.; Su, L.; Lu, Y. The Origin of Electrochemical Actuation of MnO2/Ni Bilayer Film Derived by Redox Pseudocapacitive Process. Adv. Funct. Mater. 2019, 29 (8), 1806778  DOI: 10.1002/adfm.201806778
      There is no corresponding record for this reference.
    40. 40
      Li, Y.; Li, X.; Duan, H. Aerogel-structured MnO2 cathode assembled by defect-rich ultrathin nanosheets for zinc-ion batteries. Chem. Eng. J. 2022, 441, 136008  DOI: 10.1016/j.cej.2022.136008
      40
      Aerogel-structured MnO2 cathode assembled by defect-rich ultrathin nanosheets for zinc-ion batteries
      Li, Yang; Li, Xu; Duan, Huan; Xie, Shiyin; Dai, Ruyu; Rong, Jianhua; Kang, Feiyu; Dong, Liubing
      Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 441 (), 136008CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Rechargeable MnO2//Zn zinc-ion batteries (ZIBs) gain increasing attention as prospective candidates for large-scale energy storage applications, but MnO2 cathode materials are afflicted by intrinsic low elec. cond., sluggish Zn2+ diffusion kinetics and unstable crystal structure during Zn2+ insertion/extn. Herein, we report the scalable synthesis of an aerogel-structured MnO2 (A-MnO2) assembled by defect-rich ultrathin nanosheets for ZIBs. For the A-MnO2, V doping and its induced oxygen vacancies manipulate electronic structure to enhance elec. cond. and decrease Zn2+ diffusion energy barrier, and meanwhile, the ultrathin nanosheets-assembled aerogel structure favors the exposure of more electrochem. active sites and the shortening of ion diffusion distance. As a consequence, the A-MnO2 is endowed with markedly boosted electrochem. kinetics and thus superior electrochem. performance than defect-free MnO2 nanorod counterpart. Furthermore, flexible ZIB devices with both impressive flexibility and outstanding electrochem. properties can be realized using the A-MnO2 cathode material. This work is expected to promote the practical application of MnO2//Zn ZIBs.
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    41. 41
      Cui, G.; Zeng, Y.; Wu, J. Synthesis of Nitrogen-Doped KMn8O16 with Oxygen Vacancy for Stable Zinc-Ion Batteries. Adv. Sci. 2022, 9 (10), 2106067  DOI: 10.1002/advs.202106067
      41
      Synthesis of Nitrogen-Doped KMn8O16 with Oxygen Vacancy for Stable Zinc-Ion Batteries
      Cui, Guodong; Zeng, Yinxiang; Wu, Jinfang; Guo, Yan; Gu, Xiaojun; Lou, Xiong Wen
      Advanced Science (Weinheim, Germany) (2022), 9 (10), 2106067CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The development of MnO2 as a cathode for aq. zinc-ion batteries (AZIBs) is severely limited by the low intrinsic elec. cond. and unstable crystal structure. Herein, a multifunctional modification strategy is proposed to construct N-doped KMn8O16 with abundant oxygen vacancy and large sp. surface area (named as N-KMO) through a facile one-step hydrothermal approach. The synergetic effects of N-doping, oxygen vacancy, and porous structure in N-KMO can effectively suppress the dissoln. of manganese ions, and promote ion diffusion and electron conduction. As a result, the N-KMO cathode exhibits dramatically improved stability and reaction kinetics, superior to the pristine MnO2 and MnO2 with only oxygen vacancy. Remarkably, the N-KMO cathode delivers a high reversible capacity of 262 mAh g-1 after 2500 cycles at 1 A g-1 with a capacity retention of 91. Simultaneously, the highest specific capacity can reach 298 mAh g-1 at 0.1 A g-1. Theor. calcns. reveal that the oxygen vacancy and N-doping can improve the elec. cond. of MnO2 and thus account for the outstanding rate performance. Moreover, ex situ characterizations indicate that the energy storage mechanism of the N-KMO cathode is mainly a H+ and Zn2+ co-insertion/extn. process.
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    42. 42
      Wang, J.; Polleux, J.; Lim, J. Pseudocapacitive Contributions to Electrochemical Energy Storage in TiO2 (Anatase) Nanoparticles. J. Phys. Chem. C 2007, 111 (40), 14925– 14931,  DOI: 10.1021/jp074464w
      42
      Pseudocapacitive Contributions to Electrochemical Energy Storage in TiO2 (Anatase) Nanoparticles
      Wang, John; Polleux, Julien; Lim, James; Dunn, Bruce
      Journal of Physical Chemistry C (2007), 111 (40), 14925-14931CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The advantages of using nanostructured materials for electrochem. energy storage have focused on the benefits assocd. with short path lengths. However, another contribution, capacitive effects which become increasingly important at nanoscale dimensions, was studied. Nanocryst. TiO2 (anatase) was studied over a dimensional regime where both capacitive and Li intercalation processes contribute to the total stored charge. An anal. of the voltammetric sweep data was used to distinguish between the amt. of charge stored by these 2 processes. At particle sizes <10 nm, capacitive contributions became increasingly important, leading to greater amts. of total stored charge (gravimetrically normalized) with decreasing TiO2 particle size. The area normalized capacitance is well >100 μF/cm2, confirming that the capacitive contribution was pseudocapacitive. Also, decreasing the particle size to the nanoscale regime led to faster charge/discharge rates because diffusion-controlled Li ion intercalation was replaced by faradaic reactions which occur at the surface of the material. The charge storage and kinetic benefits derived from using nanoscale metal oxides provide an interesting direction for the design of materials that offer both power d. and energy d.
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    43. 43
      Post, J. E.; Appleman, D. E. Chalcophanite, ZnMn3O7·3H2O: new crystal-structure determinations. Am. Mineral. 1988, 73 (11–12), 1401– 1404
      There is no corresponding record for this reference.
    44. 44
      Post, J. E.; Veblen, D. R. Crystal structure determinations of synthetic sodium, magnesium, and potassium birnessite using TEM and the Rietveld method. Am. Mineral. 1990, 75 (5–6), 477– 489
      44
      Crystal structure determinations of synthetic sodium, magnesium, and potassium birnessite using TEM and the Rietveld method
      Post, Jeffrey E.; Veblen, David R.
      American Mineralogist (1990), 75 (5-6), 477-89CODEN: AMMIAY; ISSN:0003-004X.
      The Rietveld method and electron diffraction are used to det., for the first time, the crystal structures of the subcells of synthetic Na-, Mg-, and K-rich birnessite-like phases. The subcells have C2/m symmetry and the unit-cell parameters are a 5.175, 5.049, and 5.149; b 2.850, 2.845, and 2.843; c 7.337, 7.051, and 7.176 Å, and β 103.18°, 96.65°, and 100.76°, for Na-, Mg-, and K-birnessite, resp. The general birnessite structure is analogous to that of chalcophanite. Difference-Fourier analyses combined with Rietveld refinements show that the H2O mols. and interlayer cations occupy different positions in the 3 birnessite structures. Electron diffraction patterns reveal different superstructures that probably arise from ordering of interlayer water mols. and cations for each of the 3 phases.
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    45. 45
      Lafuente, B. The Power of Databases: The RRUFF Project. In Highlights in Mineralogical Crystallography; Armbruster, T.; Danisi, R. M., Eds.; De Gruyter (O), 2016; pp 1– 30.
      There is no corresponding record for this reference.
    46. 46
      Kihara, K.; Donnay, G. Anharmonic thermal vibrations in ZnO. Can. Mineral. 1985, 23 (4), 647– 654
      There is no corresponding record for this reference.
    47. 47
      Borchers, N.; Clark, S.; Horstmann, B. Innovative zinc-based batteries. J. Power Sources 2021, 484, 229309  DOI: 10.1016/j.jpowsour.2020.229309
      47
      Innovative zinc-based batteries
      Borchers, Niklas; Clark, Simon; Horstmann, Birger; Jayasayee, Kaushik; Juel, Mari; Stevens, Philippe
      Journal of Power Sources (2021), 484 (), 229309CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)
      A review. The demand for high-performance, affordable, and safe energy storage solns. is growing, driven in part by the incorporation of fluctuating electricity sources like wind turbines and solar cells in the elec. grid. Batteries offer such a storage soln. in both distributed systems such as households and large-scale industrial systems. The quest for more resource-efficient alternatives to lithium-ion batteries is on its way to meet the increasing demand. Zinc batteries are particularly ecol. friendly due to their use of abundant raw materials and their facile recyclability. High energy densities add to the benefits of this technol. These advantages stem from the use of zinc metal electrodes in combination with effective and affordable aq. electrolytes. Zinc battery types are distinguished by their cathode materials and electrolytic charge carriers. Zinc-air batteries work with oxygen from air and have the potential to offer the highest energy densities. Zinc-flow batteries could enable large scale battery storage. Zinc-ion batteries are a more recent development which promise large power densities and long cycle lives. In this review, these technologies are discussed in detail. We summarize the development status of each technol., criticize typical deficiencies of current studies, discuss technol. challenges, and highlight promising future research directions.
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    48. 48
      Wu, D.; King, S. T.; Sadique, N. Operando investigation of aqueous zinc manganese oxide batteries: multi-stage reaction mechanism revealed. J. Mater. Chem. A 2023, 11 (30), 16279– 16292,  DOI: 10.1039/D3TA01549A
      There is no corresponding record for this reference.
    49. 49
      Zhang, N.; Ji, Y. R.; Wang, J. C. Understanding of the charge storage mechanism of MnO2-based aqueous zinc-ion batteries: Reaction processes and regulation strategies. J. Energy Chem. 2023, 82, 423– 463,  DOI: 10.1016/j.jechem.2023.03.052
      49
      Understanding of the charge storage mechanism of MnO2-based aqueous zinc-ion batteries: Reaction processes and regulation strategies
      Zhang, Nan; Ji, Yu-Rui; Wang, Jian-Cang; Wang, Peng-Fei; Zhu, Yan-Rong; Yi, Ting-Feng
      Journal of Energy Chemistry (2023), 82 (), 423-463CODEN: JECOFG; ISSN:2095-4956. (Science Press)
      A review. Though secondary aq. Zn ion batteries (AZIBs) have been received broad concern in recent years, the development of suitable cathode materials of AZIBs is still a big challenge. The MnO2 has been deemed as one of most hopeful cathode materials of AZIBs on account of some extraordinary merits, such as richly natural resources, low toxicity, high discharge potential, and large theor. capacity. However, the crystal structure diversity of MnO2 results in an obvious various of charge storage mechanisms, which can cause great differences in electrochem. performance. Furthermore, several challenges, including intrinsic poor cond., dissoln. of manganese and sluggish ion transport dynamics should be conquered before real practice. This work focuses on the reaction mechanisms and recent progress of MnO2-based materials of AZIBs. In this review, a detailed review of the reaction mechanisms and optimal ways for enhancing electrochem. performance for MnO2-based materials is proposed. At last, a no. of viewpoints on challenges, future development direction, and foreground of MnO2-based materials of aq. zinc ions batteries are put forward. This review clarifies reaction mechanism of MnO2-based materials of AZIBs, and offers a new perspective for the future invention in MnO2-based cathode materials, thus accelerate the extensive development and commercialization practice of aq. zinc ions batteries.
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    50. 50
      Wang, M.; Feng, Z. Pitfalls in X-ray absorption spectroscopy analysis and interpretation: A practical guide for general users. Curr. Opin. Electrochem. 2021, 30, 100803  DOI: 10.1016/j.coelec.2021.100803
      50
      Pitfalls in X-ray absorption spectroscopy analysis and interpretation: A practical guide for general users
      Wang, Maoyu; Feng, Zhenxing
      Current Opinion in Electrochemistry (2021), 30 (), 100803CODEN: COEUCY; ISSN:2451-9111. (Elsevier B.V.)
      A review. Despite the growing popularity of X-ray absorption spectroscopy (XAS) in scientific research, many researchers do not receive formalized training on this technique. Some of them learned from online resources, which only briefly introduce XAS and its applications. Here, this article aims to provide the overview of tips about the XAS anal., general rules, as well as required information for presenting XAS data in publications, and some common mistakes in XAS data interpretations. Armed with these basics, the motivated aspiring XAS researchers will find existing resources more accessible and can progress much faster in understanding and using XAS.
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    51. 51
      Wang, J.; Liu, X.; Hou, Z. Enhanced sodium ion storage in MnO2 through asymmetric orbital hybridization induced by spin-paired ion doping. J. Mater. Chem. A 2024, 12 (5), 3151– 3158,  DOI: 10.1039/D3TA06776A
      There is no corresponding record for this reference.
    52. 52
      Jiang, Y.; Yuan, L.; Wang, X. Jahn–Teller Disproportionation Induced Exfoliation of Unit-Cell Scale ϵ-MnO2. Angew. Chem., Int. Ed. 2020, 59 (50), 22659– 22666,  DOI: 10.1002/anie.202010246
      52
      Jahn-Teller Disproportionation Induced Exfoliation of Unit-Cell Scale ε-MnO2
      Jiang, Yilan; Yuan, Long; Wang, Xiyang; Zhang, Wei; Liu, Jinghai; Wu, Xiaofeng; Huang, Keke; Li, Yefei; Liu, Zhipan; Feng, Shouhua
      Angewandte Chemie, International Edition (2020), 59 (50), 22659-22666CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Exfoliation of non-layered (structurally) bulk materials at the nanoscale is challenging because of the strong chem. bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top-down method to exfoliate ε-MnO2 nanosheets in a family of charge-ordered La1-xAExMnO3 (AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn-Teller disproportionation effect of Mn3+ and bond-strength differences. ε-MnO2 crystd. into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidn. activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton-induced Mn3+ disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two-dimensional nanosheet materials with non-layered structures.
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    53. 53
      Wang, P.-F.; Jin, T.; Zhang, J. Elucidation of the Jahn-Teller effect in a pair of sodium isomer. Nano Energy 2020, 77, 105167  DOI: 10.1016/j.nanoen.2020.105167
      53
      Elucidation of the Jahn-Teller effect in a pair of sodium isomer
      Wang, Peng-Fei; Jin, Ting; Zhang, Jiaxun; Wang, Qin-Chao; Ji, Xiao; Cui, Chunyu; Piao, Nan; Liu, Sufu; Xu, Jijian; Yang, Xiao-Qing; Wang, Chunsheng
      Nano Energy (2020), 77 (), 105167CODEN: NEANCA; ISSN:2211-2855. (Elsevier Ltd.)
      Jahn-Teller distorted Mn(III) (t32ge1g) ions play a key role in the performance of manganese-based layered oxides. Here we show that there is an obvious relationship between the Jahn-Teller distortion of a trivalent manganese and the electrochem. in a pair of Na isomer, namely orthorhombic and hexagonal P2-type Na2/3Mn0.9Ti0.1O2 having the same compn. It is found that more reversible phase transformations, higher working voltage and faster Na diffusion correlated with Jahn-Teller effect are found for distorted P'2-Na2/3Mn0.9Ti0.1O2 upon Na+ ions extn./insertion. Such Jahn-Teller distorted Mn assisted Na migration enables that the orthorhombic Na2/3Mn0.9Ti0.1O2 delivers a high specific capacity of 204.0 mA h g-1 with a 2.7 V av. working voltage, reaching 550 Wh Kg-1 with both better cycle stability (a capacity retention of 82.3% after 100 cycles) and enhanced rate capability (97.8 mA h g-1 cycled at 10C) in Na cell in contrast with undistorted Na2/3Mn0.9Ti0.1O2. This strategy for understanding the Jahn-Teller effect of P2-type compds. at orbital energy level grasps new insight into designing high energy d. pos. electrode materials for Na-ion batteries.
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    54. 54
      Zhao, Y.; Zhang, S.; Zhang, Y. Vacancy-rich Al-doped MnO2 cathodes break the trade-off between kinetics and stability for high-performance aqueous Zn-ion batteries. Energy Environ. Sci. 2024, 17 (3), 1279– 1290,  DOI: 10.1039/D3EE01659E
      There is no corresponding record for this reference.
    55. 55
      Heo, J.; Chong, S.; Kim, S. Suppressing Charge Disproportionation of MnO2 Cathodes in Rechargeable Zinc Ion Batteries via Cooperative Jahn-Teller Distortion. Batteries Supercaps 2021, 4 (12), 1881– 1888,  DOI: 10.1002/batt.202100181
      There is no corresponding record for this reference.
    56. 56
      Zhang, L.; Miao, L.; Zhang, B. A durable VO2(M)/Zn battery with ultrahigh rate capability enabled by pseudocapacitive proton insertion. J. Mater. Chem. A 2020, 8 (4), 1731– 1740,  DOI: 10.1039/C9TA11031C
      56
      A durable VO2(M)/Zn battery with ultrahigh rate capability enabled by pseudocapacitive proton insertion
      Zhang, Lishang; Miao, Ling; Zhang, Bao; Wang, Jinsong; Liu, Jia; Tan, Qiuyang; Wan, Houzhao; Jiang, Jianjun
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2020), 8 (4), 1731-1740CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Energy storage devices with low-cost and high-safety features are essential because of the continued consumption of fossil fuels. Aq. zinc ion batteries, owing to their superior safety, high abundance and high theoretic capacity, have attracted increasing attention. Herein, for the first time, the M phase VO2 integrated with carbon nanotubes as a binder-free cathode for zinc ion batteries was studied. The as-prepd. binder-free cathode shows ultrahigh rate performance with 248 mA h g-1 at 2 A g-1, 232.6 mA h g-1 (93.8% maintained compared to 2 A g-1) at 20 A g-1 and 194.9 mA h g-1 at 40 A g-1. Good stability was achieved with 84.5% retention after up to 5000 cycles at 20 A g-1. This ultrahigh capacity retention at such high current densities is comparable among the reported studies. To fundamentally reveal the electrochem. mechanism, the bond valence method was employed to unravel the migration pathway of H+/Zn2+ in VO2(M). The H+ diffusion pathway was fluent, while the Zn2+ route had a narrow and blocked passage, which was consistent with the reversible deposition/dissoln. of hydroxyzinc sulfate hydrate in the electrochem. process. The pseudocapacitive proton insertion mechanism can be a promising strategy to explore cathode materials for aq. zinc ion batteries.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.4c07239.

    • The electrochemical cell for the in situ XAS measurement, XPS of the NH4-MnO2 powder, Rietveld refinement results of the XRD spectra, EPR, GCD, CV, and Dunn’s analysis, diffusivity, EIS, XPS of the K-MnO2 cathode, Mn K-edge EXAFS, FE-SEM of the discharged cathodes, operando XRD of K-MnO2, Raman spectra, DFT-optimized models and description of DFT calculations, and Zn K-edge EXAFS (PDF)


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