ACS Publications. Most Trusted. Most Cited. Most Read
A Practical and Sustainable Ni/Co-Free High-Energy Electrode Material: Nanostructured LiMnO2
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Cent. Sci. 2024, 10, 9, 1718-1732
  • Open Access
Article

A Practical and Sustainable Ni/Co-Free High-Energy Electrode Material: Nanostructured LiMnO2
Click to copy article linkArticle link copied!

  • Yuka Miyaoka
    Yuka Miyaoka
    Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    More by Yuka Miyaoka
  • Takahito Sato
    Takahito Sato
    Department of Applied Chemistry, Tokyo Denki University, 5 Senju Asahi-Cho, Adachi, Tokyo 120-8551, Japan
    More by Takahito Sato
  • Yuna Oguro
    Yuna Oguro
    Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    More by Yuna Oguro
  • Sayaka Kondo
    Sayaka Kondo
    Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
    More by Sayaka Kondo
  • Koki Nakano
    Koki Nakano
    Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
    More by Koki Nakano
  • Masanobu Nakayama
    Masanobu Nakayama
    Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
    More by Masanobu Nakayama
    Orcidhttps://orcid.org/0000-0002-5113-053X
  • Yosuke Ugata
    Yosuke Ugata
    Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    Advanced Chemical Energy Research Center, Institute of Advanced Sciences, Yokohama National University, Yokohama 240-0067, Japan
    More by Yosuke Ugata
    Orcidhttps://orcid.org/0000-0002-8233-6725
  • Damian Goonetilleke
    Damian Goonetilleke
    School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
    More by Damian Goonetilleke
    Orcidhttps://orcid.org/0000-0003-1033-4787
  • Neeraj Sharma
    Neeraj Sharma
    School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
    More by Neeraj Sharma
    Orcidhttps://orcid.org/0000-0003-1197-6343
  • Alexey M. Glushenkov
    Alexey M. Glushenkov
    Research School of Chemistry, The Australian National University, Canberra, ACT 2600, Australia
    More by Alexey M. Glushenkov
    Orcidhttps://orcid.org/0000-0002-4851-839X
  • Satoshi Hiroi
    Satoshi Hiroi
    Faculty of Materials for Energy, Shimane University, Matsue, Shimane 690-8504, Japan
    More by Satoshi Hiroi
    Orcidhttps://orcid.org/0000-0001-5058-6757
  • Koji Ohara
    Koji Ohara
    Faculty of Materials for Energy, Shimane University, Matsue, Shimane 690-8504, Japan
    More by Koji Ohara
  • Koji Takada
    Koji Takada
    Tosoh Corporation, 4560 Kaisei-cho, Shunan-Shi, Yamaguchi 746-8501, Japan
    More by Koji Takada
  • Yasuhiro Fujii
    Yasuhiro Fujii
    Tosoh Corporation, 4560 Kaisei-cho, Shunan-Shi, Yamaguchi 746-8501, Japan
    More by Yasuhiro Fujii
  • Naoaki Yabuuchi*
    Naoaki Yabuuchi
    Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    Advanced Chemical Energy Research Center, Institute of Advanced Sciences, Yokohama National University, Yokohama 240-0067, Japan
    *E-mail: [email protected]
    More by Naoaki Yabuuchi
    Orcidhttps://orcid.org/0000-0002-9404-5693
Open PDFSupporting Information (1)

ACS Central Science

Cite this: ACS Cent. Sci. 2024, 10, 9, 1718–1732
Click to copy citationCitation copied!
https://doi.org/10.1021/acscentsci.4c00578
Published August 26, 2024

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Ni/Co-free high-energy positive electrode materials are of great importance to ensure the sustainability of Li-ion battery production and its supply chain in addition to minimizing environmental impact. Here, nanostructured LiMnO2 with both orthorhombic/monoclinic layered domains is synthesized, and its lithium storage properties and mechanism are examined. High-energy mechanical milling is used to convert the metastable and nanosized LiMnO2 adopting the cation-disordered rocksalt structure to an optimal domain-segregated layered LiMnO2. This positive electrode produces an energy density of 820 W h kg–1, achieved by harnessing a large reversible capacity with relatively small voltage hysteresis on electrochemical cycles. Moreover, voltage decay for cycling, as observed for Li-excess Mn-based electrode materials, is effectively mitigated. Furthermore, by determining the structure–property relationships of different LiMnO2 polymorphs, LiMnO2 with similar domain structure and surface area is successfully synthesized with an alternative and simpler method, without the metastable precursor and high-energy mechanical milling. The cyclability of domain-containing LiMnO2 is also improved with the use of a highly concentrated electrolyte coupled with a lithium phosphate coating due to the suppression of Mn dissolution. These findings maximize the possibility of the development of high-energy, low-cost, and practical rechargeable batteries made from sustainable and abundant Mn sources without Ni/Co.

This publication is licensed under

CC-BY 4.0 .
  • cc licence
  • by licence
Copyright © 2024 The Authors. Published by American Chemical Society

Subjects

what are subjects

Synopsis

Domain-structured LiMnO2 with large surface area has been synthesized and proposed as Co/Ni-free positive electrode materials with high-energy density for practical Li-ion battery applications.

Introduction

Click to copy section linkSection link copied!
The electrification of worldwide mobility solutions is effectively a prerequisite to minimize dependence on fossil fuels as energy resources. Among rechargeable energy storage devices, Li-ion batteries provide the highest gravimetric and volumetric energy density, and the technology has been optimized and heavily researched in the past three decades since its first commercialization in 1991. Now, Li-ion batteries are able to provide power for electric vehicles, which has in part been enabled by the significant decline in their cost and continual improvements in energy density. (1) Although the global market of electric vehicles is rapidly growing, further reduction of battery cost is necessary to allow for further penetration of electric vehicles into the automobile market. The price of reagents and materials becomes critical as the cost of batteries decreases, (2) and the positive electrode is the most expensive component in Li-ion batteries. (3) Spinel-type LiMn2O4 and olivine-type LiFePO4 have been studied and practically used as cost-effective positive electrode materials, but the energy density of these low-cost materials is limited to approximately 500 W h kg–1 based on Li/Li+ which is significantly lower than that of Ni-based layered materials (∼750 W h kg–1). Consequently, Ni-based layered materials with cationic redox reaction of Ni ions, i.e., Ni2+/Ni3+/Ni4+, are mainly used in Li-ion batteries for state-of-the-art electric vehicles, which result in extended cruising distances. Ni-based layered materials, derivatives of LiNiO2, e.g., LiNi1–x–yMnxCoyO2, (4−8) are often plagued by the relatively high cost of Co and Ni compounds due to their limited abundance in the crust and the mining/processing steps involved to make battery grade electrodes. Moreover, the cost of Ni is increasing as the electric vehicle market expands, and a high price risk or volatility is anticipated in the future, not to mention supply chain challenges. (9) Therefore, the development of Ni-/Co-free high-energy positive electrode materials is desired to further reduce the cost of Li-ion batteries and to ensure its sustainability.
Recently, Li2MnO3-based electrode materials with a layered structure and its derivatives have been extensively studied as potential high-energy and low-cost positive electrode materials. Higher energy density, ∼900 W h kg–1, can be realized using Li2MnO3-based electrode materials with anionic redox reaction, whereby the Li extracted from host structures is compensated for by negatively charged oxygen species. Nevertheless, reversibility of anionic redox is insufficient, and gradual oxygen loss upon cycling results in the lowering of operating voltage. (10,11) Large voltage hysteresis on charge–discharge for anionic redox is another practical issue. In addition, Mn-based Li-excess oxides with a rocksalt structure have also been reported, and an even higher energy density of 1000–1100 W h kg–1 has been demonstrated. (12,13) However, similar problems to the layered structure are noted for these rocksalts, cyclability, and voltage hysteresis. Such disadvantages of these electrode materials currently hinder their use in practical applications, and therefore, further stabilization of anionic redox and the mitigation of voltage loss are necessary.
Among the Mn-based electrode materials, as a counterpart of LiCoO2 and LiNiO2, stoichiometric LiMnO2 was also extensively studied as a positive electrode material. (14−18) Thermodynamically stable LiMnO2 crystallizes in a so-called “zigzag”-type layered structure with orthorhombic space-group symmetry. (14) During electrochemical cycling, a particularly unusual phase transition is noted where a spinel-like phase with low crystallinity is eventually formed. (17) Unlike the more conventional phase transitions noted in intercalation compounds, where on either charge or discharge, Li extraction or insertion in the case of the positive electrode, a phase transition is noted, e.g., from hexagonal LiCoO2 to monoclinic Li∼0.5CoO2, the transition in LiMnO2 to the spinel-like phase is significantly more gradual and occurs with cycling coupled with Mn migration, over a number of charge/discharge cycles. This implies a kinetic inhibition to this phase transition.
In LiMnO2 reversible capacities increase to ∼220 mA h g–1 at 8.3 mA g–1, after the formation of the spinel-like phase. (19) Nevertheless, the phase transition kinetics are quite slow, and over 30 cycles are required to obtain such a large reversible capacity, which is likely associated with the formation of the spinel-like phase and its reversible cycling. Moreover, energy efficiency is low, and approximately 20% of the energy density is lost, presumably associated with the inferior electrode kinetics. Therefore, there is a coupled relation between the generation of the spinel-like phase and optimal electrochemical performance.
Another polymorph of LiMnO2 adopting monoclinic space group symmetry with a layered structure but metastable was prepared by a soft chemistry route from NaMnO2 and delivered ca. 180 mA h g–1 even after 100 cycles. (20) However, initial Coulombic efficiency is limited to only 70% and a long activation process (coupled with the increase in reversible capacity) over 40 cycles is required to attain high reversible capacities. The phase stability and reversibility of LiMnO2 appear to be correlated and synthesizing the appropriate phase or composite with high reversibility may be the answer to an excellent electrode material.
In this article, nanostructured LiMnO2, which contains both orthorhombic and monoclinic layered domains, is synthesized, and its lithium storage properties are systematically examined. First, metastable and nanosized LiMnO2 with a rocksalt structure is prepared by mechanical milling, (21) and this sample is used as a precursor. Heat-treatment of rocksalt LiMnO2, which is energetically unstable compared with orthorhombic and monoclinic layered phases, results in the crystallization of LiMnO2 with the unique nanostructure. These nanostructures influence phase transition processes, resulting in a spinel-like phase with electrochemical cycling. The grain size remains comparable to that of metastable rocksalt LiMnO2 (∼150 nm) prepared by mechanical milling, which is found to be essential in producing a high-performance electrode material without Ni/Co. Moreover, these findings and understanding for different LiMnO2 polymorphs permit the direct synthesis of LiMnO2 with a similar nanostructure without the use of the metastable precursor and high-energy ball milling. From these results, the possibility of developing practical Ni/Co-free high-energy positive electrode materials is both discussed and demonstrated.

Results and Discussion

Click to copy section linkSection link copied!

Synthesis of Nanostructured LiMnO2 and Structural Characterization

The precursor metastable and nanosized LiMnO2 with a cubic rocksalt structure was prepared by mechanical milling of a zigzag layered LiMnO2 with orthorhombic symmetry, as described in the Experimental Methods, using a process which has been previously detailed in the literature. (21) Synchrotron X-ray diffraction (XRD) patterns of a thermodynamically stable phase, orthorhombic LiMnO2, and metastable phase, cubic rocksalt LiMnO2, are compared in Figure 1a. The reflections for the orthorhombic phase are completely lost after mechanical milling, and broad reflections, which can be assigned to the cubic phase, are observed. Crystalline sizes of cubic LiMnO2 range from 3 to 5 nm based on Scherrer analysis. (21) In addition, the particle morphology from orthorhombic to rocksalt LiMnO2 is completely changed as observed by field emission scanning electron microscopy (FE-SEM) in Figure 1b and Supporting Figure S1a. Large particle sizes, ∼10 μm, for orthorhombic LiMnO2 are effectively reduced to submicron scale, which consists of smaller grains, 50–150 nm (Figure 1b).

Figure 1

Figure 1. Synthesis of four different LiMnO2 polymorphs: (a) XRD patterns and schematic illustrations of crystal structures, (b) SEM images, (c) STEM images of heat-treated LiMnO2, (d) schematic illustration of domain structures for heat-treated LiMnO2, and (e) pair distribution functions of orthorhombic, heat-treated and monoclinic LiMnO2. Schematic illustrations of crystal structures were drawn using the VESTA program. (61)

High Resolution Image
Download MS PowerPoint Slide
Heat-treatment of metastable cubic rocksalt LiMnO2 at 700 °C results in the formation of LiMnO2 with a different crystal structure. Note, all reflections after heat-treatment can be assigned to the orthorhombic phase, as shown in Figure 1a, but intensity and area (peak shapes) of reflections are clearly different for as prepared orthorhombic LiMnO2 and ball-milled and heat-treated LiMnO2. For instance, the reflection intensity of (110) at 2θ ∼ 8° is lower whereas peak intensity of (021) at 2θ ∼ 14.3° is higher in the ball-milled and heat-treated LiMnO2 relative to as-prepared LiMnO2 (Supporting Figure S1b). This observation is likely to originate from structural (dis)ordering in the orthorhombic phase. Similar intensity fluctuations are noted for LiMnO2 synthesized by the hydrothermal method (22) and the samples synthesized with lithium deficiency. (23)
For comparison, another metastable polymorph of LiMnO2 was prepared by ion-exchange from NaMnO2 with the in-plane distorted α-NaFeO2-type layered structure, (15) and its synchrotron XRD diffraction pattern is also shown in Figure 1a. Mn3+ is a typical Jahn–Teller ion, so in-plane distortion for transition metal layers is induced, leading to a monoclinic lattice. At 2θ ∼ 6° the most intense reflection, (001) is clearly observed for monoclinic layered LiMnO2 and it is important to note that the small reflection at the same 2θ position is also observed in ball-milled and heat-treated LiMnO2. Both monoclinic and orthorhombic phases consist of common oxygen packing, a cubic-close-packed structure (Supporting Figure S1c), and only arrangements of cations are different at the octahedral sites. To examine the origin of the structural (dis)order, the formation energy of LiMnO2 with three different polymorphs, orthorhombic zigzag layered, monoclinic layered, and cubic rocksalt structures, is computed by density functional theory (DFT) calculations, and the results are summarized in Supporting Figure S2. The energy of cubic rocksalt LiMnO2 is unstable by 50 and 64 meV per atom when compared with the monoclinic and orthorhombic phases, respectively. XRD data show evidence of the nucleation of the orthorhombic phase on heating of rocksalt LiMnO2. However, a growth rate of the orthorhombic phase along the b/c-axis directions would be faster than or different to that of a-axis direction, leading to the formation of planar defects. This would be associated with the mismatch of the Li and Mn sites and thus would not form the ideal zigzag layered structure on growth in different directions or domains. This mismatch locally results in the formation of domains of the α-NaFeO2-type monoclinic layered structure as shown in Figure 1d. In addition, the energy difference between monoclinic layered and orthorhombic phases is relatively small; therefore, the possibility of nucleation and growth of the monoclinic phase cannot be eliminated, especially if it is seeded at the planar defect sites described above. Indeed, the small (001) at 2θ ∼ 6°, which is not observed for the pure orthorhombic phase, is detected for the ball-milled and heat-treated LiMnO2. The presence of planar defects is directly visualized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) as shown in Figure 1c and Supporting Figure S3. Different structural domains are clearly visualized in the STEM images, and the domain size for the orthorhombic phase is relatively large, as shown in Supporting Figure S3. The presence of Li and O is also partly observed in annular bright-field (ABF) STEM images. Similar structural (dis)ordering is also observed for NaMnO2, and such planar defects are also regarded as the presence of multiple twinning in particles. (24)
To further validate the planar defects in the heat-treated sample, XRD patterns with different layered domains were simulated using the DIFFaX program, (25) and similar analysis was also conducted for the previously reported Li-deficient phase. (15) The fraction of monoclinic layered domains was continuously altered from 0 to 100% versus orthorhombic layered domains, and XRD patterns were simulated for these conditions (Supporting Figure S4). The observed XRD pattern, including (110) with the broad profile, is successfully reproduced when 30% of the monoclinic layered domains coexists with the orthorhombic structure. This finding is further supported by total X-ray total scattering study where high-energy X-ray scatting data at E = 61.4 keV were collected and the corresponding experimental X-ray pair distribution function is shown in Supporting Figure S5. The pair distribution function of the ball-milled and heat-treated LiMnO2 is reminiscent of both orthorhombic and monoclinic phases and can be considered an average profile or between these two structures, as compared in Figure 1e. All structural analysis conducted in this study concludes that ball-milled and heat-treated LiMnO2 has both the orthorhombic zigzag layered and α-NaFeO2-type monoclinic layered domains. Note that grain sizes of the sample after heat treatment at 700 °C remain comparable to cubic rocksalt LiMnO2, approximately 100–150 nm (Figure 1b), and smoothly faceted grains are found after heat-treatment without significant reduction of surface area.

Electrode Properties of Nanostructured LiMnO2

Lithium storage properties of LiMnO2 obtained by ball-milling and heat treatment of metastable cubic rocksalt LiMnO2 were examined. Results are also compared with different LiMnO2 polymorphs and pure orthorhombic and monoclinic layered structures. The particle size of as-prepared orthorhombic LiMnO2 is large and this adversely impacts performance, therefore this sample was mixed with acetylene black (10 wt % in a mass ratio) and ball milled to reduce the particle size (Supporting Figure S1). The particle size of the sample is effectively reduced by ball milling, and electrode performance is also significantly improved as shown in Supporting Figure S6a. Note this sample remains orthorhombic, as the ball milling conditions were optimized to minimize or avoid the formation of the cubic rocksalt LiMnO2. Similarly, a carbon composited electrode was also prepared from monoclinic layered LiMnO2, and the electrode performance of the as-prepared sample is shown in Supporting Figure S6b. Charge/discharge curves of these three different LiMnO2 polymorphs are shown for the initial 6 cycles and for 6–10th cycles in Figure 2a and 2b, respectively. The data of orthorhombic and monoclinic LiMnO2 were obtained from the carbon-composite samples while the as-prepared sample was used for ball-milled and heat-treated LiMnO2, without ball milling with acetylene black. The initial charge capacity reaches 245 mA h g–1 for the ball-milled and heat-treated sample, which is clearly larger than the as-prepared orthorhombic sample. (19,26) Moreover, the initial discharge capacity reaches 235 mA h g–1 for the ball-milled and heat-treated sample. Reversible capacities increase in the initial several cycles for both samples, characteristic for LiMnO2 and are typically associated with a phase transition into a spinel-like phase. The largest reversible capacity is observed at third and eighth cycles for the heat-treated and carbon composited orthorhombic samples respectively on electrochemical cycling at a rate of 10 mA g–1. In contrast, the largest reversible capacity of 245 mA h g–1 for monoclinic layered LiMnO2 is observed at the initial cycle, and no further increase in reversible capacity is evidenced for continuous cycles. No increase in reversible capacity is observed on 6–10th cycles for the heat-treated and monoclinic samples (Figure 1b), suggesting that phase transition kinetics to the spinel-like phase on electrochemical cycling are faster when compared with those of orthorhombic LiMnO2. Charge/discharge curves for these samples during 30 cycles at 10 mA g–1 is shown in Supporting Figure S7, and the dQ/dE differential capacity plots are compared in Figure 2c. All samples show large reversible capacities, 240–260 mA h g–1, with similar capacity retention with continuous cycling until cycle 30. Nevertheless, voltage profiles and thus energy density are completely different for the three samples. The presence of a voltage plateau at 2 V especially for the discharge process is noted for the as-prepared orthorhombic and monoclinic samples. This trend is further visualized in differential capacity plots in Figure 2c. Smaller polarization with a highly reversible 3 V redox reaction is clearly evidenced for the ball-milled and heat-treated sample, and interestingly, polarization is gradually reduced upon electrochemical cycling (Figure 2c). Average voltage changes for the heat-treated and orthorhombic samples are also plotted in Figure 2d. Although discharge capacity is gradually lost on continuous cycling (220 mA h g–1 at 30th cycle at a rate of 10 mA g–1, Figure 2e for both samples), no decrease in average voltage is noted in Figure 2d. The decrease in average discharge voltage is a critical problem for the Li-rich system, e.g., Li1.2Co0.13Ni0.13Mn0.54O2 (see Supporting Figure S8), which hinders its use for practical applications. The problem of voltage decay on electrochemical cycling is effectively mitigated for LiMnO2 because the large reversible capacity is expected to originate solely from Mn cationic redox without unstable O anionic redox.

Figure 2

Figure 2. Electrochemistry of different LiMnO2 polymorphs: Galvanostatic charge/discharge curves where (a) shows 1st–5th cycles and (b) 6th–10th cycles, (c) differential capacity plots, (d) changes in average discharge voltage, (e) capacity retention, (f) quasi-open circuit voltage for the 10th cycle, (g) energy density variations, and (h) discharge/charge rate capability of heat-treated LiMnO2.

High Resolution Image
Download MS PowerPoint Slide

Comparison of Voltage Hysteresis and Energy Density of LiMnO2 Polymorphs

As shown in Figure 2c, differential capacity plots reveal that LiMnO2 polymorphs show different voltage hysteresis, which influences their energy density as electrode materials. Quasi open-circuit voltages (QOCVs) for different polymorphs are compared in Figure 2f. The cells were charged/discharged for 1 h at a rate of 10 mA g–1, and then were rested at open-circuit for 4 h. The largest voltage hysteresis is observed for monoclinic layered LiMnO2. Note that the largest voltage hysteresis for monoclinic LiMnO2 is observed for the 2–3 V region, which is almost nonexistent for heat-treated LiMnO2 after 4 h relaxation. Additional hysteresis is observed in the 3–4 V region for all samples, but the smallest hysteresis is evidenced for heat-treated LiMnO2. QOCVs in Figure 2f were collected at the 10th cycle. QOCVs of heat-treated LiMnO2 at the fifth cycle is also shown in Supporting Figure S9, and smaller hysteresis is found at 10th cycle. Although three different LiMnO2 polymorphs show distinct charge/discharge profiles in Figure 2b, the variations are explained as the difference in electrode kinetics, especially for the 2–3 V region as clearly found in Figure 2f. Such voltage hysteresis observed under nearly equilibrium conditions is also known for spinel Li1+xMn2O4 and changes as a function of particle size. For spinel Li1+xMn2O4 this was suggested to originate from the difference in kinetics of lithiation/delithiation coupled with the distortion of crystal lattice. (27) Similar phenomena are expected for LiMnO2 polymorphs but associated with the spinel-like phase formation with electrochemical cycling and potentially their lithiation/delithiation kinetics. These differences in voltage hysteresis and electrode kinetics result in the highest energy density for heat-treated LiMnO2 (Figure 2g) compared to the other polymorphs. The largest energy density is estimated to be 820 W h kg–1 for heat-treated LiMnO2, which is larger than those of the Ni-rich layered materials (Supporting Figure S10). (28) Moreover, voltage decay on the electrochemical cycle was not observed for LiMnO2. Rate capability of heat-treated LiMnO2 is also shown in Figure 2h. Nearly 50% of capacity is lost at a discharge rate of 200 mA g–1, corresponding to approximately 0.7 C. The electrode kinetics on discharge are not superior to Ni-rich electrode materials as expected from inferior kinetics on discharge (Figure 2f). Nevertheless, from the voltage relaxation processes, superior kinetics on “charge” are anticipated because of small voltage hysteresis compared with discharge. Indeed, much better rate-capability on charge is obtained, as shown in Figure 2h. Quick charge ability is an important characteristic for upcoming battery applications, especially for electric vehicles, and it is concluded that LiMnO2 is a suitable electrode material for this purpose. It is noted that such inferior electrode kinetics on discharge associated with the lattice distortion is expected to lead to the capacity loss at the 3 V region on continuous cycles (Supporting Figure S8e). In contrast, the superior reversibility at the 4 V region results in better capacity retention, leading to gradual increase for average discharge voltage (Figure 2d and Supporting Figure S8h). Voltage decay observed for Li-rich Mn-based oxides is, therefore, not observed for LiMnO2.

Reaction Mechanisms of Nanostructured LiMnO2

As determined above, electrochemical properties, especially aspects such as voltage hysteresis and electrode kinetics, are highly dependent on the cation arrangements and migration pathways in LiMnO2 with different crystal structures. Reaction mechanisms of these samples were examined using synchrotron XRD, and the structural evolution with electrochemical cycling is compared in Supporting Figure S11. For the orthorhombic LiMnO2 there is a clear structural transformation at the first discharge which is essentially complete by the fifth discharge and a new low crystallinity or nanosized phase is formed (Supporting Figure S11a). In contrast, minimal changes and a maintenance of crystallinity is shown for monoclinic LiMnO2 at the first and fifth discharge states (Supporting Figure S11c). However, it is also noted that certain reflections are sharper, e.g., at 2θ ∼ 19°, which may indicate the presence of a tetragonal phase such as Li2Mn2O4, a lithiated phase of cubic spinel LiMn2O4. (29) The cubic symmetry for the spinel phase is lost by the enrichment of Jahn–Teller active ions (high-spin Mn3+), and the structural distortion caused by Jahn–Teller ions results in the stabilization of the tetragonal phase. (30) Synchrotron XRD patterns of LiMnO2 samples after 5 cycles are compared in Figure 3a. Crystallinity of the samples is clearly different, and monoclinic LiMnO2 after 5 cycles shows the highest crystallinity. The lowest crystallinity is noted for orthorhombic LiMnO2 after 5 cycles, and peak positions are different compared with those of the sample derived from monoclinic LiMnO2. This phase (lowest crystallinity) cannot be assigned to tetragonal Li2Mn2O4, and this sample is regarded as a low crystallinity cubic spinel phase without tetragonal distortion (see Supporting Figure S12). This phase is also classified as a partial cation-ordered rocksalt oxide with cubic symmetry and will be discussed in a later section. Heat-treated LiMnO2 with monoclinic layered domains also changes into a lower crystallinity phase, but its crystallinity is clearly higher than that of the orthorhombic phase after 5 cycles. Moreover, the reflections are mainly assigned to the tetragonal spinel, probably with a partial presence of a cubic spinel phase.

Figure 3

Figure 3. Structural characterization of different LiMnO2 polymorphs: (a) XRD patterns after 5 cycles. (b) Contour plot of operando XRD patterns, (c) X-ray absorption spectra, and (d) a high-resolution STEM image of heat-treated LiMnO2. The data of (d) was taken after 5 cycles. For (b), the 1st charge has a slight voltage drop around 150 min and to compensate and reach 4.8 V around 220 min the cell underwent the profile shown.

High Resolution Image
Download MS PowerPoint Slide
Details of the phase transition for heat-treated LiMnO2 were further analyzed by an operando synchrotron XRD study (Figure 3b and Supporting Figure S13a and b). The ball-milled and heat-treated LiMnO2 electrode shows featured previously mentioned, unobservable (110) and higher intensity (021) reflections relative to the structural model of orthorhombic LiMnO2. Furthermore, the monoclinic phase was clearly observable as previously mentioned; see the (001) reflection in Supporting Figure S13c. The reflection at 2θ ∼ 7.3° is observed before charge corresponding to the orthorhombic (010) reflection shows a dramatic reduction in intensity with charge to 4.8 V but the reflection is still visible (see Supporting Figure S13c). In this process, this reflection splits into two, original orthorhombic and a secondary phase, and a change in the 2θ values are noted. This secondary phase is most likely an orthorhombic phase with a slightly expanded lattice by Li extraction, considering the smaller 2θ value. During discharge to 1.5 V, no change in the intensity or 2θ value for the orthorhombic (010) reflection is noted, but subtle changes in the 2θ value for the reflection associated with the secondary phase are noted. The presence of the orthorhombic reflection after the initial cycle is consistent with ex-situ XRD data (Supporting Figure S11). However, the orthorhombic phase almost disappears on the second charge process, indicating that the phase transition to the spinel-like phase is relatively fast for the heat-treated sample. The secondary phase remains relatively stable once formed and appears to slowly lose reflection intensity on the charging or 4.8 V potentiostatic hold steps. Similarly, the monoclinic phase shows a reduction in intensity during first charge and then remains relatively stable until the third charge and potentiostatic hold process, where the reflection noticeably broadens (Supporting Figure S13c). Furthermore, the operando XRD study reveals that the phase transition process for essentially all of the LiMnO2 phases predominantly occurs on charge, and this is clearly emphasized when the potential at 4.8 V is held (Supporting Figure S13c).
The formation of the spinel-like phase from the starting mixture of the orthorhombic and monoclinic in ball-milled and heat-treated LiMnO2 is rapid and occurs on the first charge process as shown in Supporting Figure S13d and e. By the end of first charge, the spinel-like reflections, cf. (200) as shown in Supporting Figure S13d, are clearly visible and very intense in the XRD patterns. These reflections are very broad indicating nanosized particles, estimated via the Scherrer equation on the spinel (220) reflection to be 86 nm on first charge and reducing marginally to 58 nm on third charge. Once formed, the spinel phase shows minimal changes with electrochemical cycling; see Supporting Figure S13f. This implies a very structurally stable phase upon cycling.
To examine the charge compensation processes which accompany these structural changes on electrochemical cycles, X-ray absorption spectroscopy (XAS) spectra was collected from pristine and cycled materials at the Mn K-edge region. For as-prepared samples, the profiles of Mn K-edge spectra are identical for both orthorhombic and heat-treated samples, as shown in Figure 3c, indicating that the samples contain trivalent Mn ions with a high-spin configuration (t2g3). After delithiation from heat-treated LiMnO2, a clear shift of the K-edge XAS spectrum to a higher energy region indicates the oxidation of Mn to a tetravalent state. Although its profile is slightly different from that of Li2MnO3 with tetravalent Mn ions, this trend originates from the fact that many vacant octahedral sites around Mn ions for the charged sample influences X-ray absorption processes by Mn ions. (31) The energy of the K edge returns upon discharge, indicating reversible Li insertion-extraction processes coupled with cationic Mn3+/Mn4+ redox. Good reversibility is noted after 5 cycles, which is different from the observation for the Li-rich Mn-based system. Unstable oxygen redox is used for the Li-rich system, which often results in continuous reduction of Mn (Co) ions to lower oxidation states. (10,32) The reversibility of Mn oxidation states is also consistent with stable cycling without voltage decay for heat-treated LiMnO2 (Figure 2d and Supporting Figure S8).
Changes in cation arrangements for heat-treated LiMnO2 with electrochemical cycling (after 5 cycles) were directly visualized by HAADF/ABF-STEM observation (Figure 3d and Supporting Figure S14a). Complex cation arrangements are noted after cycling. The sample contains nanosized domains that are about 5–20 nm in size with enriched domain boundaries, consistent with previous work. (33) As shown in Supporting Figure S14a, “point a”, a clear cation arrangement related to a spinel-type host structure, as also highlighted in Figure 3d, it is found. In the ABF image, in which lighter ions are clearly visualized, the presence of ions is noted at tetrahedral sites (“point 1–A” in Figure 3d), and these ions are expected to be lighter Li ions in the spinel structure. When compared with heat-treated LiMnO2, smaller and nonuniform nanosized domains are found for orthorhombic LiMnO2 after cycling (Supporting Figure S14b), which is consistent with a previous finding. (19) However, it is also difficult to conclude that all nanosized domains have spinel-type cation arrangements. In “point 2” in Figure 3d, and “point b” in Supporting Figure S14a, layered domains with a clear contrast in alternate octahedral layers are found. The presence of ions between two octahedral layers is also noted in the HAADF image, in which heavier ions are more emphasized. This phase is therefore regarded as a partially Mn ordered layered phase. Note that similar layered domains are more enriched for the sample derived from monoclinic layered LiMnO2 (Supporting Figure S14c). Additionally, in “point 1-B” in Figure 3d, and “point c” in Supporting Figure S14a, some domains show that all octahedral sites have uniform contrast, suggesting that Mn disordered rocksalt domains are also present.

Factors Affecting the Phase Transition to a Spinel-Related Structure

The increase in reversible capacity on electrochemical cycling (Figure 2a) coupled with structural evolution studied by synchrotron XRD (Figure 3a) reveals that phase transition processes and their kinetics depend on the crystal structures in the as-prepared samples. Among the tested samples, α-NaFeO2-type monoclinic LiMnO2 shows the fastest phase transition with relatively higher crystallinity, whereas the slowest phase transition and the increase in reversible capacities for the initial several cycles are evidenced for orthorhombic LiMnO2. Heat-treated LiMnO2, with both domains, showed intermediate behavior. The kinetics of phase transition would be expected to be influenced by the cation distribution in the original phases. Note that both orthorhombic and monoclinic LiMnO2 have a common packing for oxide ions, i.e., cubic close-packed structure, and a difference is found for cation arrangements at octahedral sites. The spinel-type framework structure also features the same oxygen packing regime. Therefore, phase transitions from orthorhombic/monoclinic LiMnO2 to spinel LixMnO2 are ideally achieved only by cation migration. If 1/4 of Mn ions in MnO2 slab in monoclinic LiMnO2 cooperatively migrate into adjacent octahedral sites in Li layers, (34) a monoclinic layered to spinel phase transition occurs as shown in Figure 4a (also see Supporting Figure S1c). In contrast, the migration of 50% of Mn ions are required for the orthorhombic to spinel-like phase formation. (35) This fact clearly influences the kinetics of phase transition, and therefore, the phase transition and lower crystallinity phase are only observed after cycling for orthorhombic LiMnO2.

Figure 4

Figure 4. Phase evolution on electrochemical cycles for different LiMnO2 polymorphs: (a) Schematic illustrations for phase transition processes and computational study for phase transition for delithiated phases (also see Supporting Figure S1c), with (b)–(d) showing the monoclinic-derived Li0.5MnO2, (e)–(f) the orthorhombic-derived Li0.5MnO2 and (g) comparison of stability with molecular dynamics simulations.

High Resolution Image
Download MS PowerPoint Slide
To further study phase transition kinetics, molecular dynamics calculations were performed on Li0.5MnO2 derived from orthorhombic/monoclinic LiMnO2 using the Universal Neural Network Potential (UNNP). The UNNP learns using a deep neural network approach from the results of first-principles DFT calculations performed on various compositions and structures. This enables the computation of large-scale models while maintaining the accuracy of DFT calculations. (36) The validity of this approach was evaluated by comparing the calculation results from both large-scale first-principles calculations and the UNNP. Supporting Figure S15 is a diagnostic plot for the energies and force components (in x, y, and z directions) acting on each ion obtained from both DFT and UNNP calculations. Because the coefficient of determination and the slopes are close to 1 for both energies and forces, UNNP sufficiently reproduces DFT calculations for the Li0.5MnO2 composition. Figures 4b–f shows snapshots of crystal structures after 1 ns of NPT-MD calculations for Li0.5MnO2, derived from monoclinic layered and orthorhombic LiMnO2. In the monoclinically derived Li0.5MnO2, three Mn ions in the octahedral sites migrate to the tetrahedral sites in the Li layer at 300 K (Figure 4b). At 500 K, the number of Mn ions located at the tetrahedral sites increases to six (Figure 4c). Moreover, a dumbbell configuration is observed, in which Li-vacancy-Mn atoms are arranged in the tetrahedral, octahedral, and tetrahedral sites in the direction perpendicular to the layer, shown in Figure 4d. This cation arrangement is consistent with the mechanism of Mn ion migration proposed by Reed et al. using first-principles DFT calculations. (37,38) Multivalent ions are generally believed to have low diffusivity within oxide lattices, but divalent Mn ions formed by disproportionation reaction of Mn3+ move even at room temperature in conjunction with Li ions according to the literature. (37) This behavior leads to the phase transition during electrochemical cycling; however, if the migration requires Mn2+ the propensity of such a transition would be limited to when Mn2+ is both high in concentration in the crystal structure and located near the planar defects discussed above. In contrast, no changes are observed in the host structure of Li0.5MnO2 derived from orthorhombic LiMnO2 at 300 and 500 K, confirming that the host structure is preserved (Figure 4e and f). This fact indicates that the diffusivity of Mn ions in the orthorhombic structure is qualitatively lower than that in the monoclinic structure and changes in the MnO2 structural framework are suppressed. Figure 4g shows changes in the number of Mn ions occupying the tetrahedral sites during the MD calculation process. As suggested in Figure 4e and f, there are no Mn ions moving to tetrahedral sites throughout the 1 ns simulation time in Li0.5MnO2 with an orthorhombic structure. On the other hand, the number of Mn ions occupying tetrahedral sites increases almost monotonically over time in Li0.5MnO2 with the monoclinic layered structure. (In the MD simulation at 500 K, some of Mn ions move back from tetrahedral sites temporarily to octahedral sites but quickly return to tetrahedral sites depending on the time scale of the calculation.) This movement of Mn does not show any sign of saturation, thus MD structure after 1 ns is not considered to be at equilibrium. Hence, it may continuously change from the layered structure to the more stable spinel phase. Very recently, Deng et al. conducted NPT-MD calculations on Li0.5MnO2 with an orthorhombic structure using a UNNP. (39) At a high temperature of 1100 K, a phase transition from the orthorhombic structure to the spinel-type arrangement was found, further agreeing with our findings. By evaluating the changes in the XRD diffraction profile over time for the structures output by MD, the transition to the spinel phase was estimated to be around 0.8 ns at 1100 K. From these results, it is concluded that a phase transition is occurring due to a phenomenon where the constituent ions move simultaneously or cooperatively. As no movement of Mn ions is found in the MD calculations below 500 K within 1 ns in the orthorhombic structure, it further highlights that the phase transitions are relatively slow for the orthorhombic structure, correlating with the results shown in Figures 2 and 3.

Practical Assessment of Nanostructured LiMnO2 for Battery Applications

Detailed analysis for three LiMnO2 polymorphs reveals that the difference in the original crystal structures influences phase transition kinetics and phase crystallinity after electrochemical cycling, but no correlation with electrode reversibility and voltage hysteresis is noted. Nevertheless, as shown in Figure 1b and Supporting Figure S1, another important difference for these samples is found in grain sizes. Heat-treated LiMnO2 has a small particle size, <100 nm with good uniformity, which originates from the morphological character of the precursor, nanosized rocksalt LiMnO2 synthesized by high-energy milling. This fact also suggests that LiMnO2 with good electrode reversibility can be synthesized without high-energy milling and the precursor rocksalt LiMnO2 through particle size engineering. To test this hypothesis, we directly synthesized nanostructured LiMnO2 by using a simple calcination approach. Mn2O3 was thoroughly mixed with LiOH·H2O, a highly reactive precursor with a lower melting point compared with Li2CO3. The mixture of Mn2O3 and LiOH·H2O was pelletized and heated at 200 °C in an inert atmosphere to remove water. After water was removed, the temperature of the furnace was increased from 200 to 700 °C with a ramp-up rate of 10 °C min–1. After reaching the temperature to 700 °C, the furnace was immediately cooled to room temperature at a rate of 4 °C min–1. Note, the sample was heated inside Cu foil to avoid the oxidation and the detailed methodology has been described in the literature for similar materials. (40) An XRD pattern and SEM image of the synthesized sample are shown in Supporting Figure S16a and b, respectively. As shown in Supporting Figure S16a, this sample is crystallographically similar to the sample derived from metastable rocksalt LiMnO2. Furthermore, its grain size is small (Figure 5a and Supporting Figure S16b), and moreover, the sample delivers a large reversible capacity, ∼230 mA h g–1 at a rate of 10 mA g–1 with 2.2 V discharge cutoff (Figure 5b). The surface area of the sample was measured to be 4.4 m2 g–1 by the BET method, which is comparable to the surface area (5.1 m2 g–1) observed for heat-treated LiMnO2 derived from the LiMnO2 rocksalt precursor. This alternative synthesis route is cost-effective and significantly simpler and produces a structure similar to that of heat-treated LiMnO2 with monoclinic and orthorhombic domains.

Figure 5

Figure 5. Direct synthesis and electrode performance of “nanostructured LiMnO2”: (a) A scheme of the synthesis of nanostructured LiMnO2 and lithium phosphate coating. Synchrotron XRD data and STEM/EDX data of lithium phosphate coated LiMnO2. (b) Galvanostatic charge/discharge curves of nanostructured LiMnO2 at a rate of 10 mA g–1, (c) capacity and energy density retention of lithium phosphate coated LiMnO2 in conventional electrolyte and highly concentrated electrolyte solutions at a rate of 25 mA g–1, (d) Mn 2p XPS spectra of metallic Li electrodes after cycling in different electrolyte solutions, and (e) discharge/charge rate capability of lithium phosphate coated LiMnO2 in the conventional electrolyte solution.

High Resolution Image
Download MS PowerPoint Slide
Practically, the dissolution of Mn ions into electrolyte solution is known as a significant problem for Mn-based electrode materials. (41) Therefore, two methodologies were further applied; (1) surface coating by “phosphate” ions and (2) the use of a highly concentrated electrolyte solution. Lithium phosphate is less soluble in polar solvents and the elimination of free-solvent in highly concentrated electrolyte solutions results in the lower solubility of electrode materials. (13) The coating of lithium phosphate has been conducted by using the methodology reported in literature. (42) As shown in Figure 5a, after the coating by lithium phosphate, the presence of phosphate ions on the particle of LiMnO2 is evidenced by FE-SEM/EDX observation. A trace of crystalline lithium phosphate is also found by synchrotron XRD data (Figure 5a and Supporting Figure S16a). Although a similar initial capacity is observed for LiMnO2 before/after coating (Supporting Figure S16c), improved capacity retention is achieved for the coated sample (Supporting Information, Figure S16d) in conventional electrolytes. However, capacity is gradually lost with cycling to 60 cycles, and further degradation of the reversibility is observed after 60 cycles. This originates from the dissolution of the Mn ions from LiMnO2 and the accumulation of Mn ions on the metallic Li electrode. Electrolyte decomposition cannot be avoided when Mn ions are deposited on the surface of negative electrodes. (43) Indeed, clear evidence of Mn ion deposition on the surface of metallic Li is noted by XPS (Figure 5d).
Electrode reversibility of LiMnO2 is significantly improved by using highly concentrated electrolyte solution with Li(NSO2F)2 (LiFSA) and dimethyl carbonate (DMC), and 5.5 M LiFSA/DMC. (44) The maximum reversible capacity of ∼220 mA h g–1 at a rate of 25 mA g–1 after 10 cycles is found, and 90% of this capacity is retained even after 100 cycles (Figure 5c). The energy density reaches 730 Wh kg–1 at the 10th cycle, and 660 Wh kg–1 is retained at the 100th cycle. Improved Coulombic efficiency (99.5% on average) is also noted with 5.5 M LiFSA/DMC when compared with the conventional electrolyte (98.3% on average from 10 to 55 cycles). The electrochemical data of noncoated LiMnO2 with 5.5 M LiFSA/DMC is also shown in Supporting Figure S16e, and 83% capacity retention is achieved after 100 cycles. Note, Mn ions on the surface of metallic Li electrode cycled in 5.5 M LiFSA/DMC are not detected via XPS (Figure 5d), indicating that the dissolution of Mn ions is effectively suppressed with the highly concentrated electrolyte solution. Moreover, excellent quick charge capability is also found, Figure 5e, and approximately 75% of the capacity is recharged at a rate of 1000 mA g–1. These facts indicate the high practical potential of LiMnO2 coated with lithium phosphate. Further improvement of electrode reversibility is anticipated through mitigation of Mn dissolution on electrochemical cycling.

Conclusions

Click to copy section linkSection link copied!
Three different LiMnO2 polymorphs are synthesized, thermodynamically stable orthorhombic phase, metastable monoclinic layered phase derived from NaMnO2, and a phase with both orthorhombic and monoclinic domains derived from rocksalt LiMnO2. Electrode performance of these polymorphs has been systematically compared, and detailed analysis of differences in reaction mechanisms reveals that (1) the monoclinic layered domain effectively activates structural transition to the spinel-like phase, associated with structural similarity for monoclinic layered and spine-type structures, and (2) the surface area of particles influences reversible capacities and voltage hysteresis on electrochemical cycles. From these findings, nanostructured LiMnO2 with domain structures has been directly synthesized from LiOH·H2O and Mn2O3 without the use of metastable precursors. Moreover, nanostructured LiMnO2 shows a higher energy density, which is competitive with Ni-enriched electrode materials used for state-of-the-art electric vehicles. Voltage decay associated with oxygen loss, as observed for Li2MnO3-based electrode materials, cannot be observed. The sample also provides excellent fast charge ability, which is an essential character for electric vehicle applications. Although a remaining practical problem was found in Mn dissolution and capacity loss on electrochemical cycles, this problem is also effectively mitigated by the use of a highly concentrated electrolyte solution coupled with lithium phosphate coating. These findings contribute the development of high-energy, low-cost, and sustainable positive electrode made from abundant Mn sources without Ni/Co, which potentially realizes the sustainable energy society without the dependence on fossil fuel in the future.

Experimental Methods

Click to copy section linkSection link copied!

Synthesis of Materials

Orthorhombic LiMnO2 was prepared from Li2CO3 (98.5%, Kanto Kagaku) and Mn2O3 at 900 °C for 12 h in an Ar atmosphere. Excess Li2CO3 (3%) was used to compensate for verbalized Li ions on heating. Mn2O3 was obtained by heating MnCO3 (Kishida Chemical Co., Ltd.) in air. Metastable cubic rocksalt LiMnO2 was prepared by mechanical milling using a planetary ball mill (PULVERISETTE 7; FRITSCH). (21) Orthorhombic LiMnO2 was used as a precursor for the mechanical milling. LiMnO2 (1.5 g) was mixed using a zirconia pot (45 mL) and zirconia balls (15.5 g) at 600 rpm for 12 h. After being milled for 12 h, the mixture was taken out from the container and mixed with a mortar and pestle to ensure sample uniformity during the milling. The mixture was again milled using a zirconia pot and balls at 600 rpm for 12 h. This process was repeated three times, and the mixture was milled for 36 h in total. Monoclinic layered LiMnO2 was prepared by ion-exchange from NaMnO2. NaMnO2 was added into LiBr dissolved in hexanol, and then heated at 160 °C for 96 h. (45) After heating in hexanol, the ion-exchanged sample was filtered and dried. NaMnO2 was synthesized from Na2CO3 (99.5%; Wako Pure Chemical Industries, Ltd.) and Mn2O3 at 800 °C for 8 h in an Ar atmosphere. Heat-treated LiMnO2 was obtained by heat-treatment of cubic rocksalt LiMnO2 at 700 °C for 2 h in Ar atmosphere. The synthesized LiMnO2 polymorphs were stored in a desiccator in air with silica gel.

Electrochemical Evaluations

The electrode performance of orthorhombic LiMnO2, cubic rocksalt LiMnO2, and monoclinic layered LiMnO2 was examined for the carbon composite samples prepared by ball milling. The samples were mixed with acetylene black, AB (HS-100; Denka Co., Ltd., LiMnO2:AB = 90:10 wt %) by using the planetary ball mill at 300 rpm for 12 h with the zirconia container and balls. Composite positive electrodes, comprising 76.5 wt % LiMnO2, 13.5 wt % AB, and 10 wt % poly(vinylidene fluoride), PVdF (KF 1100; Kureha Co. Ltd.), were pasted on aluminum foil as a current collector. Electrode performance of heat-treated LiMnO2 was evaluated without the preparation of a carbon composited sample, and a mixture of 80.0 wt % LiMnO2, 10.0 wt % AB, and 10.0 wt % PVdF was pasted on aluminum foil. Typical thickness of the composite electrode is 60 ± 10 μm, and the loading of active materials ranges from 3–4 mg cm–2. The composite electrode was evaluated without calendaring.
The electrodes were dried at 80 °C for 2 h in vacuum and then heated at 120 °C for 2 h. Metallic lithium (Honjo Metal Co., Ltd.) with a 250 μm thickness was used as a negative electrode. The electrolyte solution used was 1.0 mol dm–3 LiPF6 dissolved in ethylene carbonate (EC): dimethyl carbonate (DMC) with a volume ratio of 3:7, battery grade; Kishida Chemical Corp., Ltd.), and 300 μL of electrolyte solution was added for each electrochemical cell. Conventional polyolefin separator was used as the separator. LiN(SO2F)2 (LiFSA) dissolved in DMC was also used (LiFSA: DMC = 1:1.1 in molar ratio, battery grade; Kishida Chemical Corp., Ltd.) with aramid-coated polyolefin separator. (46,47) Two-electrode cells (TJ-AC; Tomcell Japan) were assembled in an Ar-filled glovebox. An Al cell was used for a positive electrode side to avoid corrosion of cells made of stainless steel. (48) The cells were cycled at a rate of 10 or 25 mA g–1 at room temperature.

Lithium Phosphate Coating

LiMnO2 (0.5 g) was added into ethanol (10 mL), and then lithium acetate (Wako Pure Chemical Industries, Ltd.) ethanol solution (275 μL, 0.047 mol L–1) was added. Phosphoric acid (Wako Pure Chemical Industries, Ltd.) ethanol solution (122 μL, 0.060 mol L–1) was further added under stirring. The mixed solution was dried in vacuum, and the obtained powder was heated at 300 °C for 5 h in air.

Material Characterization

Phase purity and crystal structures of the obtained samples were examined by using an X-ray diffractometer (D2 PHASER, Bruker) equipped with a high-speed one-dimensional detector. Nonmonochromatized Cu Kα radiation was utilized as an X-ray source with a nickel filter. Structural analysis was conducted using RIETAN-FP software. (49) The reaction mechanisms of the electrode materials during cycling were examined by ex-situ SXRD (SPring-8, BL19B2) and hard X-ray absorption spectroscopy (Photon Factory, BL-9C) at the V K-edge. Composite electrode materials for these measurements were extracted from two-electrode cells after cycling at a rate of 10 mA g–1, and then rinsed with dimethyl carbonate. After being dried, the samples were packed into a capillary tube and sealed in a water-resistant polymer film in an argon-filled glovebox. The hard X-ray absorption spectra were collected with a silicon monochromator in the transmission mode. The intensity of the incident and transmitted X-rays was measured using an ionization chamber at room temperature. Normalization of the XAS spectra was conducted using the program code IFEFFIT. (50) The background was determined by using a cubic spline procedure. Synchrotron X-ray diffraction study was also performed at the BL5S2 of Aichi Synchrotron Radiation Center.
Operando SXRD data were also collected using the Powder Diffraction Beamline at the Australian Synchrotron, (51) using a wavelength λ = 0.727657(7) Å determined using a National Institute of Standards and Technology (NIST) 660b LaB6 standard reference material. Samples were cycled in Li half-cells by using CR2032 coin cell casings. A 3 mm hole was drilled through the cell casings and sealed using Kapton tape to allow for transmission of the incident beam through the sample. Diffraction data were collected in 6 min intervals while the cell was cycled from 1.5 to 4.8 V and this process was repeated for 2.5 cycles.
X-ray total scattering measurements was performed with an incident X-ray energy of E = 61.4 keV at the BL04B2 beamline in SPring-8, Japan, to study the local structure by pair distribution function (PDF) analysis. Hybrid detectors of Ge and CdTe were employed for the data collection of total structure factor S(Q). The reduced PDF G(r) was obtained by the conventional Fourier transform of S(Q). (52)
Scanning transmission electron microscopy (STEM) was conducted using a JEOL JEM-ARM200F with a CEOS CESCOR STEM Cs corrector (spherical aberration corrector) operated at an acceleration voltage of 200 kV. Details for experimental setup, including specimen preparation, are found in literature. (53) Particle morphologies of the samples were observed using a scanning electron microscope (SEM; SU8010, Hitachi High-Technologies).
X-ray photoelectron spectroscopy (XPS) analysis of the metallic Li electrode was conducted with a PHI Quantera SXM spectrometer (Ulvac-phi). Electrochemical cells after 25 cycles were disassembled in the Ar-filled glovebox. Metallic Li electrodes obtained from the cells were rinsed with DMC and dried under vacuum, and then, the samples were transferred into the XPS instrument using an airtight transfer vessel without exposure to air. XPS measurements were conducted with an X-ray source (Al Kα) under a base pressure of 6.7 × 10–8 Pa.
The Brunauer–Emmett–Teller (BET) specific surface area of the samples was measured at 77 K on a micromeritics surface area and porosity analyzer (BELSORP MINI X; Microtrac MRB).

Theoretical Analysis

Molecular dynamics calculations were performed using the Universal Neural Network Potential (UNNP). In this study, version 4.0.0 of the Preferred Potential (PFP) potential set implemented in the Matlantis software was used for the calculation. (54) The validity of UNNP was evaluated by comparing the calculation results evaluated with first-principles calculations and UNNP. The models used for accuracy comparison were the structures of Li18Mn36O72 with layered and orthorhombic ordering. The structures were relaxed using first-principles calculations (DFT), and then distortions were introduced by randomly displacing the constituent atoms to create 50 structures for each structure (a total of 100 distorted structures are made). In detail, models were created by randomly displacing lattice constants by <0.1 Å, lattice angles by <2 degrees, and atomic positions within 0.05 Å. Energy calculations were performed on these models using both DFT and UNNP. First-principles calculations were performed using the Vienna ab initio simulation package (VASP) (55,56) with the projector augmented-wave method (PAW). (57) The Perdew–Burke–Ernzerhof functional (revised for solids) generalized gradient approximation (PBEsol-GGA) were used as the exchange-correlation functional. (58,59) Also, the DFT+U method was used, setting the U value for Mn at 3.9 eV, referencing the literature. (60) Molecular dynamics (MD) simulations were conducted on these models under isothermal–isobaric ensemble (NPT) conditions for 1 ns (106 steps). In these MD simulations, superlattice models Li75Mn150O300 and Li60Mn120O240 for layered and orthorhombic ordering structures were created by scaling 5 × 5 × 2 times and 5 × 4 × 3 times, respectively.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acscentsci.4c00578.

  • SEM images of different LiMnO2 polymorphs, highlighted XRD patterns of orthorhombic and heat-treated LiMnO2, comparison of oxygen packing of orthorhombic and monoclinic layered LiMnO2, energy difference of LiMnO2 polymorphs obtained by theoretical calculations, STEM images of heat-treated LiMnO2, simulated XRD patterns with stacking fault analysis, structure factors and X-ray PDFs of different LiMnO2 polymorphs obtained by high-energy X-ray diffraction, charge/discharge curves of orthorhombic LiMnO2 before/after the preparation of carbon composited sample, charge/discharge curves and differential capacity plots of the as-prepared sample for monoclinic layered LiMnO2, cyclability of different LiMnO2 polymorphs at a rate of 10 mA g–1, comparison of electrode performance of heat-treated LiMnO2 and Li1.2Co0.13Ni0.13Mn0.54O2, comparison of quasi-open circuit voltage for heat-treated LiMnO2 (5th and 10th cycles), charge/discharge curves of LiNi0.835Co0.15Al0.015O2, structural evolution of different LiMnO2 polymorphs, simulated XRD patterns of cubic and tetragonal Li2Mn2O4 (Li1+xMn2O4), selected Rietveld-refined fits of structural models to the operando XRD data for heat-treated LiMnO2, selected XRD patterns from the operando XRD experiment, operando XRD pattern overlaid, STEM images of heat-treated LiMnO2 after cycle test, diagnostic plots of energies and forces obtained by DFT and UNNP calculations, characterization and electrochemistry of nanostructured LiMnO2 (PDF)

Terms & Conditions

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

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
    • Naoaki Yabuuchi - Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan;  Advanced Chemical Energy Research Center, Institute of Advanced Sciences, Yokohama National University, Yokohama 240-0067, Japan;  Orcidhttps://orcid.org/0000-0002-9404-5693;  Email: [email protected]
  • Authors
    • Yuka Miyaoka - Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    • Takahito Sato - Department of Applied Chemistry, Tokyo Denki University, 5 Senju Asahi-Cho, Adachi, Tokyo 120-8551, Japan
    • Yuna Oguro - Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
    • Sayaka Kondo - Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
    • Koki Nakano - Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
    • Masanobu Nakayama - Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan;  Orcidhttps://orcid.org/0000-0002-5113-053X
    • Yosuke Ugata - Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan;  Advanced Chemical Energy Research Center, Institute of Advanced Sciences, Yokohama National University, Yokohama 240-0067, Japan;  Orcidhttps://orcid.org/0000-0002-8233-6725
    • Damian Goonetilleke - School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia;  Present Address: Corporate Research and Development, Umicore, 2250 Olen, Belgium;  Orcidhttps://orcid.org/0000-0003-1033-4787
    • Neeraj Sharma - School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia;  Orcidhttps://orcid.org/0000-0003-1197-6343
    • Alexey M. Glushenkov - Research School of Chemistry, The Australian National University, Canberra, ACT 2600, Australia;  Orcidhttps://orcid.org/0000-0002-4851-839X
    • Satoshi Hiroi - Faculty of Materials for Energy, Shimane University, Matsue, Shimane 690-8504, Japan;  Orcidhttps://orcid.org/0000-0001-5058-6757
    • Koji Ohara - Faculty of Materials for Energy, Shimane University, Matsue, Shimane 690-8504, Japan
    • Koji Takada - Tosoh Corporation, 4560 Kaisei-cho, Shunan-Shi, Yamaguchi 746-8501, Japan
    • Yasuhiro Fujii - Tosoh Corporation, 4560 Kaisei-cho, Shunan-Shi, Yamaguchi 746-8501, Japan
  • Author Contributions

    Y.M. and T.S. contributed equally to this work.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

NY acknowledges the partial support from JSPS, Grant-in-Aid for Scientific Research (Grant Numbers 19H05816, 21H04698, and 24H02204). MN and KO thank JSPS (Grant Number 19H05815 and 19H05814). This work was partially supported by JST, CREST Grant Number JPMJCR21O6, Japan and by MEXT Program: Data Creation and Utilization-Type Material Research and Development Project, Grant Number JPMXP1122712807. NY acknowledges the partial support by JST as part of Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE), Grant Number JPMJAP2313. A part of this study was supported by JST, The Green Technologies for Excellence (GteX) Program, Grant Number JPMJGX23S3. NS and DG acknowledge support from the Australian Research Council through the Research Training Program (RTP) and FT200100707. The synchrotron X-ray absorption work was done under the approval of the Photon Factory Program Advisory Committee (Proposal No. 2021G039). The synchrotron radiation experiments were performed at the beamlines BL04B2 and BL19B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal Nos. 2021B1722 and 2023A1001). Synchrotron X-ray diffraction study also performed at the BL5S2 of Aichi Synchrotron Radiation Center (Proposal No. 2022D6042). Operando synchrotron X-ray diffraction studies were performed on the Powder Diffraction beamline at the Australian Synchrotron, operated by the Australian Nuclear Science and Technology Organisation (ANSTO). We thank Dr. Yoshinobu Miyazaki and Dr. Tomohiro Saito from Sumika Chemical Analysis Service, Ltd. for the STEM observation.

References

Click to copy section linkSection link copied!

This article references 61 other publications.

  1. 1
    Ziegler, M. S.; Trancik, J. E. Re-examining rates of lithium-ion battery technology improvement and cost decline. Energy Environ. Sci. 2021, 14, 1635– 1651,  DOI: 10.1039/D0EE02681F
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Olivetti, E. A.; Ceder, G.; Gaustad, G. G.; Fu, X. Lithium-Ion Battery Supply Chain Considerations: Analysis of Potential Bottlenecks in Critical Metals. Joule 2017, 1, 229– 243,  DOI: 10.1016/j.joule.2017.08.019
    Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Vaalma, C.; Buchholz, D.; Weil, M.; Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 2018, 3, 18013,  DOI: 10.1038/natrevmats.2018.13
    Google Scholar
    There is no corresponding record for this reference.
  4. 4
    Aishova, A.; Park, G.-T.; Yoon, C. S.; Sun, Y.-K. Cobalt-Free High-Capacity Ni-Rich Layered Li[Ni0.9Mn0.1]O2 Cathode. Adv. Energy Mater. 2020, 10, 1903179,  DOI: 10.1002/aenm.201903179
    Google Scholar
    4
    Cobalt-Free High-Capacity Ni-Rich Layered Li[Ni0.9Mn0.1]O2 Cathode
    Aishova, Assylzat; Park, Geon-Tae; Yoon, Chong S.; Sun, Yang-Kook
    Advanced Energy Materials (2020), 10 (4), 1903179CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell)
    Li[Ni0.9Co0.1]O2 (NC90), Li[Ni0.9Co0.05Mn0.05]O2 (NCM90), and Li[Ni0.9Mn0.1]O2 (NM90) cathodes are synthesized for the development of a Co-free high-energy-d. cathode. NM90 maintains better cycling stability than the two Co-contg. cathodes, particularly under harsh cycling conditions (a discharge capacity of 236 mAh g-1 with a capacity retention of 88% when cycled at 4.4 V under 30°C and 93% retention when cycled at 4.3 V under 60°C after 100 cycles). The reason for the enhanced stability is mainly the ability of NM90 to absorb the strain assocd. with the abrupt anisotropic lattice contraction/extn. and to suppress the formation of microcracks, in addn. to enhanced chem. stability from the increased presence of stable Mn4+. Although the absence of Co deteriorates the rate capability, this can be overcome as the rate capability of the NM90 approaches that of the NCM90 when cycled at 60°C. The long-term cycling stability of NM90 is confirmed in a full cell, demonstrating that it is one of the most promising Co-free cathodes for high-energy-d. applications. This study not only provides insight into redefining the role of Mn in a Ni-rich cathode, it also represents a clear breakthrough in achieving a com. viable Co-free Ni-rich layered cathode.
  5. 5
    Geng, C.; Liu, A.; Dahn, J. R. Impact of Aluminum Added to Ni-Based Positive Electrode Materials by Dry Particle Fusion. Chem. Mater. 2020, 32, 6097– 6104,  DOI: 10.1021/acs.chemmater.0c01728
    Google Scholar
    5
    Impact of Aluminum Added to Ni-Based Positive Electrode Materials by Dry Particle Fusion
    Geng, Chenxi; Liu, Aaron; Dahn, Jeff R.
    Chemistry of Materials (2020), 32 (14), 6097-6104CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    This work reports two relatively new approaches to synthesize LiNi1-xAlxO2 materials. The first is coating Al2O3 on a Ni(OH)2 precursor by dry particle fusion followed by heating with LiOH·H2O. The second is coating Al2O3 on LiNiO2 by dry particle fusion followed by heating. X-ray diffraction (XRD), cross-sectional SEM (SEM), energy-dispersive spectroscopy (EDS) mapping, and EDS line scans were carried out. Coin-type cells were made to test the electrochem. performance of the synthesized materials. It was shown that Ni(OH)2 coated with 1, 2, and 3% Al2O3 followed by heating with LiOH·H2O had better capacity retention than samples prepd. by coating on LiNiO2 directly. Of all of the samples prepd., Ni(OH)2 coated with 3% Al2O3, followed by heating with LiOH·H2O had the largest specific discharge capacity and the best capacity retention. The reproducibility of this approach was verified by prepg. two more batches of Ni(OH)2 coated with 3% Al2O3 followed by heating with LiOH·H2O in the same way. This work suggests that coating desired materials on precursors by dry particle fusion is an attractive approach for synthesizing next-generation pos. electrode materials.
  6. 6
    Ikeda, N.; Konuma, I.; Rajendra, H. B.; Aida, T.; Yabuuchi, N. Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?. J. Mater. Chem. A 2021, 9, 15963– 15967,  DOI: 10.1039/D1TA03066C
    Google Scholar
    6
    Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?
    Ikeda, Naohiro; Konuma, Itsuki; Rajendra, Hongahally Basappa; Aida, Taira; Yabuuchi, Naoaki
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2021), 9 (29), 15963-15967CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Ni-enriched layered materials are utilized as pos. electrode materials of high-energy Li-ion batteries. Because electrode reversibility is gradually lost for stoichiometric LiNiO2 after continuous cycles, Ni ions are partially substituted by other metal ions (Co, Mn, Al etc.). However, the origin of deterioration in stoichiometric LiNiO2 is still not fully understand yet. Moreover, the loss of capacities is obsd. only in the high voltage region (>4.1 V), which is obviously different from the failure mode obsd. in other electrode materials. Here, we report for the first time the origin of deterioration, which is revealed by an in situ X-ray diffraction study. For fully charged NiO2, Ni ions migrate from original octahedral sites in NiO2 slabs to face-sharing tetrahedral sites in Li layers, by which the O3 to O1 phase transition is suppresed. Note that Ni migration is a reversible process, and the Ni ions migrate back to the original octahedral sites on discharge. However, after continuous cycles, the reversibility of Ni migration is gradually lost, and Ni ions are partially left at the tetrahedral sites in Li layers. Electrode kinetics are also deteriorated because of the Ni occupation in Li layers, and the accumulation of Ni ions at tetrahedral sites results in the loss of reversible capacities in the high voltage region. This finding opens a new way to design high-capacity Ni-enriched electrode materials, leading to the development of high-energy Li-ion batteries.
  7. 7
    Goonetilleke, D.; Riewald, F.; Kondrakov, A. O.; Janek, J.; Brezesinski, T.; Bianchini, M. Alleviating Anisotropic Volume Variation at Comparable Li Utilization during Cycling of Ni-Rich, Co-Free Layered Oxide Cathode Materials. J. Phys. Chem. C 2022, 126, 16952– 16964,  DOI: 10.1021/acs.jpcc.2c04946
    Google Scholar
    7
    Alleviating Anisotropic Volume Variation at Comparable Li Utilization during Cycling of Ni-Rich, Co-Free Layered Oxide Cathode Materials
    Goonetilleke, Damian; Riewald, Felix; Kondrakov, Aleksandr O.; Janek, Juergen; Brezesinski, Torsten; Bianchini, Matteo
    Journal of Physical Chemistry C (2022), 126 (40), 16952-16964CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Driven by demand for greater energy densities, Ni-rich cathode materials, such as lithium nickel cobalt manganese (NCM) and nickel cobalt aluminum (NCA) oxides, with compns. approaching the lithium nickel oxide (LiNiO2) end-member have been investigated intensively. While such compns. are targeted assuming the redox activity of nickel will lead to higher capacities, the role of even small amts. of Mn and Co in these systems is of great importance. To raise considerations about the role of Mn and Co, operando X-ray diffraction has been used to resolve the structure-electrochem. relationships in a series of Ni-rich NMX (LiNi1-yMnyO2, y = 0.25, 0.17, 0.10, 0.05) cathode materials. To ensure a meaningful comparison, the upper cutoff potential was varied as a function of the Mn content in the material to ensure comparable states of delithiation and thereby provide a capacity-normalized comparison of the structural evolution. During the first cycle all materials deliver a specific charge capacity exceeding 230 mAh g-1, corresponding to a residual Li content of x(Li) ≈ 0.15, and exhibit a structural evolution free of any first-order phase transitions. Monitoring the structural parameters of the materials during cycling shows that Mn substitution substantially reduces the magnitude of expansion/contraction of lattice parameters even when comparable amts. of Li are removed from the structure and more significantly also reduces the anisotropy of the vol. changes. Thus, these Co-free, Ni-rich materials hold promise as high-capacity cathodes with good structural and mech. stability.
  8. 8
    Konuma, I.; Ikeda, N.; Campéon, B. D. L.; Fujimura, H.; Kikkawa, J.; Luong, H. D.; Tateyama, Y.; Ugata, Y.; Yonemura, M.; Ishigaki, T.; Aida, T.; Yabuuchi, N. Unified understanding and mitigation of detrimental phase transition in cobalt-free LiNiO2. Energy Storage Mater. 2024, 66, 103200,  DOI: 10.1016/j.ensm.2024.103200
    Google Scholar
    There is no corresponding record for this reference.
  9. 9
    Mauler, L.; Lou, X.; Duffner, F.; Leker, J. Technological innovation vs. tightening raw material markets: falling battery costs put at risk. Energy Advances 2022, 1, 136– 145,  DOI: 10.1039/D1YA00052G
    Google Scholar
    There is no corresponding record for this reference.
  10. 10
    Hu, E.; Yu, X.; Lin, R.; Bi, X.; Lu, J.; Bak, S.; Nam, K.-W.; Xin, H. L.; Jaye, C.; Fischer, D. A.; Amine, K.; Yang, X.-Q. Evolution of redox couples in Li- and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release. Nat. Energy 2018, 3, 690– 698,  DOI: 10.1038/s41560-018-0207-z
    Google Scholar
    10
    Evolution of redox couples in Li- and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release
    Hu, Enyuan; Yu, Xiqian; Lin, Ruoqian; Bi, Xuanxuan; Lu, Jun; Bak, Seongmin; Nam, Kyung-Wan; Xin, Huolin L.; Jaye, Cherno; Fischer, Daniel A.; Amine, Kahlil; Yang, Xiao-Qing
    Nature Energy (2018), 3 (8), 690-698CODEN: NEANFD; ISSN:2058-7546. (Nature Research)
    Voltage fade is a major problem in battery applications for high-energy lithium- and manganese-rich (LMR) layered materials. As a result of the complexity of the LMR structure, the voltage fade mechanism is not well understood. Here we conduct both in situ and ex situ studies on a typical LMR material (Li1.2Ni0.15Co0.1Mn0.55O2) during charge-discharge cycling, using multi-length-scale X-ray spectroscopic and three-dimensional electron microscopic imaging techniques. Through probing from the surface to the bulk, and from individual to whole ensembles of particles, we show that the av. valence state of each type of transition metal cation is continuously reduced, which is attributed to oxygen release from the LMR material. Such redns. activate the lower-voltage Mn3+/Mn4+ and Co2+/Co3+ redox couples in addn. to the original redox couples including Ni2+/Ni3+, Ni3+/Ni4+ and O2-/O-, directly leading to the voltage fade. We also show that the oxygen release causes microstructural defects such as the formation of large pores within particles, which also contributes to the voltage fade. Surface coating and modification methods are suggested to be effective in suppressing the voltage fade through reducing the oxygen release.
  11. 11
    Kobayashi, Y.; Sawamura, M.; Kondo, S.; Harada, M.; Noda, Y.; Nakayama, M.; Kobayakawa, S.; Zhao, W.; Nakao, A.; Yasui, A.; Rajendra, H. B.; Yamanaka, K.; Ohta, T.; Yabuuchi, N. Activation and stabilization mechanisms of anionic redox for Li storage applications: Joint experimental and theoretical study on Li2TiO3-LiMnO2 binary system. Mater. Today 2020, 37, 43– 55,  DOI: 10.1016/j.mattod.2020.03.002
    Google Scholar
    11
    Activation and stabilization mechanisms of anionic redox for Li storage applications: Joint experimental and theoretical study on Li2TiO3-LiMnO2 binary system
    Kobayashi, Yuki; Sawamura, Miho; Kondo, Sayaka; Harada, Maho; Noda, Yusuke; Nakayama, Masanobu; Kobayakawa, Sho; Zhao, Wenwen; Nakao, Aiko; Yasui, Akira; Rajendra, Hongahally Basappa; Yamanaka, Keisuke; Ohta, Toshiaki; Yabuuchi, Naoaki
    Materials Today (Oxford, United Kingdom) (2020), 37 (), 43-55CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)
    A binary system of Li2TiO3-LiMnO2 is systematically examd. by joint exptl. and theor. studies as electrode materials for Li storage applications. Increase in a fraction of Li2TiO3 effectively activates anionic redox, and thus holes are reversibly formed on oxygen by electrochem. oxidn. Such holes are energetically stabilized through π-type interaction with Mn t2g orbital as suggested by theor. calcn. However, excess enrichment of Li2TiO3 fractions in this binary system results in the oxygen loss as an irreversible process on delithiation because of a non-bonding character for Ti-O bonds coupled with the formation of O-O dimers, which are chem. and electrochem. unstable species. Detailed electrochem. study clearly shows that Li migration kinetics is relatively slow, presumably coupled with low electronic cond. Nevertheless, nanosizing of primary particles is an effective strategy to overcome this limitation. The nanosized sample prepd. by mech. milling delivers a large reversible capacity, ∼300 mA h g-1, even at room temp. and shows much improved capacity retention. Formation and stabilization of holes for the nanosized sample are also directly evidenced by soft X-ray absorption spectroscopy. From these results, factors affecting the reversibility of anionic redox as emerging new chem. and its possibility for energy storage applications are discussed in more details.
  12. 12
    Ji, H.; Wu, J.; Cai, Z.; Liu, J.; Kwon, D.-H.; Kim, H.; Urban, A.; Papp, J. K.; Foley, E.; Tian, Y.; Balasubramanian, M.; Kim, H.; Clément, R. J.; McCloskey, B. D.; Yang, W.; Ceder, G. Ultrahigh power and energy density in partially ordered lithium-ion cathode materials. Nat. Energy 2020, 5, 213– 221,  DOI: 10.1038/s41560-020-0573-1
    Google Scholar
    12
    Ultrahigh power and energy density in partially ordered lithium-ion cathode materials
    Ji, Huiwen; Wu, Jinpeng; Cai, Zijian; Liu, Jue; Kwon, Deok-Hwang; Kim, Hyunchul; Urban, Alexander; Papp, Joseph K.; Foley, Emily; Tian, Yaosen; Balasubramanian, Mahalingam; Kim, Haegyeom; Clement, Raphaele J.; McCloskey, Bryan D.; Yang, Wanli; Ceder, Gerbrand
    Nature Energy (2020), 5 (3), 213-221CODEN: NEANFD; ISSN:2058-7546. (Nature Research)
    The rapid market growth of rechargeable batteries requires electrode materials that combine high power and energy and are made from earth-abundant elements. Here we show that combining a partial spinel-like cation order and substantial lithium excess enables both dense and fast energy storage. Cation overstoichiometry and the resulting partial order is used to eliminate the phase transitions typical of ordered spinels and enable a larger practical capacity, while lithium excess is synergistically used with fluorine substitution to create a high lithium mobility. With this strategy, we achieved specific energies greater than 1,100 Wh kg-1 and discharge rates up to 20 A g-1. Remarkably, the cathode materials thus obtained from inexpensive manganese present a rare case wherein an excellent rate capability coexists with a reversible oxygen redox activity. Our work shows the potential for designing cathode materials in the vast space between fully ordered and disordered compds.
  13. 13
    Kanno, A.; Ugata, Y.; Ikeuchi, I.; Hibino, M.; Nakura, K.; Miyaoka, Y.; Kawamura, I.; Shibata, D.; Ohta, T.; Yabuuchi, N. Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li2MnO1.5F1.5. ACS Energy Lett. 2023, 8, 2753– 2761,  DOI: 10.1021/acsenergylett.3c00372
    Google Scholar
    There is no corresponding record for this reference.
  14. 14
    Reimers, J. N.; Fuller, E. W.; Rossen, E.; Dahn, J. R. Synthesis and Electrochemical Studies of LiMnO2 Prepared at Low Temperatures. J. Electrochem. Soc. 1993, 140, 3396– 3401,  DOI: 10.1149/1.2221101
    Google Scholar
    14
    Synthesis and electrochemical studies of LiMnO2 prepared at low temperatures
    Reimers, J. N.; Fuller, Eric W.; Rossen, Erik; Dahn, J. R.
    Journal of the Electrochemical Society (1993), 140 (12), 3396-401CODEN: JESOAN; ISSN:0013-4651.
    A new form of LiMnO2, which has recently been shown to reversibly intercalate lithium, has many advantages over other popular lithium-ion battery cathode materials. The authors describe improvements in the previously reported low temp. (300-450°) synthesis and report a new synthesis route based on ion exchange which takes place at 100°. Electrochem. performance is shown to be strongly dependent on synthesis temp. In situ x-ray diffraction and long time cycling measurements indicate that an irreversible structural transformation to disordered spinel takes place when Li is removed from LiMnO2. Nevertheless, the specific capacity of this material is over 190 mAh/g between 2.5 and 4.2 V.
  15. 15
    Armstrong, A. R.; Bruce, P. G. Synthesis of layered LiMnO2 as an electrode for rechargeable lithium batteries. Nature 1996, 381, 499– 500,  DOI: 10.1038/381499a0
    Google Scholar
    15
    Synthesis of layered LiMnO2 as an electrode for rechargeable lithium batteries
    Armstrong, A. Robert; Bruce, Peter G.
    Nature (London) (1996), 381 (6582), 499-500CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)
    We report the synthesis and electrochem. performance of a new material, layered LiMnO2, which is structurally analogous to LiCoO2 for rechargeable lithium batteries. The charge capacity of LiMnO2 (∼270 mA h g-1) compares well with that of both LiCoO2 and LiMn2O4, and preliminary results indicate good stability over repeated charge-discharge cycles.
  16. 16
    Capitaine, F.; Gravereau, P.; Delmas, C. A new variety of LiMnO2 with a layered structure. Solid State Ion. 1996, 89, 197– 202,  DOI: 10.1016/0167-2738(96)00369-4
    Google Scholar
    16
    A new variety of LiMnO2 with a layered structure
    Capitaine, F.; Gravereau, P.; Delmas, C.
    Solid State Ionics (1996), 89 (3,4), 197-202CODEN: SSIOD3; ISSN:0167-2738. (Elsevier)
    A new variety of LiMnO2 exhibiting a layered structure was obtained by chimie douce reaction from α-NaMnO2. This material crystallizes in the monoclinic system. Rietveld refinement of the x-ray diffraction pattern shows clearly that the MnO6 octahedra are strongly distorted, as the result of the Jahn-Teller effect on the trivalent Mn ions. Also, a small amt. of Mn is present within the Li layer, contrary to the α-NaMnO2 precursor phase which exhibits a strictly bidimensional structure. The thermal stability of LiMnO2 was studied by differential scanning calorimetry and by high temp. x-ray diffraction.
  17. 17
    Ohzuku, T.; Kitano, S.; Iwanaga, M.; Matsuno, H.; Ueda, A. Comparative study of Li[LixMn2 - xO4 and LT-LiMnO2 for lithium-ion batteries. J. Power Sources 1997, 68, 646– 651,  DOI: 10.1016/S0378-7753(96)02573-6
    Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Ma, J.; Liu, T.; Ma, J.; Zhang, C.; Yang, J. Progress, Challenge, and Prospect of LiMnO2: An Adventure toward High-Energy and Low-Cost Li-Ion Batteries. Adv. Sci. 2024, 11, 2304938,  DOI: 10.1002/advs.202304938
    Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Jang, Y. I.; Huang, B.; Wang, H.; Sadoway, D. R.; Chiang, Y. M. Electrochemical Cycling-Induced Spinel Formation in High-Charge-Capacity Orthorhombic LiMnO2. J. Electrochem. Soc. 1999, 146, 3217– 3223,  DOI: 10.1149/1.1392457
    Google Scholar
    19
    Electrochemical cycling-induced spinel formation in high-charge-capacity orthorhombic LiMnO2
    Jang, Young-Il; Huang, Biying; Wang, Haifeng; Sadoway, Donald R.; Chiang, Yet-Ming
    Journal of the Electrochemical Society (1999), 146 (9), 3217-3223CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
    LixMn2O4 spinel normally undergoes a transformation from its cubic to tetragonal phase when x exceeds 1 due to a collective Jahn-Teller distortion, resulting in poor cyclability when both the 4 and 3 V intercalation plateaus are utilized. We show that this transformation is suppressed in spinels of compn. up to x ≈ 2 obtained through the electrochem. cycling of orthorhombic LiMnO2. X-ray diffraction, transmission electron microscopy, and high-resoln. electron microscopy studies together show that cycling produces a cubic spinel contg. partial tetrahedral cation site occupancy and a nanodomain structure (20 to 50 nm size) within parent single-cryst. oxide particles. This structure is responsible for the cycling stability of electrochem. produced spinel. The reversible capacity (272 mAh/g) and energy d. (853 Wh/kg) achieved at a low charge-discharge rate (3.33 mA/g) in the present samples are the highest among cryst. LiMnO2 materials reported to date.
  20. 20
    Paterson, A. J.; Armstrong, A. R.; Bruce, P. G. Stoichiometric LiMnO[sub 2] with a Layered Structure. J. Electrochem. Soc. 2004, 151, A1552– A1558,  DOI: 10.1149/1.1786074
    Google Scholar
    There is no corresponding record for this reference.
  21. 21
    Sato, T.; Sato, K.; Zhao, W.; Kajiya, Y.; Yabuuchi, N. Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2. J. Mater. Chem. A 2018, 6, 13943– 13951,  DOI: 10.1039/C8TA03667E
    Google Scholar
    21
    Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2
    Sato, Takahito; Sato, Kei; Zhao, Wenwen; Kajiya, Yoshio; Yabuuchi, Naoaki
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (28), 13943-13951CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Stoichiometric LiMnO2 and NaMnO2 with a cation-disordered rock salt-type structure as metastable polymorphs were successfully prepd. by mech. milling. Although cation-disordered rock salt phases with a stoichiometric compn. (Li:Mn molar ratio = 1:1) are expected to be electrochem. less active, both samples show superior performance as electrode materials when compared with thermodynamically stable layered phases in Li/Na cells. Both metastable samples deliver large reversible capacities, which correspond to >80% of their theor. capacities, with relatively small polarization on the basis of reversible Mn3+/Mn4+ redox. Moreover, for rock salt LiMnO2, the phase transition into a spinel phase is effectively suppressed compared with a thermodynamically stable phase. The electrode reversibility of NaMnO2 is also drastically improved by the use of the metastable phase with good capacity retention. Metastable phases with unique nanostructures open a new path for the design of advanced electrode materials with high energy d., and thus a broad impact is anticipated for rechargeable Li/Na battery applications.
  22. 22
    Tu, X. Y.; Shu, K. Y. X-ray diffraction study on phase transition of orthorhombic LiMnO2 in electrochemical conversions. J. Solid State Electrochem. 2008, 12, 245– 249,  DOI: 10.1007/s10008-007-0384-3
    Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Croguennec, L.; Deniard, P.; Brec, R.; Lecerf, A. Nature of the stacking faults in orthorhombic LiMnO2. J. Mater. Chem. 1997, 7, 511– 516,  DOI: 10.1039/a604947h
    Google Scholar
    23
    Nature of the stacking faults in orthorhombic LiMnO2
    Croguennec, Laurence; Deniard, Philippe; Brec, Raymond; Lecerf, Andre
    Journal of Materials Chemistry (1997), 7 (3), 511-516CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)
    The synthesis of orthorhombic LiMnO2 (O-LiMnO2) with very small crystals (diam. ≈ 0.3 μm) leads to peculiar x-ray diffraction patterns. Some reflections (with k even) remain thin allowing for cell parameter refinements, showing that, compared to phases with bigger crystals, b and c remain unchanged, whereas an important increase of the a parameter is obsd. Other reflections (with k = 2n+1 and h ≠ 0) are widened substantially, while the remnant peaks (k = 2n+1 and h = 0) undergo a strong asymmetrization. These features were related successfully to faults corresponding to a b/2 translation of a basic unit constituting O-LiMnO2. A simulation made with the Diffax program allowed good reprodn. of the exptl. x-ray diffraction data, showing a statistic distribution of the faults, at least for the low fault concns. corresponding to the samples under study. The insertion of the fault corresponds to the insertion of a monoclinic cell between two blocks of orthorhombic symmetry. This cell (a ≈ 5.53, b ≈ 2.80, c ≈ 5.30 Å) corresponds to a newly obtained monoclinic LiMnO2 phase obtained through a topotactic deintercalation of α-NaMnO2. The fault percentage of the compds. studied goes from 1 to 6% and is well correlated to the substitution ratio between Li and Mn when the fault occurrence is treated as a cationic disorder (only in the case of small disorder for which the lines remain treatable with the Rietveld refinement program). The fault percentage can also be detd. easily from the cell parameter relation a = x0a0 + xmamsinγ, where a0 and am are the parameters of the orthorhombic and monoclinic cell of the pure phases and x0 and xm their relative fractions, a being the parameter of the faulted phase as refined from the fault-unaffected thin reflection peaks.
  24. 24
    Abakumov, A. M.; Tsirlin, A. A.; Bakaimi, I.; Van Tendeloo, G.; Lappas, A. Multiple Twinning As a Structure Directing Mechanism in Layered Rock-Salt-Type Oxides: NaMnO2 Polymorphism, Redox Potentials, and Magnetism. Chem. Mater. 2014, 26, 3306– 3315,  DOI: 10.1021/cm5011696
    Google Scholar
    24
    Multiple Twinning as a Structure Directing Mechanism in Layered Rock-Salt-Type Oxides: NaMnO2 Polymorphism, Redox Potentials, and Magnetism
    Abakumov, Artem M.; Tsirlin, Alexander A.; Bakaimi, Ioanna; Van Tendeloo, Gustaaf; Lappas, Alexandros
    Chemistry of Materials (2014), 26 (10), 3306-3315CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    New polymorphs of NaMnO2 were obsd. using TEM and synchrotron x-ray powder diffraction. Coherent twin planes confined to the (NaMnO2) layers, parallel to the (10‾1) crystallog. planes of the monoclinic layered rock-salt-type α-NaMnO2 (O3) structure, form quasi-periodic modulated sequences, with the known α- and β-NaMnO2 polymorphs as the two limiting cases. The energy difference between the polymorphic forms, estd. using a DFT-based structure relaxation, is on the scale of the typical thermal energies that results in a high degree of stacking disorder in these compds. The results unveil the remarkable effect of the twin planes on both the magnetic and electrochem. properties. The polymorphism drives the magnetic ground state from a quasi-1D spin system for the geometrically frustrated α-polymorph through a two-leg spin ladder for the intermediate stacking sequence toward a quasi-2D magnet for the β-polymorph. A substantial increase of the equil. potential for Na deintercalation upon increasing the concn. of the twin planes is calcd., providing a possibility to tune the electrochem. potential of the layered rock-salt ABO2 cathodes by engineering the materials with a controlled concn. of twins. Crystallog. data and at. coordinates are given.
  25. 25
    Treacy, M. M. J.; Newsam, J. M.; Deem, M. W. A General Recursion Method for Calculating Diffracted Intensities from Crystals Containing Planar Faults. Proc. R. Soc. Math. Phys. Sci. 1991, 433, 499– 520
    Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Wang, H.; Jang, Y. I.; Chiang, Y. M. Origin of Cycling Stability in Monoclinic- and Orthorhombic-Phase Lithium Manganese Oxide Cathodes. Electrochem. Solid-State Lett. 1999, 2, 490,  DOI: 10.1149/1.1390880
    Google Scholar
    26
    Origin of cycling stability in monoclinic- and orthorhombic-phase lithium manganese oxide cathodes
    Wang, Haifeng; Jang, Young-Il.; Chiang, Yet-Ming
    Electrochemical and Solid-State Letters (1999), 2 (10), 490-493CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
    High-resoln. electron microscopy of electrochem. cycled LiMnO2 and LiAlyMn1-yO2 shows that both the orthorhombic and monoclinic (layered) polymorphs form antiphase domain microstructures of 5-20 nm size upon transforming to cubic spinel. During the subsequent cubic-tetragonal transformation, the antiphase domains become ferroelastic domains that are able to accommodate the large Jahn-Teller induced strain. Electron diffraction patterns show that much cubic spinel is retained at high overall lithiation. A partially inverse structure with some Mn occupying 8a tetrahedral sites is likely. These features of the transformed spinels provide for improved capacity retention upon cycling compared to conventional LiMn3O4.
  27. 27
    Okubo, M.; Mizuno, Y.; Yamada, H.; Kim, J.; Hosono, E.; Zhou, H.; Kudo, T.; Honma, I. Fast Li-Ion Insertion into Nanosized LiMn2O4 without Domain Boundaries. ACS Nano 2010, 4, 741– 752,  DOI: 10.1021/nn9012065
    Google Scholar
    27
    Fast Li-Ion Insertion into Nanosized LiMn2O4 without Domain Boundaries
    Okubo, Masashi; Mizuno, Yoshifumi; Yamada, Hirotoshi; Kim, Jedeok; Hosono, Eiji; Zhou, Haoshen; Kudo, Tetsuichi; Honma, Itaru
    ACS Nano (2010), 4 (2), 741-752CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    The effect of crystallite size on Li-ion insertion in electrode materials is of interest because of the need for nanoelectrodes in higher-power Li-ion rechargeable batteries. The effect of size on the electrochem. properties of LiMn2O4 was studied. Accurate size control of nanocryst. LiMn2O4, prepd. by a hydrothermal method, alters the phase diagram and the Li-ion insertion voltage. Nanocryst. LiMn2O4 with small crystals of 15 nm cannot accommodate domain boundaries between Li-rich and Li-poor phases due to interface energy, and therefore lithiation proceeds via solid soln. state without domain boundaries, enabling fast Li-ion insertion during the discharge process.
  28. 28
    Choi, J. U.; Voronina, N.; Sun, Y.-K.; Myung, S.-T. Recent Progress and Perspective of Advanced High-Energy Co-Less Ni-Rich Cathodes for Li-Ion Batteries: Yesterday, Today, and Tomorrow. Adv. Energy Mater. 2020, 10, 2002027,  DOI: 10.1002/aenm.202002027
    Google Scholar
    28
    Recent Progress and Perspective of Advanced High-Energy Co-Less Ni-Rich Cathodes for Li-Ion Batteries: Yesterday, Today, and Tomorrow
    Choi, Ji Ung; Voronina, Natalia; Sun, Yang-Kook; Myung, Seung-Taek
    Advanced Energy Materials (2020), 10 (42), 2002027CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell)
    A review. With the ever-increasing requirement for high-energy d. lithium-ion batteries (LIBs) to drive pure/hybrid elec. vehicles (EVs), considerable attention has been paid to the development of cathode materials with high energy densities because they ultimately det. the energy d. of LIBs. Notably, the cost of cathode materials is still the main obstacle hindering the extensive application of EVs, with the cost accounting for 40% of the total cost of fabricating LIBs. Therefore, enhancing the energy d. and simultaneously decreasing the cost of LIBs are essential for the success of EV/hybrid EV industries. Among the existing com. cathodes, Ni-rich layered cathodes are widely employed because of their high energy d., relatively good rate capability, and reasonable cycling performance. Ni-rich layered cathodes contg. Co are now being reconsidered due to the increasing price of Co, which is much higher than that of Ni and Mn. In this report, the recent developments and strategies in the improvement of the stabilities of the bulk and surface for Co-less Ni-rich layered cathode materials are reviewed.
  29. 29
    Jang, Y. I.; Huang, B.; Chiang, Y. M.; Sadoway, D. R. Stabilization of LiMnO2 in the α - NaFeO2 Structure Type by LiAlO2 Addition. Electrochem. Solid-State Lett. 1999, 1, 13– 16,  DOI: 10.1149/1.1390619
    Google Scholar
    There is no corresponding record for this reference.
  30. 30
    Ohzuku, T.; Kitagawa, M.; Hirai, T. Electrochemistry of Manganese-Dioxide in Lithium Nonaqueous Cell. 3. X-Ray Diffractional Study on the Reduction of Spinel-Related Manganese-Dioxide. J. Electrochem. Soc. 1990, 137, 769– 775,  DOI: 10.1149/1.2086552
    Google Scholar
    30
    Electrochemistry of manganese dioxide in lithium nonaqueous cell. III. X-ray diffractional study on the reduction of spinel-related manganese dioxide
    Ohzuku, Tsutomu; Kitagawa, Masaki; Hirai, Taketsugu
    Journal of the Electrochemical Society (1990), 137 (3), 769-75CODEN: JESOAN; ISSN:0013-4651.
    X-ray diffraction and electrochem. studies of the redn. of a spinel-related manganese dioxide, Li0.27(2)Mn2O4:MnO1.93 were carried out in Li nonaq. cells. The redn. of this oxide proceeded topotactically in 3 steps; a redn. in 2 phases [cubic: ac = 8.045(6) Å and ac = 8.142(2)Å] was characterized by a const. open-circuit voltage (OCV) of 4.110(5)V for 0.27(2) < x <0.60(3) in LixMn2O4, a redn. in 1 phase [cubic: ac = 8.142(2) - 8.239(3)Å] characterized by an S-shaped OCV curve [mid-point, 3.94(1)V] for 0.60(3) < x < 1.0, and a redn. in 2 phases of cubic [ac = 8.239(3)Å] and tetragonal [aT = 5.649(2)Å and cT = 9.253(5)Å] characterized by an L-shaped OCV curve at 2.957(5)V for 1.0 < x < 2.0. An obsd. voltage sepn. of ∼1 V, which begins at a crit. compn. of Li1.0Mn2O4, was considered from the structural data of LixMn2O4 to be a difference in a solid-state redox reaction of a MnO6-octahedron, i.e., the MnO68-(Oh)/MnO69-(Oh) vs. MnO68-(Oh)/MnO69-(D4h) redox reactions, and an effect of deformation of a MnO69--octahedron from Oh-symmetry to D4h-symmetry (Jahn-Teller distortion) upon an electrode potential of LixMn2O4 is discussed.
  31. 31
    Kubobuchi, K.; Mogi, M.; Matsumoto, M.; Baba, T.; Yogi, C.; Sato, C.; Yamamoto, T.; Mizoguchi, T.; Imai, H. A valence state evaluation of a positive electrode material in an Li-ion battery with first-principles K- and L-edge XANES spectral simulations and resonance photoelectron spectroscopy. J. Appl. Phys. 2016, 120, 142125,  DOI: 10.1063/1.4963379
    Google Scholar
    31
    A valence state evaluation of a positive electrode material in an Li-ion battery with first-principles K- and L-edge XANES spectral simulations and resonance photoelectron spectroscopy
    Kubobuchi, Kei; Mogi, Masato; Matsumoto, Masashi; Baba, Teruhisa; Yogi, Chihiro; Sato, Chikai; Yamamoto, Tomoyuki; Mizoguchi, Teruyasu; Imai, Hideto
    Journal of Applied Physics (Melville, NY, United States) (2016), 120 (14), 142125/1-142125/13CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    X-ray absorption near edge structure (XANES) anal. is an element-specific method for proving electronic state mostly in the field of applied physics, such as battery and catalysis reactions, where the valence change plays an important role. In particular, many results have been reported for the anal. of pos. electrode materials of Li-ion batteries, where multiple transition materials contribute to the reactions. However, XANES anal. has been limited to identifying the valence state simply in comparison with ref. materials. When the shape of XANES spectra shows complicated changes, we were not able to identify the valence states or est. the valence quant., resulting in insufficient reaction anal. To overcome such issues, we propose a valence state evaluation method using K- and L-edge XANES anal. with first-principles simulations. By using this method, we demonstrated that the complicated reaction mechanism of Li(Ni1/3Co1/3Mn1/3)O2 can be successfully analyzed for distinguishing each contribution of Ni, Co, Mn, and O to the redox reactions during charge operation. In addn. to the XANES anal., we applied resonant photoelectron spectroscopy (RPES) and diffraction anomalous fine structure spectroscopy (DAFS) with first-principles calcns. to the reaction anal. of Co and Mn, which shows no or very little contribution to the redox. The combination of RPES and first-principles calcns. successfully enables us to confirm the contribution of Co at high potential regions by electively observing Co 3d orbitals. Through the DAFS anal., we deeply analyzed the spectral features of Mn K-edges and concluded that the obsd. spectral shape change for Mn does not originate from the valence change but from the change in distribution of wave functions around Mn upon Li extn. (c) 2016 American Institute of Physics.
  32. 32
    Yabuuchi, N.; Kubota, K.; Aoki, Y.; Komaba, S. Understanding Particle-Size-Dependent Electrochemical Properties of Li2MnO3-Based Positive Electrode Materials for Rechargeable Lithium Batteries. J. Phys. Chem. C 2016, 120, 875– 885,  DOI: 10.1021/acs.jpcc.5b10517
    Google Scholar
    32
    Understanding Particle-Size-Dependent Electrochemical Properties of Li2MnO3-Based Positive Electrode Materials for Rechargeable Lithium Batteries
    Yabuuchi, Naoaki; Kubota, Kei; Aoki, Yoshinori; Komaba, Shinichi
    Journal of Physical Chemistry C (2016), 120 (2), 875-885CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Electrochem. properties of Li-excess electrode materials, Li1.2Co0.13Ni0.13Mn0.54O2, with different primary particle sizes are studied in Li cells, and phase transition behavior on continuous electrochem. cycles is systematically examd. Although the nanosize (<100 nm) sample delivers a large reversible capacity of 300 mAh g-1 at the initial cycle, capacity retention is not sufficient as a pos. electrode material. Moreover, unfavorable phase transition, gradual enrichment of trivalent manganese ions, and lowering structural symmetry is not avoidable on electrochem. cycles for a nanosize sample, which is confirmed by combined techniques of synchrotron X-ray diffraction, X-ray absorption spectroscopy, and XPS. A submicron-size sample also delivers a large reversible capacity of 250 mAh g-1 even though a slow activation process is obsd. accompanied with partial oxygen loss and migration oxide ions in the crystal lattice coupled with transition metal migration on the initial charge process. Such an unfavorable phase transition at room temp. is effectively suppressed by the use of a submicrosize sample with low surface area. However, suppression of the phase transition is found to be a kinetically controlled phenomena and is, therefore, unavoidable at elevated temps.
  33. 33
    Wang, H.; Jang, Y. I.; Chiang, Y. M. Origin of Cycling Stability in Monoclinic- and Orthorhombic-Phase Lithium Manganese Oxide Cathodes. Electrochem. Solid-State Lett. 1999, 2, 490– 493,  DOI: 10.1149/1.1390880
    Google Scholar
    33
    Origin of cycling stability in monoclinic- and orthorhombic-phase lithium manganese oxide cathodes
    Wang, Haifeng; Jang, Young-Il.; Chiang, Yet-Ming
    Electrochemical and Solid-State Letters (1999), 2 (10), 490-493CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
    High-resoln. electron microscopy of electrochem. cycled LiMnO2 and LiAlyMn1-yO2 shows that both the orthorhombic and monoclinic (layered) polymorphs form antiphase domain microstructures of 5-20 nm size upon transforming to cubic spinel. During the subsequent cubic-tetragonal transformation, the antiphase domains become ferroelastic domains that are able to accommodate the large Jahn-Teller induced strain. Electron diffraction patterns show that much cubic spinel is retained at high overall lithiation. A partially inverse structure with some Mn occupying 8a tetrahedral sites is likely. These features of the transformed spinels provide for improved capacity retention upon cycling compared to conventional LiMn3O4.
  34. 34
    Reed, J.; Ceder, G.; Van Der Ven, A. Layered-to-Spinel Phase Transition in Lix MnO2. Electrochem. Solid-State Lett. 2001, 4, A78,  DOI: 10.1149/1.1368896
    Google Scholar
    34
    Layered-to-spinel phase transition in LixMnO2
    Reed, J.; Ceder, G.; Van Der Ven, A.
    Electrochemical and Solid-State Letters (2001), 4 (6), A78-A81CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
    Ab initio calcns. suggest that partially lithiated layered LixMnO2 transforms to spinel in a two-stage process. In the first stage, a significant fraction of the Mn and Li ions rapidly occupy tetrahedral sites, forming a metastable intermediate. The second stage involves a more difficult coordinated rearrangement of Mn and Li ions to form spinel. This behavior is contrasted to LixCoO2. The susceptibility of Mn for migration into the Li layer is found to be controlled by oxidn. state, which suggests various means of inhibiting the transformation. These strategies could prove useful in the creation of superior Mn-based cathode materials.
  35. 35
    Uyama, T.; Mukai, K.; Yamada, I. High-pressure synthesis and electrochemical properties of tetragonal LiMnO2. RSC Adv. 2018, 8, 26325– 26334,  DOI: 10.1039/C8RA03722A
    Google Scholar
    35
    High-pressure synthesis and electrochemical properties of tetragonal LiMnO2
    Uyama, Takeshi; Mukai, Kazuhiko; Yamada, Ikuya
    RSC Advances (2018), 8 (46), 26325-26334CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    Tetragonal structured LiMnO2 (t-LiMnO2) samples were synthesized under pressures above 8 GPa and investigated as a pos. electrode material for lithium-ion batteries. Rietveld analyses based on X-ray diffraction measurements indicated that t-LiMnO2 belongs to a γ-LiFeO2-type crystal structure with the I41/amd space group. The charge capacity during the initial cycle was 37 mA h g-1 at 25 °C, but improved to 185 mA h g-1 at 40 °C with an av. voltage of 4.56 V vs. Li+/Li. This demonstrated the superiority of t-LiMnO2 over other lithium manganese oxides in terms of energy d. The X-ray diffraction measurements and Raman spectroscopy of cycled t-LiMnO2 indicated an irreversible transformation from the γ-LiFeO2-type structure into a LixMn2O4 spinel structure by the displacement of 25% of the Mn ions to vacant octahedral sites through adjacent octahedral sites.
  36. 36
    Unke, O. T.; Chmiela, S.; Sauceda, H. E.; Gastegger, M.; Poltavsky, I.; Schutt, K. T.; Tkatchenko, A.; Muller, K. R. Machine Learning Force Fields. Chem. Rev. 2021, 121, 10142– 10186,  DOI: 10.1021/acs.chemrev.0c01111
    Google Scholar
    36
    Machine Learning Force Fields
    Unke, Oliver T.; Chmiela, Stefan; Sauceda, Huziel E.; Gastegger, Michael; Poltavsky, Igor; Schuett, Kristof T.; Tkatchenko, Alexandre; Mueller, Klaus-Robert
    Chemical Reviews (Washington, DC, United States) (2021), 121 (16), 10142-10186CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. In recent years, the use of machine learning (ML) in computational chem. has enabled numerous advances previously out of reach due to the computational complexity of traditional electronic-structure methods. One of the most promising applications is the construction of ML-based force fields (FFs), with the aim to narrow the gap between the accuracy of ab initio methods and the efficiency of classical FFs. The key idea is to learn the statistical relation between chem. structure and potential energy without relying on a preconceived notion of fixed chem. bonds or knowledge about the relevant interactions. Such universal ML approxns. are in principle only limited by the quality and quantity of the ref. data used to train them. This review gives an overview of applications of ML-FFs and the chem. insights that can be obtained from them. The core concepts underlying ML-FFs are described in detail, and a step-by-step guide for constructing and testing them from scratch is given. The text concludes with a discussion of the challenges that remain to be overcome by the next generation of ML-FFs.
  37. 37
    Reed, J.; Ceder, G.; Van Der Ven, A. Layered-to-Spinel Phase Transition in LixMnO2. Electrochem. Solid-State Lett. 2001, 4, A78– A81,  DOI: 10.1149/1.1368896
    Google Scholar
    37
    Layered-to-spinel phase transition in LixMnO2
    Reed, J.; Ceder, G.; Van Der Ven, A.
    Electrochemical and Solid-State Letters (2001), 4 (6), A78-A81CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
    Ab initio calcns. suggest that partially lithiated layered LixMnO2 transforms to spinel in a two-stage process. In the first stage, a significant fraction of the Mn and Li ions rapidly occupy tetrahedral sites, forming a metastable intermediate. The second stage involves a more difficult coordinated rearrangement of Mn and Li ions to form spinel. This behavior is contrasted to LixCoO2. The susceptibility of Mn for migration into the Li layer is found to be controlled by oxidn. state, which suggests various means of inhibiting the transformation. These strategies could prove useful in the creation of superior Mn-based cathode materials.
  38. 38
    Reed, J.; Ceder, G. Role of Electronic Structure in the Susceptibility of Metastable Transition-Metal Oxide Structures to Transformation. Chem. Rev. 2004, 104, 4513– 4534,  DOI: 10.1021/cr020733x
    Google Scholar
    38
    Role of Electronic Structure in the Susceptibility of Metastable Transition-Metal Oxide Structures to Transformation
    Reed, John; Ceder, Gerbrand
    Chemical Reviews (Washington, DC, United States) (2004), 104 (10), 4513-4533CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review focused on the role electronic structure plays in detg. the site preference and mobility of 3d transition-metal ions in an oxide and how these factors in turn affect the resistance of metastable 3d transition-metal oxides against transformation. This is a relevant topic to the Li rechargeable battery field because 3d transition-metal oxides are often used as pos. electrode materials. Topics covered include: transformation mechanisms, d. functional theory, comparison between the activation barriers for Co and Mn migration, valence of Co and Mn during migration, ligand-Field effects on the energetics of migrating Co and Mn, important factors influencing Co and Mn site preference in ccp Oxides, effect of chem. substitutions on Mn site preference, qual. ionization scale, effect of valence on site preference of other 3d transition metals, and overall trends for 3d metals.
  39. 39
    Deng, B.; Zhong, P.; Jun, K.; Riebesell, J.; Han, K.; Bartel, C. J.; Ceder, G. CHGNet as a pretrained universal neural network potential for charge-informed atomistic modelling. Nature Machine Intelligence 2023, 5, 1031– 1041,  DOI: 10.1038/s42256-023-00716-3
    Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Konuma, I.; Ugata, Y.; Yabuuchi, N. A methodology to synthesize easily oxidized materials containing Li ions in an inert atmosphere. Energy Advances 2024, 3, 962– 967,  DOI: 10.1039/D4YA00089G
    Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Zhou, G.; Sun, X.; Li, Q.-H.; Wang, X.; Zhang, J.-N.; Yang, W.; Yu, X.; Xiao, R.; Li, H. Mn Ion Dissolution Mechanism for Lithium-Ion Battery with LiMn2O4 Cathode: In Situ Ultraviolet-Visible Spectroscopy and Ab Initio Molecular Dynamics Simulations. J. Phys. Chem. Lett. 2020, 11, 3051– 3057,  DOI: 10.1021/acs.jpclett.0c00936
    Google Scholar
    41
    Mn Ion Dissolution Mechanism for Lithium-Ion Battery with LiMn2O4 Cathode: In Situ Ultraviolet-Visible Spectroscopy and Ab Initio Molecular Dynamics Simulations
    Zhou, Ge; Sun, Xiaorui; Li, Qing-Hao; Wang, Xuelong; Zhang, Jie-Nan; Yang, Wanli; Yu, Xiqian; Xiao, Ruijuan; Li, Hong
    Journal of Physical Chemistry Letters (2020), 11 (8), 3051-3057CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The dissoln. of transition-metal (TM) cations into a liq. electrolyte from cathode material, such as Mn ion dissoln. from LiMn2O4 (LMO), is detrimental to the cycling performance of Li-ion batteries (LIBs). Though much attention has been paid to this issue, the behavior of Mn dissoln. has not been clearly revealed. In this work, by using a refined in situ UV-visible (UV-vis) spectroscopy technique, we monitored the concn. changes of dissolved Mn ions in liq. electrolyte from LMO at different state of charge (SOC), confirming the max. dissoln. concn. and rate at 4.3 V charged state and Mn2+ as the main species in the electrolyte. Through ab initio mol. dynamics (AIMD) simulations, we revealed that the Mn dissoln. process is highly related to surface structure evolution, solvent decompn., and lithium salt. These results will contribute to understanding TM dissoln. mechanisms at working conditions as well as the design of stable cathodes.
  42. 42
    Hofmann, M.; Nagler, F.; Kapuschinski, M.; Guntow, U.; Giffin, G. A. Surface Modification of LiNi0.8Co0.15Al0.05O2 Particles via Li3PO4 Coating to Enable Aqueous Electrode Processing. ChemSusChem 2020, 13, 5962– 5971,  DOI: 10.1002/cssc.202001907
    Google Scholar
    42
    Surface Modification of LiNi0.8Co0.15Al0.05O2 Particles via Li3PO4 Coating to Enable Aqueous Electrode Processing
    Hofmann, Michael; Nagler, Felix; Kapuschinski, Martina; Guntow, Uwe; Giffin, Guinevere A.
    ChemSusChem (2020), 13 (22), 5962-5971CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The successful implementation of an aq.-based electrode manufg. process for nickel-rich cathode active materials is challenging due to their high water sensitivity. In this work, the surface of LiNi0.8Co0.15Al0.05O2 (NCA) was modified with a lithium phosphate coating to investigate its ability to protect the active material during electrode prodn. The results illustrate that the coating amt. is crucial and a compromise has to be made between protection during electrode processing and sufficient electronic cond. through the particle surface. Cells with water-based electrodes contg. NCA with an optimized amt. of lithium phosphate had a slightly lower specific discharge capacity than cells with conventional N-methyl-2-pyrrolidone-based electrodes. Nonetheless, the cells with optimized water-based electrodes could compete in terms of cycle life.
  43. 43
    Komaba, S.; Itabashi, T.; Ohtsuka, T.; Groult, H.; Kumagai, N.; Kaplan, B.; Yashiro, H. Impact of 2-Vinylpyridine as Electrolyte Additive on Surface and Electrochemistry of Graphite for C/LiMn2O4 Li-Ion Cells. J. Electrochem. Soc. 2005, 152, A937,  DOI: 10.1149/1.1885385
    Google Scholar
    There is no corresponding record for this reference.
  44. 44
    Wang, J.; Yamada, Y.; Sodeyama, K.; Chiang, C. H.; Tateyama, Y.; Yamada, A. Superconcentrated electrolytes for a high-voltage lithium-ion battery. Nat. Commun. 2016, 7, 12032,  DOI: 10.1038/ncomms12032
    Google Scholar
    44
    Superconcentrated electrolytes for a high-voltage lithium-ion battery
    Wang, Jianhui; Yamada, Yuki; Sodeyama, Keitaro; Chiang, Ching Hua; Tateyama, Yoshitaka; Yamada, Atsuo
    Nature Communications (2016), 7 (), 12032CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    Finding a viable electrolyte for next-generation 5 V-class lithium-ion batteries is of primary importance. A long-standing obstacle has been metal-ion dissoln. at high voltages. The LiPF6 salt in conventional electrolytes is chem. unstable, which accelerates transition metal dissoln. of the electrode material, yet beneficially suppresses oxidative dissoln. of the aluminum current collector; replacing LiPF6 with more stable lithium salts may diminish transition metal dissoln. but unfortunately encounters severe aluminum oxidn. Here we report an electrolyte design that can solve this dilemma. By mixing a stable lithium salt LiN(SO2F)2 with di-Me carbonate solvent at extremely high concns., we obtain an unusual liq. showing a three-dimensional network of anions and solvent mols. that coordinate strongly to Li+ ions. This simple formulation of superconcd. LiN(SO2F)2/dimethyl carbonate electrolyte inhibits the dissoln. of both aluminum and transition metal at around 5 V, and realizes a high-voltage LiNi0.5Mn1.5O4/graphite battery that exhibits excellent cycling durability, high rate capability and enhanced safety.
  45. 45
    Paterson, A. J.; Armstrong, A. R.; Bruce, P. G. Stoichiometric LiMnO2 with a layered structure - Charge/discharge capacity and the influence of grinding. J. Electrochem. Soc. 2004, 151, A1552– A1558,  DOI: 10.1149/1.1786074
    Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Shimada, N.; Ugata, Y.; Nishikawa, S.; Shibata, D.; Ohta, T.; Yabuuchi, N. Improved electrode reversibility of anionic redox with highly concentrated electrolyte solution and aramid-coated polyolefin separator. Energy Advances 2023, 2, 508– 512,  DOI: 10.1039/D3YA00066D
    Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Ugata, Y.; Motoki, C.; Nishikawa, S.; Yabuuchi, N. Improved Reversibility of Lithium Deposition and Stripping with High Areal Capacity under Practical Conditions through Enhanced Wettability of Polyolefin Separator to Highly Concentrated Electrolyte. Energy Advances 2023, 2, 503– 507,  DOI: 10.1039/D2YA00359G
    Google Scholar
    There is no corresponding record for this reference.
  48. 48
    Ugata, Y.; Yabuuchi, N. New functionality of electrode materials with highly concentrated electrolytes. Trends in Chemistry 2023, 5, 672– 683,  DOI: 10.1016/j.trechm.2023.07.003
    Google Scholar
    There is no corresponding record for this reference.
  49. 49
    Izumi, F.; Momma, K. Three-Dimensional Visualization in Powder Diffraction. Solid State Phenom. 2007, 130, 15– 20,  DOI: 10.4028/www.scientific.net/SSP.130.15
    Google Scholar
    49
    Three-dimensional visualization in powder diffraction
    Izumi, Fujio; Momma, Koichi
    Diffusion and Defect Data--Solid State Data, Pt. B: Solid State Phenomena (2007), 130 (Applied Crystallography XX), 15-20CODEN: DDBPE8; ISSN:1012-0394. (Trans Tech Publications Ltd.)
    A multi-purpose pattern-fitting system, RIETAN-2000, has been extensively utilized to contribute to many structural studies. It offers a sophisticated structure-refinement technique of whole-pattern fitting based on the max.-entropy method (MEM) in combination with a MEM anal. program PRIMA. We have recently completed a successor system, RIETAN-FP, adding new features such as standardization of crystal-structure data, an extended March-Dollase preferred-orientation function, and automation of imposing restraints on bond lengths and angles. Further, we have been developing a new three-dimensional visualization system, VESTA, using wxWidgets as a C++ application framework. VESTA excels in visualization, rendering, and manipulation of crystal structures and electron/nuclear densities detd. by X-ray/neutron diffraction and electronic-structure calcns. VESTA also enables us to display wave functions and electrostatic potentials calcd. with part of these programs.
  50. 50
    Newville, M. IFEFFIT: interactive XAFS analysis and FEFF fitting. J. Synchrot. Radiat. 2001, 8, 322– 324,  DOI: 10.1107/S0909049500016964
    Google Scholar
    50
    IFEFFIT: interactive XAFS analysis and FEFF fitting
    Newville, Matthew
    Journal of Synchrotron Radiation (2001), 8 (2), 322-324CODEN: JSYRES; ISSN:0909-0495. (Munksgaard International Publishers Ltd.)
    IFEFFIT, an interactive program and scriptable library of XAFS algorithms is presented. The core algorithms of AUTOBK and FEFFIT were combined with general data manipulation and interactive graphics into a single package. IFEFFIT comes with a command-line program that can be run either interactively or in batch-mode. It also provides a library of functions that can be used easily from C or Fortran, as well as high level scripting languages such as Tcl, Perl and Python. Using this library, a Graphical User Interface for rapid 'online' data anal. is demonstrated. IFEFFIT is freely available with an Open Source license. Outside use, development, and contributions are encouraged.
  51. 51
    Wallwork, K. S.; Kennedy, B. J.; Wang, D. The High Resolution Powder Diffraction Beamline for the Australian Synchrotron. AIP Conf. Proc. 2007, 879, 879– 882
    Google Scholar
    51
    The high resolution powder diffraction beamline for the Australian Synchrotron
    Wallwork, Kia S.; Kennedy, Brendan J.; Wang, David
    AIP Conference Proceedings (2007), 879 (Pt. 1, Synchrotron Radiation Instrumentation, Part 1), 879-882CODEN: APCPCS; ISSN:0094-243X. (American Institute of Physics)
    A beamline for high resoln. powder diffraction studies will be installed as one of the first operational beamlines at the Australian Synchrotron and will be located on a bending magnet source. The beamline will be cable of using energies of 4-30 keV and comprise two end stations. The optical and end station design and performance specifications are presented.
  52. 52
    Ohara, K.; Tominaka, S.; Yamada, H.; Takahashi, M.; Yamaguchi, H.; Utsuno, F.; Umeki, T.; Yao, A.; Nakada, K.; Takemoto, M.; Hiroi, S.; Tsuji, N.; Wakihara, T. Time-resolved pair distribution function analysis of disordered materials on beamlines BL04B2 and BL08W at SPring-8. J. Synchrot. Radiat. 2018, 25, 1627– 1633,  DOI: 10.1107/S1600577518011232
    Google Scholar
    There is no corresponding record for this reference.
  53. 53
    Masese, T.; Miyazaki, Y.; Mbiti Kanyolo, G.; Takahashi, T.; Ito, M.; Senoh, H.; Saito, T. Topological Defects and Unique Stacking Disorders in Honeycomb Layered Oxide K2Ni2TeO6 Nanomaterials: Implications for Rechargeable Batteries. ACS Appl. Nano Mater. 2021, 4, 279– 287,  DOI: 10.1021/acsanm.0c02601
    Google Scholar
    53
    Topological Defects and Unique Stacking Disorders in Honeycomb Layered Oxide K2Ni2TeO6 Nanomaterials: Implications for Rechargeable Batteries
    Masese, Titus; Miyazaki, Yoshinobu; Mbiti Kanyolo, Godwill; Takahashi, Teruo; Ito, Miyu; Senoh, Hiroshi; Saito, Tomohiro
    ACS Applied Nano Materials (2021), 4 (1), 279-287CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
    Endowed with a multitude of exquisite properties such as rich electrochem., superb topol., and eccentric electromagnetic phenomena, honeycomb layered oxides have risen to the top echelons of science with applications in diverse fields ranging from condensed matter physics, solid-state chem., materials science, and solid-state ionics to electrochem. However, these oxides are vastly underutilized as their underlying atomistic mechanisms remain unexplored. Therefore, in this study, at.-resoln. imaging on pristine K2Ni2TeO6 along multiple zone axes was conducted using spherical aberration-cor. scanning transmission electron microscopy (Cs-cor. STEM) to reveal hitherto unreported nanoscale topol. defects and curvature which can be assocd. with various phase transitions. Furthermore, we discover the coexistence of a stacking variant with P3-type sequence alongside the well-reported P2-type stacking sequence in such honeycomb layered oxides. Our findings have the potential to inspire further exptl. and theor. studies into the role of stacking and topol. in the functionality of honeycomb layered oxides, for instance, as high-performance electrode materials for rechargeable batteries.
  54. 54
    Takamoto, S.; Shinagawa, C.; Motoki, D.; Nakago, K.; Li, W.; Kurata, I.; Watanabe, T.; Yayama, Y.; Iriguchi, H.; Asano, Y.; Onodera, T.; Ishii, T.; Kudo, T.; Ono, H.; Sawada, R.; Ishitani, R.; Ong, M.; Yamaguchi, T.; Kataoka, T.; Hayashi, A.; Charoenphakdee, N.; Ibuka, T. Towards universal neural network potential for material discovery applicable to arbitrary combination of 45 elements. Nat. Commun. 2022, 13, 2991,  DOI: 10.1038/s41467-022-30687-9
    Google Scholar
    54
    Towards universal neural network potential for material discovery applicable to arbitrary combination of 45 elements
    Takamoto, So; Shinagawa, Chikashi; Motoki, Daisuke; Nakago, Kosuke; Li, Wenwen; Kurata, Iori; Watanabe, Taku; Yayama, Yoshihiro; Iriguchi, Hiroki; Asano, Yusuke; Onodera, Tasuku; Ishii, Takafumi; Kudo, Takao; Ono, Hideki; Sawada, Ryohto; Ishitani, Ryuichiro; Ong, Marc; Yamaguchi, Taiki; Kataoka, Toshiki; Hayashi, Akihide; Charoenphakdee, Nontawat; Ibuka, Takeshi
    Nature Communications (2022), 13 (1), 2991CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
    Abstr.: Computational material discovery is under intense study owing to its ability to explore the vast space of chem. systems. Neural network potentials (NNPs) have been shown to be particularly effective in conducting atomistic simulations for such purposes. However, existing NNPs are generally designed for narrow target materials, making them unsuitable for broader applications in material discovery. Here we report a development of universal NNP called PreFerred Potential (PFP), which is able to handle any combination of 45 elements. Particular emphasis is placed on the datasets, which include a diverse set of virtual structures used to attain the universality. We demonstrated the applicability of PFP in selected domains: lithium diffusion in LiFeSO4F, mol. adsorption in metal-org. frameworks, an order-disorder transition of Cu-Au alloys, and material discovery for a Fischer-Tropsch catalyst. They showcase the power of PFP, and this technol. provides a highly useful tool for material discovery.
  55. 55
    Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
    Google Scholar
    55
    Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
    Kresse, G.; Furthmuller, J.
    Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
    The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
  56. 56
    Kresse, G.; Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 1996, 54, 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
    Google Scholar
    56
    Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
    Kresse, G.; Furthmueller, J.
    Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
  57. 57
    Anisimov, V. I.; Aryasetiawan, F.; Lichtenstein, A. I. First-principles calculations of the electronic structure and spectra of strongly correlated systems: theLDA+Umethod. J. Phys.: Condens. Matter 1997, 9, 767– 808,  DOI: 10.1088/0953-8984/9/4/002
    Google Scholar
    57
    First-principles calculations of the electronic structure and spectra of strongly correlated systems: the LDA + U method
    Anisimov, Vladimir I.; Aryasetiawan, F.; Lichtenstein, A. I.
    Journal of Physics: Condensed Matter (1997), 9 (4), 767-808CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
    A review with 75 refs. A generalization of the local-d. approxn. (LDA) method for systems with strong Coulomb correlations is described which gives a correct description of the Mott insulators. The LDA + U method (U = Coulomb interaction parameter) takes into account orbital dependence of the Coulomb and exchange interactions which is absent in the LDA. The scheme can be regarded as a "first-principles" method because there are no adjustable parameters. When applied to the transition metal compds. and rare earth metal compds., the LDA + U method gives a qual. improvement compared with the LDA not only for excited-state properties such as energy gaps but also for ground-state properties such as magnetic moments and interat. exchange parameters. The orbital-dependent rotationally invariant LDA + U potential gives a correct orbital polarization and a corresponding Jahn-Teller distortion as well as polaron formation.
  58. 58
    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
    Google Scholar
    58
    Generalized gradient approximation made simple
    Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
    Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
  59. 59
    Perdew, J. P.; Ruzsinszky, A.; Csonka, G. I.; Vydrov, O. A.; Scuseria, G. E.; Constantin, L. A.; Zhou, X.; Burke, K. Restoring the density-gradient expansion for exchange in solids and surfaces. Phys. Rev. Lett. 2008, 100, 136406,  DOI: 10.1103/PhysRevLett.100.136406
    Google Scholar
    59
    Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces
    Perdew, John P.; Ruzsinszky, Adrienn; Csonka, Gabor I.; Vydrov, Oleg A.; Scuseria, Gustavo E.; Constantin, Lucian A.; Zhou, Xiaolan; Burke, Kieron
    Physical Review Letters (2008), 100 (13), 136406/1-136406/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Popular modern generalized gradient approxns. are biased toward the description of free-atom energies. Restoration of the first-principles gradient expansion for exchange over a wide range of d. gradients eliminates this bias. We introduce a revised Perdew-Burke-Ernzerhof generalized gradient approxn. that improves equil. properties of densely packed solids and their surfaces.
  60. 60
    Jain, A.; Hautier, G.; Ong, S. P.; Moore, C. J.; Fischer, C. C.; Persson, K. A.; Ceder, G. Formation enthalpies by mixing GGA and GGA+Ucalculations. Phys. Rev. B 2011, 84, 045115,  DOI: 10.1103/PhysRevB.84.045115
    Google Scholar
    There is no corresponding record for this reference.
  61. 61
    Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 2011, 44, 1272– 1276,  DOI: 10.1107/S0021889811038970
    Google Scholar
    61
    VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data
    Momma, Koichi; Izumi, Fujio
    Journal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
    VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.

Cited By

Click to copy section linkSection link copied!
Citation Statements
Explore this article's citation statements on scite.ai
powered by  Scite

This article is cited by 9 publications.

  1. Suwon Lee, Seongkoo Kang, Youngju Choi, Jihyun Kim, Junghoon Yang, Daseul Han, Kyung-Wan Nam, Olaf J. Borkiewicz, Jiliang Zhang, Yong-Mook Kang. Structural Disorder of a Layered Lithium Manganese Oxide Cathode Paving a Reversible Phase Transition Route toward Its Theoretical Capacity. Journal of the American Chemical Society 2024, 146 (49) , 33845-33856. https://doi.org/10.1021/jacs.4c12248
  2. Muskan Srivastava, Anil Kumar M R, Sabbir Ahmed, Karim Zaghib. Exploring oxide cathodes for Li-ion batteries: From mineral mining to active material production. Journal of Power Sources 2025, 645 , 236968. https://doi.org/10.1016/j.jpowsour.2025.236968
  3. Yosuke Ugata, Chihaya Motoki, Tokuhiko Handa, Naoaki Yabuuchi. Practical assessment of cobalt-free Li2MnO3-based layered materials for Li battery applications. Solid State Ionics 2025, 424 , 116855. https://doi.org/10.1016/j.ssi.2025.116855
  4. Hakwoo Lee, Jihyun Kim, Suwon Lee, Maxim Avdeev, Wanli Yang, Yong‐Mook Kang. Characterizing Disorders Within Cathode Materials of Lithium‐Ion Batteries. Angewandte Chemie 2025, 135 https://doi.org/10.1002/ange.202501958
  5. Hakwoo Lee, Jihyun Kim, Suwon Lee, Maxim Avdeev, Wanli Yang, Yong‐Mook Kang. Characterizing Disorders Within Cathode Materials of Lithium‐Ion Batteries. Angewandte Chemie International Edition 2025, 135 https://doi.org/10.1002/anie.202501958
  6. Yun-Jae Song, Hyo-Jin Ahn. Controlling the Primary Particle of High-Nickel Cobalt-Free Cathodes for Highly Stable Lithium-Ion Batteries. Korean Journal of Chemical Engineering 2025, 45 https://doi.org/10.1007/s11814-025-00447-8
  7. Tucker Holstun, Tara P Mishra, Liliang Huang, Han‐Ming Hau, Shashwat Anand, Xiaochen Yang, Colin Ophus, Karen Bustillo, Lu ma, Steven Ehrlich, Gerbrand Ceder. Accelerating the Electrochemical Formation of the δ Phase in Manganese‐Rich Rocksalt Cathodes. Advanced Materials 2025, 37 (6) https://doi.org/10.1002/adma.202412871
  8. Susumu KUWABATA. Storage Batteries as a Key Device for Solving the Global Warming Issue—Team-based Research for Development of Rechargeable Batteries in the Green Technologies for Excellence (GteX) Program—. Electrochemistry 2025, https://doi.org/10.5796/electrochemistry.25-71066
  9. Yosuke Ugata, Tomohiro Kuriyama, Naoaki Yabuuchi. Efficient pathways to improve electrode performance of P′2 Na 2/3 MnO 2 for sodium batteries. Chemical Communications 2024, 61 (2) , 338-341. https://doi.org/10.1039/D4CC04719B
Download PDF
Go to ACS Central Science
Get e-Alerts
Get e-Alerts

ACS Central Science

Cite this: ACS Cent. Sci. 2024, 10, 9, 1718–1732
Click to copy citationCitation copied!
https://doi.org/10.1021/acscentsci.4c00578
Published August 26, 2024

Copyright © 2024 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Article Views

7794

Altmetric

-

Citations

9
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Synthesis of four different LiMnO2 polymorphs: (a) XRD patterns and schematic illustrations of crystal structures, (b) SEM images, (c) STEM images of heat-treated LiMnO2, (d) schematic illustration of domain structures for heat-treated LiMnO2, and (e) pair distribution functions of orthorhombic, heat-treated and monoclinic LiMnO2. Schematic illustrations of crystal structures were drawn using the VESTA program. (61)

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. Electrochemistry of different LiMnO2 polymorphs: Galvanostatic charge/discharge curves where (a) shows 1st–5th cycles and (b) 6th–10th cycles, (c) differential capacity plots, (d) changes in average discharge voltage, (e) capacity retention, (f) quasi-open circuit voltage for the 10th cycle, (g) energy density variations, and (h) discharge/charge rate capability of heat-treated LiMnO2.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. Structural characterization of different LiMnO2 polymorphs: (a) XRD patterns after 5 cycles. (b) Contour plot of operando XRD patterns, (c) X-ray absorption spectra, and (d) a high-resolution STEM image of heat-treated LiMnO2. The data of (d) was taken after 5 cycles. For (b), the 1st charge has a slight voltage drop around 150 min and to compensate and reach 4.8 V around 220 min the cell underwent the profile shown.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. Phase evolution on electrochemical cycles for different LiMnO2 polymorphs: (a) Schematic illustrations for phase transition processes and computational study for phase transition for delithiated phases (also see Supporting Figure S1c), with (b)–(d) showing the monoclinic-derived Li0.5MnO2, (e)–(f) the orthorhombic-derived Li0.5MnO2 and (g) comparison of stability with molecular dynamics simulations.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. Direct synthesis and electrode performance of “nanostructured LiMnO2”: (a) A scheme of the synthesis of nanostructured LiMnO2 and lithium phosphate coating. Synchrotron XRD data and STEM/EDX data of lithium phosphate coated LiMnO2. (b) Galvanostatic charge/discharge curves of nanostructured LiMnO2 at a rate of 10 mA g–1, (c) capacity and energy density retention of lithium phosphate coated LiMnO2 in conventional electrolyte and highly concentrated electrolyte solutions at a rate of 25 mA g–1, (d) Mn 2p XPS spectra of metallic Li electrodes after cycling in different electrolyte solutions, and (e) discharge/charge rate capability of lithium phosphate coated LiMnO2 in the conventional electrolyte solution.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 61 other publications.

    1. 1
      Ziegler, M. S.; Trancik, J. E. Re-examining rates of lithium-ion battery technology improvement and cost decline. Energy Environ. Sci. 2021, 14, 1635– 1651,  DOI: 10.1039/D0EE02681F
      There is no corresponding record for this reference.
    2. 2
      Olivetti, E. A.; Ceder, G.; Gaustad, G. G.; Fu, X. Lithium-Ion Battery Supply Chain Considerations: Analysis of Potential Bottlenecks in Critical Metals. Joule 2017, 1, 229– 243,  DOI: 10.1016/j.joule.2017.08.019
      There is no corresponding record for this reference.
    3. 3
      Vaalma, C.; Buchholz, D.; Weil, M.; Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat. Rev. Mater. 2018, 3, 18013,  DOI: 10.1038/natrevmats.2018.13
      There is no corresponding record for this reference.
    4. 4
      Aishova, A.; Park, G.-T.; Yoon, C. S.; Sun, Y.-K. Cobalt-Free High-Capacity Ni-Rich Layered Li[Ni0.9Mn0.1]O2 Cathode. Adv. Energy Mater. 2020, 10, 1903179,  DOI: 10.1002/aenm.201903179
      4
      Cobalt-Free High-Capacity Ni-Rich Layered Li[Ni0.9Mn0.1]O2 Cathode
      Aishova, Assylzat; Park, Geon-Tae; Yoon, Chong S.; Sun, Yang-Kook
      Advanced Energy Materials (2020), 10 (4), 1903179CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell)
      Li[Ni0.9Co0.1]O2 (NC90), Li[Ni0.9Co0.05Mn0.05]O2 (NCM90), and Li[Ni0.9Mn0.1]O2 (NM90) cathodes are synthesized for the development of a Co-free high-energy-d. cathode. NM90 maintains better cycling stability than the two Co-contg. cathodes, particularly under harsh cycling conditions (a discharge capacity of 236 mAh g-1 with a capacity retention of 88% when cycled at 4.4 V under 30°C and 93% retention when cycled at 4.3 V under 60°C after 100 cycles). The reason for the enhanced stability is mainly the ability of NM90 to absorb the strain assocd. with the abrupt anisotropic lattice contraction/extn. and to suppress the formation of microcracks, in addn. to enhanced chem. stability from the increased presence of stable Mn4+. Although the absence of Co deteriorates the rate capability, this can be overcome as the rate capability of the NM90 approaches that of the NCM90 when cycled at 60°C. The long-term cycling stability of NM90 is confirmed in a full cell, demonstrating that it is one of the most promising Co-free cathodes for high-energy-d. applications. This study not only provides insight into redefining the role of Mn in a Ni-rich cathode, it also represents a clear breakthrough in achieving a com. viable Co-free Ni-rich layered cathode.
    5. 5
      Geng, C.; Liu, A.; Dahn, J. R. Impact of Aluminum Added to Ni-Based Positive Electrode Materials by Dry Particle Fusion. Chem. Mater. 2020, 32, 6097– 6104,  DOI: 10.1021/acs.chemmater.0c01728
      5
      Impact of Aluminum Added to Ni-Based Positive Electrode Materials by Dry Particle Fusion
      Geng, Chenxi; Liu, Aaron; Dahn, Jeff R.
      Chemistry of Materials (2020), 32 (14), 6097-6104CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      This work reports two relatively new approaches to synthesize LiNi1-xAlxO2 materials. The first is coating Al2O3 on a Ni(OH)2 precursor by dry particle fusion followed by heating with LiOH·H2O. The second is coating Al2O3 on LiNiO2 by dry particle fusion followed by heating. X-ray diffraction (XRD), cross-sectional SEM (SEM), energy-dispersive spectroscopy (EDS) mapping, and EDS line scans were carried out. Coin-type cells were made to test the electrochem. performance of the synthesized materials. It was shown that Ni(OH)2 coated with 1, 2, and 3% Al2O3 followed by heating with LiOH·H2O had better capacity retention than samples prepd. by coating on LiNiO2 directly. Of all of the samples prepd., Ni(OH)2 coated with 3% Al2O3, followed by heating with LiOH·H2O had the largest specific discharge capacity and the best capacity retention. The reproducibility of this approach was verified by prepg. two more batches of Ni(OH)2 coated with 3% Al2O3 followed by heating with LiOH·H2O in the same way. This work suggests that coating desired materials on precursors by dry particle fusion is an attractive approach for synthesizing next-generation pos. electrode materials.
    6. 6
      Ikeda, N.; Konuma, I.; Rajendra, H. B.; Aida, T.; Yabuuchi, N. Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?. J. Mater. Chem. A 2021, 9, 15963– 15967,  DOI: 10.1039/D1TA03066C
      6
      Why is the O3 to O1 phase transition hindered in LiNiO2 on full delithiation?
      Ikeda, Naohiro; Konuma, Itsuki; Rajendra, Hongahally Basappa; Aida, Taira; Yabuuchi, Naoaki
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2021), 9 (29), 15963-15967CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Ni-enriched layered materials are utilized as pos. electrode materials of high-energy Li-ion batteries. Because electrode reversibility is gradually lost for stoichiometric LiNiO2 after continuous cycles, Ni ions are partially substituted by other metal ions (Co, Mn, Al etc.). However, the origin of deterioration in stoichiometric LiNiO2 is still not fully understand yet. Moreover, the loss of capacities is obsd. only in the high voltage region (>4.1 V), which is obviously different from the failure mode obsd. in other electrode materials. Here, we report for the first time the origin of deterioration, which is revealed by an in situ X-ray diffraction study. For fully charged NiO2, Ni ions migrate from original octahedral sites in NiO2 slabs to face-sharing tetrahedral sites in Li layers, by which the O3 to O1 phase transition is suppresed. Note that Ni migration is a reversible process, and the Ni ions migrate back to the original octahedral sites on discharge. However, after continuous cycles, the reversibility of Ni migration is gradually lost, and Ni ions are partially left at the tetrahedral sites in Li layers. Electrode kinetics are also deteriorated because of the Ni occupation in Li layers, and the accumulation of Ni ions at tetrahedral sites results in the loss of reversible capacities in the high voltage region. This finding opens a new way to design high-capacity Ni-enriched electrode materials, leading to the development of high-energy Li-ion batteries.
    7. 7
      Goonetilleke, D.; Riewald, F.; Kondrakov, A. O.; Janek, J.; Brezesinski, T.; Bianchini, M. Alleviating Anisotropic Volume Variation at Comparable Li Utilization during Cycling of Ni-Rich, Co-Free Layered Oxide Cathode Materials. J. Phys. Chem. C 2022, 126, 16952– 16964,  DOI: 10.1021/acs.jpcc.2c04946
      7
      Alleviating Anisotropic Volume Variation at Comparable Li Utilization during Cycling of Ni-Rich, Co-Free Layered Oxide Cathode Materials
      Goonetilleke, Damian; Riewald, Felix; Kondrakov, Aleksandr O.; Janek, Juergen; Brezesinski, Torsten; Bianchini, Matteo
      Journal of Physical Chemistry C (2022), 126 (40), 16952-16964CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Driven by demand for greater energy densities, Ni-rich cathode materials, such as lithium nickel cobalt manganese (NCM) and nickel cobalt aluminum (NCA) oxides, with compns. approaching the lithium nickel oxide (LiNiO2) end-member have been investigated intensively. While such compns. are targeted assuming the redox activity of nickel will lead to higher capacities, the role of even small amts. of Mn and Co in these systems is of great importance. To raise considerations about the role of Mn and Co, operando X-ray diffraction has been used to resolve the structure-electrochem. relationships in a series of Ni-rich NMX (LiNi1-yMnyO2, y = 0.25, 0.17, 0.10, 0.05) cathode materials. To ensure a meaningful comparison, the upper cutoff potential was varied as a function of the Mn content in the material to ensure comparable states of delithiation and thereby provide a capacity-normalized comparison of the structural evolution. During the first cycle all materials deliver a specific charge capacity exceeding 230 mAh g-1, corresponding to a residual Li content of x(Li) ≈ 0.15, and exhibit a structural evolution free of any first-order phase transitions. Monitoring the structural parameters of the materials during cycling shows that Mn substitution substantially reduces the magnitude of expansion/contraction of lattice parameters even when comparable amts. of Li are removed from the structure and more significantly also reduces the anisotropy of the vol. changes. Thus, these Co-free, Ni-rich materials hold promise as high-capacity cathodes with good structural and mech. stability.
    8. 8
      Konuma, I.; Ikeda, N.; Campéon, B. D. L.; Fujimura, H.; Kikkawa, J.; Luong, H. D.; Tateyama, Y.; Ugata, Y.; Yonemura, M.; Ishigaki, T.; Aida, T.; Yabuuchi, N. Unified understanding and mitigation of detrimental phase transition in cobalt-free LiNiO2. Energy Storage Mater. 2024, 66, 103200,  DOI: 10.1016/j.ensm.2024.103200
      There is no corresponding record for this reference.
    9. 9
      Mauler, L.; Lou, X.; Duffner, F.; Leker, J. Technological innovation vs. tightening raw material markets: falling battery costs put at risk. Energy Advances 2022, 1, 136– 145,  DOI: 10.1039/D1YA00052G
      There is no corresponding record for this reference.
    10. 10
      Hu, E.; Yu, X.; Lin, R.; Bi, X.; Lu, J.; Bak, S.; Nam, K.-W.; Xin, H. L.; Jaye, C.; Fischer, D. A.; Amine, K.; Yang, X.-Q. Evolution of redox couples in Li- and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release. Nat. Energy 2018, 3, 690– 698,  DOI: 10.1038/s41560-018-0207-z
      10
      Evolution of redox couples in Li- and Mn-rich cathode materials and mitigation of voltage fade by reducing oxygen release
      Hu, Enyuan; Yu, Xiqian; Lin, Ruoqian; Bi, Xuanxuan; Lu, Jun; Bak, Seongmin; Nam, Kyung-Wan; Xin, Huolin L.; Jaye, Cherno; Fischer, Daniel A.; Amine, Kahlil; Yang, Xiao-Qing
      Nature Energy (2018), 3 (8), 690-698CODEN: NEANFD; ISSN:2058-7546. (Nature Research)
      Voltage fade is a major problem in battery applications for high-energy lithium- and manganese-rich (LMR) layered materials. As a result of the complexity of the LMR structure, the voltage fade mechanism is not well understood. Here we conduct both in situ and ex situ studies on a typical LMR material (Li1.2Ni0.15Co0.1Mn0.55O2) during charge-discharge cycling, using multi-length-scale X-ray spectroscopic and three-dimensional electron microscopic imaging techniques. Through probing from the surface to the bulk, and from individual to whole ensembles of particles, we show that the av. valence state of each type of transition metal cation is continuously reduced, which is attributed to oxygen release from the LMR material. Such redns. activate the lower-voltage Mn3+/Mn4+ and Co2+/Co3+ redox couples in addn. to the original redox couples including Ni2+/Ni3+, Ni3+/Ni4+ and O2-/O-, directly leading to the voltage fade. We also show that the oxygen release causes microstructural defects such as the formation of large pores within particles, which also contributes to the voltage fade. Surface coating and modification methods are suggested to be effective in suppressing the voltage fade through reducing the oxygen release.
    11. 11
      Kobayashi, Y.; Sawamura, M.; Kondo, S.; Harada, M.; Noda, Y.; Nakayama, M.; Kobayakawa, S.; Zhao, W.; Nakao, A.; Yasui, A.; Rajendra, H. B.; Yamanaka, K.; Ohta, T.; Yabuuchi, N. Activation and stabilization mechanisms of anionic redox for Li storage applications: Joint experimental and theoretical study on Li2TiO3-LiMnO2 binary system. Mater. Today 2020, 37, 43– 55,  DOI: 10.1016/j.mattod.2020.03.002
      11
      Activation and stabilization mechanisms of anionic redox for Li storage applications: Joint experimental and theoretical study on Li2TiO3-LiMnO2 binary system
      Kobayashi, Yuki; Sawamura, Miho; Kondo, Sayaka; Harada, Maho; Noda, Yusuke; Nakayama, Masanobu; Kobayakawa, Sho; Zhao, Wenwen; Nakao, Aiko; Yasui, Akira; Rajendra, Hongahally Basappa; Yamanaka, Keisuke; Ohta, Toshiaki; Yabuuchi, Naoaki
      Materials Today (Oxford, United Kingdom) (2020), 37 (), 43-55CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)
      A binary system of Li2TiO3-LiMnO2 is systematically examd. by joint exptl. and theor. studies as electrode materials for Li storage applications. Increase in a fraction of Li2TiO3 effectively activates anionic redox, and thus holes are reversibly formed on oxygen by electrochem. oxidn. Such holes are energetically stabilized through π-type interaction with Mn t2g orbital as suggested by theor. calcn. However, excess enrichment of Li2TiO3 fractions in this binary system results in the oxygen loss as an irreversible process on delithiation because of a non-bonding character for Ti-O bonds coupled with the formation of O-O dimers, which are chem. and electrochem. unstable species. Detailed electrochem. study clearly shows that Li migration kinetics is relatively slow, presumably coupled with low electronic cond. Nevertheless, nanosizing of primary particles is an effective strategy to overcome this limitation. The nanosized sample prepd. by mech. milling delivers a large reversible capacity, ∼300 mA h g-1, even at room temp. and shows much improved capacity retention. Formation and stabilization of holes for the nanosized sample are also directly evidenced by soft X-ray absorption spectroscopy. From these results, factors affecting the reversibility of anionic redox as emerging new chem. and its possibility for energy storage applications are discussed in more details.
    12. 12
      Ji, H.; Wu, J.; Cai, Z.; Liu, J.; Kwon, D.-H.; Kim, H.; Urban, A.; Papp, J. K.; Foley, E.; Tian, Y.; Balasubramanian, M.; Kim, H.; Clément, R. J.; McCloskey, B. D.; Yang, W.; Ceder, G. Ultrahigh power and energy density in partially ordered lithium-ion cathode materials. Nat. Energy 2020, 5, 213– 221,  DOI: 10.1038/s41560-020-0573-1
      12
      Ultrahigh power and energy density in partially ordered lithium-ion cathode materials
      Ji, Huiwen; Wu, Jinpeng; Cai, Zijian; Liu, Jue; Kwon, Deok-Hwang; Kim, Hyunchul; Urban, Alexander; Papp, Joseph K.; Foley, Emily; Tian, Yaosen; Balasubramanian, Mahalingam; Kim, Haegyeom; Clement, Raphaele J.; McCloskey, Bryan D.; Yang, Wanli; Ceder, Gerbrand
      Nature Energy (2020), 5 (3), 213-221CODEN: NEANFD; ISSN:2058-7546. (Nature Research)
      The rapid market growth of rechargeable batteries requires electrode materials that combine high power and energy and are made from earth-abundant elements. Here we show that combining a partial spinel-like cation order and substantial lithium excess enables both dense and fast energy storage. Cation overstoichiometry and the resulting partial order is used to eliminate the phase transitions typical of ordered spinels and enable a larger practical capacity, while lithium excess is synergistically used with fluorine substitution to create a high lithium mobility. With this strategy, we achieved specific energies greater than 1,100 Wh kg-1 and discharge rates up to 20 A g-1. Remarkably, the cathode materials thus obtained from inexpensive manganese present a rare case wherein an excellent rate capability coexists with a reversible oxygen redox activity. Our work shows the potential for designing cathode materials in the vast space between fully ordered and disordered compds.
    13. 13
      Kanno, A.; Ugata, Y.; Ikeuchi, I.; Hibino, M.; Nakura, K.; Miyaoka, Y.; Kawamura, I.; Shibata, D.; Ohta, T.; Yabuuchi, N. Durable Manganese-Based Li-Excess Electrode Material without Voltage Decay: Metastable and Nanosized Li2MnO1.5F1.5. ACS Energy Lett. 2023, 8, 2753– 2761,  DOI: 10.1021/acsenergylett.3c00372
      There is no corresponding record for this reference.
    14. 14
      Reimers, J. N.; Fuller, E. W.; Rossen, E.; Dahn, J. R. Synthesis and Electrochemical Studies of LiMnO2 Prepared at Low Temperatures. J. Electrochem. Soc. 1993, 140, 3396– 3401,  DOI: 10.1149/1.2221101
      14
      Synthesis and electrochemical studies of LiMnO2 prepared at low temperatures
      Reimers, J. N.; Fuller, Eric W.; Rossen, Erik; Dahn, J. R.
      Journal of the Electrochemical Society (1993), 140 (12), 3396-401CODEN: JESOAN; ISSN:0013-4651.
      A new form of LiMnO2, which has recently been shown to reversibly intercalate lithium, has many advantages over other popular lithium-ion battery cathode materials. The authors describe improvements in the previously reported low temp. (300-450°) synthesis and report a new synthesis route based on ion exchange which takes place at 100°. Electrochem. performance is shown to be strongly dependent on synthesis temp. In situ x-ray diffraction and long time cycling measurements indicate that an irreversible structural transformation to disordered spinel takes place when Li is removed from LiMnO2. Nevertheless, the specific capacity of this material is over 190 mAh/g between 2.5 and 4.2 V.
    15. 15
      Armstrong, A. R.; Bruce, P. G. Synthesis of layered LiMnO2 as an electrode for rechargeable lithium batteries. Nature 1996, 381, 499– 500,  DOI: 10.1038/381499a0
      15
      Synthesis of layered LiMnO2 as an electrode for rechargeable lithium batteries
      Armstrong, A. Robert; Bruce, Peter G.
      Nature (London) (1996), 381 (6582), 499-500CODEN: NATUAS; ISSN:0028-0836. (Macmillan Magazines)
      We report the synthesis and electrochem. performance of a new material, layered LiMnO2, which is structurally analogous to LiCoO2 for rechargeable lithium batteries. The charge capacity of LiMnO2 (∼270 mA h g-1) compares well with that of both LiCoO2 and LiMn2O4, and preliminary results indicate good stability over repeated charge-discharge cycles.
    16. 16
      Capitaine, F.; Gravereau, P.; Delmas, C. A new variety of LiMnO2 with a layered structure. Solid State Ion. 1996, 89, 197– 202,  DOI: 10.1016/0167-2738(96)00369-4
      16
      A new variety of LiMnO2 with a layered structure
      Capitaine, F.; Gravereau, P.; Delmas, C.
      Solid State Ionics (1996), 89 (3,4), 197-202CODEN: SSIOD3; ISSN:0167-2738. (Elsevier)
      A new variety of LiMnO2 exhibiting a layered structure was obtained by chimie douce reaction from α-NaMnO2. This material crystallizes in the monoclinic system. Rietveld refinement of the x-ray diffraction pattern shows clearly that the MnO6 octahedra are strongly distorted, as the result of the Jahn-Teller effect on the trivalent Mn ions. Also, a small amt. of Mn is present within the Li layer, contrary to the α-NaMnO2 precursor phase which exhibits a strictly bidimensional structure. The thermal stability of LiMnO2 was studied by differential scanning calorimetry and by high temp. x-ray diffraction.
    17. 17
      Ohzuku, T.; Kitano, S.; Iwanaga, M.; Matsuno, H.; Ueda, A. Comparative study of Li[LixMn2 - xO4 and LT-LiMnO2 for lithium-ion batteries. J. Power Sources 1997, 68, 646– 651,  DOI: 10.1016/S0378-7753(96)02573-6
      There is no corresponding record for this reference.
    18. 18
      Ma, J.; Liu, T.; Ma, J.; Zhang, C.; Yang, J. Progress, Challenge, and Prospect of LiMnO2: An Adventure toward High-Energy and Low-Cost Li-Ion Batteries. Adv. Sci. 2024, 11, 2304938,  DOI: 10.1002/advs.202304938
      There is no corresponding record for this reference.
    19. 19
      Jang, Y. I.; Huang, B.; Wang, H.; Sadoway, D. R.; Chiang, Y. M. Electrochemical Cycling-Induced Spinel Formation in High-Charge-Capacity Orthorhombic LiMnO2. J. Electrochem. Soc. 1999, 146, 3217– 3223,  DOI: 10.1149/1.1392457
      19
      Electrochemical cycling-induced spinel formation in high-charge-capacity orthorhombic LiMnO2
      Jang, Young-Il; Huang, Biying; Wang, Haifeng; Sadoway, Donald R.; Chiang, Yet-Ming
      Journal of the Electrochemical Society (1999), 146 (9), 3217-3223CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)
      LixMn2O4 spinel normally undergoes a transformation from its cubic to tetragonal phase when x exceeds 1 due to a collective Jahn-Teller distortion, resulting in poor cyclability when both the 4 and 3 V intercalation plateaus are utilized. We show that this transformation is suppressed in spinels of compn. up to x ≈ 2 obtained through the electrochem. cycling of orthorhombic LiMnO2. X-ray diffraction, transmission electron microscopy, and high-resoln. electron microscopy studies together show that cycling produces a cubic spinel contg. partial tetrahedral cation site occupancy and a nanodomain structure (20 to 50 nm size) within parent single-cryst. oxide particles. This structure is responsible for the cycling stability of electrochem. produced spinel. The reversible capacity (272 mAh/g) and energy d. (853 Wh/kg) achieved at a low charge-discharge rate (3.33 mA/g) in the present samples are the highest among cryst. LiMnO2 materials reported to date.
    20. 20
      Paterson, A. J.; Armstrong, A. R.; Bruce, P. G. Stoichiometric LiMnO[sub 2] with a Layered Structure. J. Electrochem. Soc. 2004, 151, A1552– A1558,  DOI: 10.1149/1.1786074
      There is no corresponding record for this reference.
    21. 21
      Sato, T.; Sato, K.; Zhao, W.; Kajiya, Y.; Yabuuchi, N. Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2. J. Mater. Chem. A 2018, 6, 13943– 13951,  DOI: 10.1039/C8TA03667E
      21
      Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2
      Sato, Takahito; Sato, Kei; Zhao, Wenwen; Kajiya, Yoshio; Yabuuchi, Naoaki
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (28), 13943-13951CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Stoichiometric LiMnO2 and NaMnO2 with a cation-disordered rock salt-type structure as metastable polymorphs were successfully prepd. by mech. milling. Although cation-disordered rock salt phases with a stoichiometric compn. (Li:Mn molar ratio = 1:1) are expected to be electrochem. less active, both samples show superior performance as electrode materials when compared with thermodynamically stable layered phases in Li/Na cells. Both metastable samples deliver large reversible capacities, which correspond to >80% of their theor. capacities, with relatively small polarization on the basis of reversible Mn3+/Mn4+ redox. Moreover, for rock salt LiMnO2, the phase transition into a spinel phase is effectively suppressed compared with a thermodynamically stable phase. The electrode reversibility of NaMnO2 is also drastically improved by the use of the metastable phase with good capacity retention. Metastable phases with unique nanostructures open a new path for the design of advanced electrode materials with high energy d., and thus a broad impact is anticipated for rechargeable Li/Na battery applications.
    22. 22
      Tu, X. Y.; Shu, K. Y. X-ray diffraction study on phase transition of orthorhombic LiMnO2 in electrochemical conversions. J. Solid State Electrochem. 2008, 12, 245– 249,  DOI: 10.1007/s10008-007-0384-3
      There is no corresponding record for this reference.
    23. 23
      Croguennec, L.; Deniard, P.; Brec, R.; Lecerf, A. Nature of the stacking faults in orthorhombic LiMnO2. J. Mater. Chem. 1997, 7, 511– 516,  DOI: 10.1039/a604947h
      23
      Nature of the stacking faults in orthorhombic LiMnO2
      Croguennec, Laurence; Deniard, Philippe; Brec, Raymond; Lecerf, Andre
      Journal of Materials Chemistry (1997), 7 (3), 511-516CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)
      The synthesis of orthorhombic LiMnO2 (O-LiMnO2) with very small crystals (diam. ≈ 0.3 μm) leads to peculiar x-ray diffraction patterns. Some reflections (with k even) remain thin allowing for cell parameter refinements, showing that, compared to phases with bigger crystals, b and c remain unchanged, whereas an important increase of the a parameter is obsd. Other reflections (with k = 2n+1 and h ≠ 0) are widened substantially, while the remnant peaks (k = 2n+1 and h = 0) undergo a strong asymmetrization. These features were related successfully to faults corresponding to a b/2 translation of a basic unit constituting O-LiMnO2. A simulation made with the Diffax program allowed good reprodn. of the exptl. x-ray diffraction data, showing a statistic distribution of the faults, at least for the low fault concns. corresponding to the samples under study. The insertion of the fault corresponds to the insertion of a monoclinic cell between two blocks of orthorhombic symmetry. This cell (a ≈ 5.53, b ≈ 2.80, c ≈ 5.30 Å) corresponds to a newly obtained monoclinic LiMnO2 phase obtained through a topotactic deintercalation of α-NaMnO2. The fault percentage of the compds. studied goes from 1 to 6% and is well correlated to the substitution ratio between Li and Mn when the fault occurrence is treated as a cationic disorder (only in the case of small disorder for which the lines remain treatable with the Rietveld refinement program). The fault percentage can also be detd. easily from the cell parameter relation a = x0a0 + xmamsinγ, where a0 and am are the parameters of the orthorhombic and monoclinic cell of the pure phases and x0 and xm their relative fractions, a being the parameter of the faulted phase as refined from the fault-unaffected thin reflection peaks.
    24. 24
      Abakumov, A. M.; Tsirlin, A. A.; Bakaimi, I.; Van Tendeloo, G.; Lappas, A. Multiple Twinning As a Structure Directing Mechanism in Layered Rock-Salt-Type Oxides: NaMnO2 Polymorphism, Redox Potentials, and Magnetism. Chem. Mater. 2014, 26, 3306– 3315,  DOI: 10.1021/cm5011696
      24
      Multiple Twinning as a Structure Directing Mechanism in Layered Rock-Salt-Type Oxides: NaMnO2 Polymorphism, Redox Potentials, and Magnetism
      Abakumov, Artem M.; Tsirlin, Alexander A.; Bakaimi, Ioanna; Van Tendeloo, Gustaaf; Lappas, Alexandros
      Chemistry of Materials (2014), 26 (10), 3306-3315CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      New polymorphs of NaMnO2 were obsd. using TEM and synchrotron x-ray powder diffraction. Coherent twin planes confined to the (NaMnO2) layers, parallel to the (10‾1) crystallog. planes of the monoclinic layered rock-salt-type α-NaMnO2 (O3) structure, form quasi-periodic modulated sequences, with the known α- and β-NaMnO2 polymorphs as the two limiting cases. The energy difference between the polymorphic forms, estd. using a DFT-based structure relaxation, is on the scale of the typical thermal energies that results in a high degree of stacking disorder in these compds. The results unveil the remarkable effect of the twin planes on both the magnetic and electrochem. properties. The polymorphism drives the magnetic ground state from a quasi-1D spin system for the geometrically frustrated α-polymorph through a two-leg spin ladder for the intermediate stacking sequence toward a quasi-2D magnet for the β-polymorph. A substantial increase of the equil. potential for Na deintercalation upon increasing the concn. of the twin planes is calcd., providing a possibility to tune the electrochem. potential of the layered rock-salt ABO2 cathodes by engineering the materials with a controlled concn. of twins. Crystallog. data and at. coordinates are given.
    25. 25
      Treacy, M. M. J.; Newsam, J. M.; Deem, M. W. A General Recursion Method for Calculating Diffracted Intensities from Crystals Containing Planar Faults. Proc. R. Soc. Math. Phys. Sci. 1991, 433, 499– 520
      There is no corresponding record for this reference.
    26. 26
      Wang, H.; Jang, Y. I.; Chiang, Y. M. Origin of Cycling Stability in Monoclinic- and Orthorhombic-Phase Lithium Manganese Oxide Cathodes. Electrochem. Solid-State Lett. 1999, 2, 490,  DOI: 10.1149/1.1390880
      26
      Origin of cycling stability in monoclinic- and orthorhombic-phase lithium manganese oxide cathodes
      Wang, Haifeng; Jang, Young-Il.; Chiang, Yet-Ming
      Electrochemical and Solid-State Letters (1999), 2 (10), 490-493CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
      High-resoln. electron microscopy of electrochem. cycled LiMnO2 and LiAlyMn1-yO2 shows that both the orthorhombic and monoclinic (layered) polymorphs form antiphase domain microstructures of 5-20 nm size upon transforming to cubic spinel. During the subsequent cubic-tetragonal transformation, the antiphase domains become ferroelastic domains that are able to accommodate the large Jahn-Teller induced strain. Electron diffraction patterns show that much cubic spinel is retained at high overall lithiation. A partially inverse structure with some Mn occupying 8a tetrahedral sites is likely. These features of the transformed spinels provide for improved capacity retention upon cycling compared to conventional LiMn3O4.
    27. 27
      Okubo, M.; Mizuno, Y.; Yamada, H.; Kim, J.; Hosono, E.; Zhou, H.; Kudo, T.; Honma, I. Fast Li-Ion Insertion into Nanosized LiMn2O4 without Domain Boundaries. ACS Nano 2010, 4, 741– 752,  DOI: 10.1021/nn9012065
      27
      Fast Li-Ion Insertion into Nanosized LiMn2O4 without Domain Boundaries
      Okubo, Masashi; Mizuno, Yoshifumi; Yamada, Hirotoshi; Kim, Jedeok; Hosono, Eiji; Zhou, Haoshen; Kudo, Tetsuichi; Honma, Itaru
      ACS Nano (2010), 4 (2), 741-752CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      The effect of crystallite size on Li-ion insertion in electrode materials is of interest because of the need for nanoelectrodes in higher-power Li-ion rechargeable batteries. The effect of size on the electrochem. properties of LiMn2O4 was studied. Accurate size control of nanocryst. LiMn2O4, prepd. by a hydrothermal method, alters the phase diagram and the Li-ion insertion voltage. Nanocryst. LiMn2O4 with small crystals of 15 nm cannot accommodate domain boundaries between Li-rich and Li-poor phases due to interface energy, and therefore lithiation proceeds via solid soln. state without domain boundaries, enabling fast Li-ion insertion during the discharge process.
    28. 28
      Choi, J. U.; Voronina, N.; Sun, Y.-K.; Myung, S.-T. Recent Progress and Perspective of Advanced High-Energy Co-Less Ni-Rich Cathodes for Li-Ion Batteries: Yesterday, Today, and Tomorrow. Adv. Energy Mater. 2020, 10, 2002027,  DOI: 10.1002/aenm.202002027
      28
      Recent Progress and Perspective of Advanced High-Energy Co-Less Ni-Rich Cathodes for Li-Ion Batteries: Yesterday, Today, and Tomorrow
      Choi, Ji Ung; Voronina, Natalia; Sun, Yang-Kook; Myung, Seung-Taek
      Advanced Energy Materials (2020), 10 (42), 2002027CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell)
      A review. With the ever-increasing requirement for high-energy d. lithium-ion batteries (LIBs) to drive pure/hybrid elec. vehicles (EVs), considerable attention has been paid to the development of cathode materials with high energy densities because they ultimately det. the energy d. of LIBs. Notably, the cost of cathode materials is still the main obstacle hindering the extensive application of EVs, with the cost accounting for 40% of the total cost of fabricating LIBs. Therefore, enhancing the energy d. and simultaneously decreasing the cost of LIBs are essential for the success of EV/hybrid EV industries. Among the existing com. cathodes, Ni-rich layered cathodes are widely employed because of their high energy d., relatively good rate capability, and reasonable cycling performance. Ni-rich layered cathodes contg. Co are now being reconsidered due to the increasing price of Co, which is much higher than that of Ni and Mn. In this report, the recent developments and strategies in the improvement of the stabilities of the bulk and surface for Co-less Ni-rich layered cathode materials are reviewed.
    29. 29
      Jang, Y. I.; Huang, B.; Chiang, Y. M.; Sadoway, D. R. Stabilization of LiMnO2 in the α - NaFeO2 Structure Type by LiAlO2 Addition. Electrochem. Solid-State Lett. 1999, 1, 13– 16,  DOI: 10.1149/1.1390619
      There is no corresponding record for this reference.
    30. 30
      Ohzuku, T.; Kitagawa, M.; Hirai, T. Electrochemistry of Manganese-Dioxide in Lithium Nonaqueous Cell. 3. X-Ray Diffractional Study on the Reduction of Spinel-Related Manganese-Dioxide. J. Electrochem. Soc. 1990, 137, 769– 775,  DOI: 10.1149/1.2086552
      30
      Electrochemistry of manganese dioxide in lithium nonaqueous cell. III. X-ray diffractional study on the reduction of spinel-related manganese dioxide
      Ohzuku, Tsutomu; Kitagawa, Masaki; Hirai, Taketsugu
      Journal of the Electrochemical Society (1990), 137 (3), 769-75CODEN: JESOAN; ISSN:0013-4651.
      X-ray diffraction and electrochem. studies of the redn. of a spinel-related manganese dioxide, Li0.27(2)Mn2O4:MnO1.93 were carried out in Li nonaq. cells. The redn. of this oxide proceeded topotactically in 3 steps; a redn. in 2 phases [cubic: ac = 8.045(6) Å and ac = 8.142(2)Å] was characterized by a const. open-circuit voltage (OCV) of 4.110(5)V for 0.27(2) < x <0.60(3) in LixMn2O4, a redn. in 1 phase [cubic: ac = 8.142(2) - 8.239(3)Å] characterized by an S-shaped OCV curve [mid-point, 3.94(1)V] for 0.60(3) < x < 1.0, and a redn. in 2 phases of cubic [ac = 8.239(3)Å] and tetragonal [aT = 5.649(2)Å and cT = 9.253(5)Å] characterized by an L-shaped OCV curve at 2.957(5)V for 1.0 < x < 2.0. An obsd. voltage sepn. of ∼1 V, which begins at a crit. compn. of Li1.0Mn2O4, was considered from the structural data of LixMn2O4 to be a difference in a solid-state redox reaction of a MnO6-octahedron, i.e., the MnO68-(Oh)/MnO69-(Oh) vs. MnO68-(Oh)/MnO69-(D4h) redox reactions, and an effect of deformation of a MnO69--octahedron from Oh-symmetry to D4h-symmetry (Jahn-Teller distortion) upon an electrode potential of LixMn2O4 is discussed.
    31. 31
      Kubobuchi, K.; Mogi, M.; Matsumoto, M.; Baba, T.; Yogi, C.; Sato, C.; Yamamoto, T.; Mizoguchi, T.; Imai, H. A valence state evaluation of a positive electrode material in an Li-ion battery with first-principles K- and L-edge XANES spectral simulations and resonance photoelectron spectroscopy. J. Appl. Phys. 2016, 120, 142125,  DOI: 10.1063/1.4963379
      31
      A valence state evaluation of a positive electrode material in an Li-ion battery with first-principles K- and L-edge XANES spectral simulations and resonance photoelectron spectroscopy
      Kubobuchi, Kei; Mogi, Masato; Matsumoto, Masashi; Baba, Teruhisa; Yogi, Chihiro; Sato, Chikai; Yamamoto, Tomoyuki; Mizoguchi, Teruyasu; Imai, Hideto
      Journal of Applied Physics (Melville, NY, United States) (2016), 120 (14), 142125/1-142125/13CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      X-ray absorption near edge structure (XANES) anal. is an element-specific method for proving electronic state mostly in the field of applied physics, such as battery and catalysis reactions, where the valence change plays an important role. In particular, many results have been reported for the anal. of pos. electrode materials of Li-ion batteries, where multiple transition materials contribute to the reactions. However, XANES anal. has been limited to identifying the valence state simply in comparison with ref. materials. When the shape of XANES spectra shows complicated changes, we were not able to identify the valence states or est. the valence quant., resulting in insufficient reaction anal. To overcome such issues, we propose a valence state evaluation method using K- and L-edge XANES anal. with first-principles simulations. By using this method, we demonstrated that the complicated reaction mechanism of Li(Ni1/3Co1/3Mn1/3)O2 can be successfully analyzed for distinguishing each contribution of Ni, Co, Mn, and O to the redox reactions during charge operation. In addn. to the XANES anal., we applied resonant photoelectron spectroscopy (RPES) and diffraction anomalous fine structure spectroscopy (DAFS) with first-principles calcns. to the reaction anal. of Co and Mn, which shows no or very little contribution to the redox. The combination of RPES and first-principles calcns. successfully enables us to confirm the contribution of Co at high potential regions by electively observing Co 3d orbitals. Through the DAFS anal., we deeply analyzed the spectral features of Mn K-edges and concluded that the obsd. spectral shape change for Mn does not originate from the valence change but from the change in distribution of wave functions around Mn upon Li extn. (c) 2016 American Institute of Physics.
    32. 32
      Yabuuchi, N.; Kubota, K.; Aoki, Y.; Komaba, S. Understanding Particle-Size-Dependent Electrochemical Properties of Li2MnO3-Based Positive Electrode Materials for Rechargeable Lithium Batteries. J. Phys. Chem. C 2016, 120, 875– 885,  DOI: 10.1021/acs.jpcc.5b10517
      32
      Understanding Particle-Size-Dependent Electrochemical Properties of Li2MnO3-Based Positive Electrode Materials for Rechargeable Lithium Batteries
      Yabuuchi, Naoaki; Kubota, Kei; Aoki, Yoshinori; Komaba, Shinichi
      Journal of Physical Chemistry C (2016), 120 (2), 875-885CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Electrochem. properties of Li-excess electrode materials, Li1.2Co0.13Ni0.13Mn0.54O2, with different primary particle sizes are studied in Li cells, and phase transition behavior on continuous electrochem. cycles is systematically examd. Although the nanosize (<100 nm) sample delivers a large reversible capacity of 300 mAh g-1 at the initial cycle, capacity retention is not sufficient as a pos. electrode material. Moreover, unfavorable phase transition, gradual enrichment of trivalent manganese ions, and lowering structural symmetry is not avoidable on electrochem. cycles for a nanosize sample, which is confirmed by combined techniques of synchrotron X-ray diffraction, X-ray absorption spectroscopy, and XPS. A submicron-size sample also delivers a large reversible capacity of 250 mAh g-1 even though a slow activation process is obsd. accompanied with partial oxygen loss and migration oxide ions in the crystal lattice coupled with transition metal migration on the initial charge process. Such an unfavorable phase transition at room temp. is effectively suppressed by the use of a submicrosize sample with low surface area. However, suppression of the phase transition is found to be a kinetically controlled phenomena and is, therefore, unavoidable at elevated temps.
    33. 33
      Wang, H.; Jang, Y. I.; Chiang, Y. M. Origin of Cycling Stability in Monoclinic- and Orthorhombic-Phase Lithium Manganese Oxide Cathodes. Electrochem. Solid-State Lett. 1999, 2, 490– 493,  DOI: 10.1149/1.1390880
      33
      Origin of cycling stability in monoclinic- and orthorhombic-phase lithium manganese oxide cathodes
      Wang, Haifeng; Jang, Young-Il.; Chiang, Yet-Ming
      Electrochemical and Solid-State Letters (1999), 2 (10), 490-493CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
      High-resoln. electron microscopy of electrochem. cycled LiMnO2 and LiAlyMn1-yO2 shows that both the orthorhombic and monoclinic (layered) polymorphs form antiphase domain microstructures of 5-20 nm size upon transforming to cubic spinel. During the subsequent cubic-tetragonal transformation, the antiphase domains become ferroelastic domains that are able to accommodate the large Jahn-Teller induced strain. Electron diffraction patterns show that much cubic spinel is retained at high overall lithiation. A partially inverse structure with some Mn occupying 8a tetrahedral sites is likely. These features of the transformed spinels provide for improved capacity retention upon cycling compared to conventional LiMn3O4.
    34. 34
      Reed, J.; Ceder, G.; Van Der Ven, A. Layered-to-Spinel Phase Transition in Lix MnO2. Electrochem. Solid-State Lett. 2001, 4, A78,  DOI: 10.1149/1.1368896
      34
      Layered-to-spinel phase transition in LixMnO2
      Reed, J.; Ceder, G.; Van Der Ven, A.
      Electrochemical and Solid-State Letters (2001), 4 (6), A78-A81CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
      Ab initio calcns. suggest that partially lithiated layered LixMnO2 transforms to spinel in a two-stage process. In the first stage, a significant fraction of the Mn and Li ions rapidly occupy tetrahedral sites, forming a metastable intermediate. The second stage involves a more difficult coordinated rearrangement of Mn and Li ions to form spinel. This behavior is contrasted to LixCoO2. The susceptibility of Mn for migration into the Li layer is found to be controlled by oxidn. state, which suggests various means of inhibiting the transformation. These strategies could prove useful in the creation of superior Mn-based cathode materials.
    35. 35
      Uyama, T.; Mukai, K.; Yamada, I. High-pressure synthesis and electrochemical properties of tetragonal LiMnO2. RSC Adv. 2018, 8, 26325– 26334,  DOI: 10.1039/C8RA03722A
      35
      High-pressure synthesis and electrochemical properties of tetragonal LiMnO2
      Uyama, Takeshi; Mukai, Kazuhiko; Yamada, Ikuya
      RSC Advances (2018), 8 (46), 26325-26334CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Tetragonal structured LiMnO2 (t-LiMnO2) samples were synthesized under pressures above 8 GPa and investigated as a pos. electrode material for lithium-ion batteries. Rietveld analyses based on X-ray diffraction measurements indicated that t-LiMnO2 belongs to a γ-LiFeO2-type crystal structure with the I41/amd space group. The charge capacity during the initial cycle was 37 mA h g-1 at 25 °C, but improved to 185 mA h g-1 at 40 °C with an av. voltage of 4.56 V vs. Li+/Li. This demonstrated the superiority of t-LiMnO2 over other lithium manganese oxides in terms of energy d. The X-ray diffraction measurements and Raman spectroscopy of cycled t-LiMnO2 indicated an irreversible transformation from the γ-LiFeO2-type structure into a LixMn2O4 spinel structure by the displacement of 25% of the Mn ions to vacant octahedral sites through adjacent octahedral sites.
    36. 36
      Unke, O. T.; Chmiela, S.; Sauceda, H. E.; Gastegger, M.; Poltavsky, I.; Schutt, K. T.; Tkatchenko, A.; Muller, K. R. Machine Learning Force Fields. Chem. Rev. 2021, 121, 10142– 10186,  DOI: 10.1021/acs.chemrev.0c01111
      36
      Machine Learning Force Fields
      Unke, Oliver T.; Chmiela, Stefan; Sauceda, Huziel E.; Gastegger, Michael; Poltavsky, Igor; Schuett, Kristof T.; Tkatchenko, Alexandre; Mueller, Klaus-Robert
      Chemical Reviews (Washington, DC, United States) (2021), 121 (16), 10142-10186CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. In recent years, the use of machine learning (ML) in computational chem. has enabled numerous advances previously out of reach due to the computational complexity of traditional electronic-structure methods. One of the most promising applications is the construction of ML-based force fields (FFs), with the aim to narrow the gap between the accuracy of ab initio methods and the efficiency of classical FFs. The key idea is to learn the statistical relation between chem. structure and potential energy without relying on a preconceived notion of fixed chem. bonds or knowledge about the relevant interactions. Such universal ML approxns. are in principle only limited by the quality and quantity of the ref. data used to train them. This review gives an overview of applications of ML-FFs and the chem. insights that can be obtained from them. The core concepts underlying ML-FFs are described in detail, and a step-by-step guide for constructing and testing them from scratch is given. The text concludes with a discussion of the challenges that remain to be overcome by the next generation of ML-FFs.
    37. 37
      Reed, J.; Ceder, G.; Van Der Ven, A. Layered-to-Spinel Phase Transition in LixMnO2. Electrochem. Solid-State Lett. 2001, 4, A78– A81,  DOI: 10.1149/1.1368896
      37
      Layered-to-spinel phase transition in LixMnO2
      Reed, J.; Ceder, G.; Van Der Ven, A.
      Electrochemical and Solid-State Letters (2001), 4 (6), A78-A81CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)
      Ab initio calcns. suggest that partially lithiated layered LixMnO2 transforms to spinel in a two-stage process. In the first stage, a significant fraction of the Mn and Li ions rapidly occupy tetrahedral sites, forming a metastable intermediate. The second stage involves a more difficult coordinated rearrangement of Mn and Li ions to form spinel. This behavior is contrasted to LixCoO2. The susceptibility of Mn for migration into the Li layer is found to be controlled by oxidn. state, which suggests various means of inhibiting the transformation. These strategies could prove useful in the creation of superior Mn-based cathode materials.
    38. 38
      Reed, J.; Ceder, G. Role of Electronic Structure in the Susceptibility of Metastable Transition-Metal Oxide Structures to Transformation. Chem. Rev. 2004, 104, 4513– 4534,  DOI: 10.1021/cr020733x
      38
      Role of Electronic Structure in the Susceptibility of Metastable Transition-Metal Oxide Structures to Transformation
      Reed, John; Ceder, Gerbrand
      Chemical Reviews (Washington, DC, United States) (2004), 104 (10), 4513-4533CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review focused on the role electronic structure plays in detg. the site preference and mobility of 3d transition-metal ions in an oxide and how these factors in turn affect the resistance of metastable 3d transition-metal oxides against transformation. This is a relevant topic to the Li rechargeable battery field because 3d transition-metal oxides are often used as pos. electrode materials. Topics covered include: transformation mechanisms, d. functional theory, comparison between the activation barriers for Co and Mn migration, valence of Co and Mn during migration, ligand-Field effects on the energetics of migrating Co and Mn, important factors influencing Co and Mn site preference in ccp Oxides, effect of chem. substitutions on Mn site preference, qual. ionization scale, effect of valence on site preference of other 3d transition metals, and overall trends for 3d metals.
    39. 39
      Deng, B.; Zhong, P.; Jun, K.; Riebesell, J.; Han, K.; Bartel, C. J.; Ceder, G. CHGNet as a pretrained universal neural network potential for charge-informed atomistic modelling. Nature Machine Intelligence 2023, 5, 1031– 1041,  DOI: 10.1038/s42256-023-00716-3
      There is no corresponding record for this reference.
    40. 40
      Konuma, I.; Ugata, Y.; Yabuuchi, N. A methodology to synthesize easily oxidized materials containing Li ions in an inert atmosphere. Energy Advances 2024, 3, 962– 967,  DOI: 10.1039/D4YA00089G
      There is no corresponding record for this reference.
    41. 41
      Zhou, G.; Sun, X.; Li, Q.-H.; Wang, X.; Zhang, J.-N.; Yang, W.; Yu, X.; Xiao, R.; Li, H. Mn Ion Dissolution Mechanism for Lithium-Ion Battery with LiMn2O4 Cathode: In Situ Ultraviolet-Visible Spectroscopy and Ab Initio Molecular Dynamics Simulations. J. Phys. Chem. Lett. 2020, 11, 3051– 3057,  DOI: 10.1021/acs.jpclett.0c00936
      41
      Mn Ion Dissolution Mechanism for Lithium-Ion Battery with LiMn2O4 Cathode: In Situ Ultraviolet-Visible Spectroscopy and Ab Initio Molecular Dynamics Simulations
      Zhou, Ge; Sun, Xiaorui; Li, Qing-Hao; Wang, Xuelong; Zhang, Jie-Nan; Yang, Wanli; Yu, Xiqian; Xiao, Ruijuan; Li, Hong
      Journal of Physical Chemistry Letters (2020), 11 (8), 3051-3057CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The dissoln. of transition-metal (TM) cations into a liq. electrolyte from cathode material, such as Mn ion dissoln. from LiMn2O4 (LMO), is detrimental to the cycling performance of Li-ion batteries (LIBs). Though much attention has been paid to this issue, the behavior of Mn dissoln. has not been clearly revealed. In this work, by using a refined in situ UV-visible (UV-vis) spectroscopy technique, we monitored the concn. changes of dissolved Mn ions in liq. electrolyte from LMO at different state of charge (SOC), confirming the max. dissoln. concn. and rate at 4.3 V charged state and Mn2+ as the main species in the electrolyte. Through ab initio mol. dynamics (AIMD) simulations, we revealed that the Mn dissoln. process is highly related to surface structure evolution, solvent decompn., and lithium salt. These results will contribute to understanding TM dissoln. mechanisms at working conditions as well as the design of stable cathodes.
    42. 42
      Hofmann, M.; Nagler, F.; Kapuschinski, M.; Guntow, U.; Giffin, G. A. Surface Modification of LiNi0.8Co0.15Al0.05O2 Particles via Li3PO4 Coating to Enable Aqueous Electrode Processing. ChemSusChem 2020, 13, 5962– 5971,  DOI: 10.1002/cssc.202001907
      42
      Surface Modification of LiNi0.8Co0.15Al0.05O2 Particles via Li3PO4 Coating to Enable Aqueous Electrode Processing
      Hofmann, Michael; Nagler, Felix; Kapuschinski, Martina; Guntow, Uwe; Giffin, Guinevere A.
      ChemSusChem (2020), 13 (22), 5962-5971CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The successful implementation of an aq.-based electrode manufg. process for nickel-rich cathode active materials is challenging due to their high water sensitivity. In this work, the surface of LiNi0.8Co0.15Al0.05O2 (NCA) was modified with a lithium phosphate coating to investigate its ability to protect the active material during electrode prodn. The results illustrate that the coating amt. is crucial and a compromise has to be made between protection during electrode processing and sufficient electronic cond. through the particle surface. Cells with water-based electrodes contg. NCA with an optimized amt. of lithium phosphate had a slightly lower specific discharge capacity than cells with conventional N-methyl-2-pyrrolidone-based electrodes. Nonetheless, the cells with optimized water-based electrodes could compete in terms of cycle life.
    43. 43
      Komaba, S.; Itabashi, T.; Ohtsuka, T.; Groult, H.; Kumagai, N.; Kaplan, B.; Yashiro, H. Impact of 2-Vinylpyridine as Electrolyte Additive on Surface and Electrochemistry of Graphite for C/LiMn2O4 Li-Ion Cells. J. Electrochem. Soc. 2005, 152, A937,  DOI: 10.1149/1.1885385
      There is no corresponding record for this reference.
    44. 44
      Wang, J.; Yamada, Y.; Sodeyama, K.; Chiang, C. H.; Tateyama, Y.; Yamada, A. Superconcentrated electrolytes for a high-voltage lithium-ion battery. Nat. Commun. 2016, 7, 12032,  DOI: 10.1038/ncomms12032
      44
      Superconcentrated electrolytes for a high-voltage lithium-ion battery
      Wang, Jianhui; Yamada, Yuki; Sodeyama, Keitaro; Chiang, Ching Hua; Tateyama, Yoshitaka; Yamada, Atsuo
      Nature Communications (2016), 7 (), 12032CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Finding a viable electrolyte for next-generation 5 V-class lithium-ion batteries is of primary importance. A long-standing obstacle has been metal-ion dissoln. at high voltages. The LiPF6 salt in conventional electrolytes is chem. unstable, which accelerates transition metal dissoln. of the electrode material, yet beneficially suppresses oxidative dissoln. of the aluminum current collector; replacing LiPF6 with more stable lithium salts may diminish transition metal dissoln. but unfortunately encounters severe aluminum oxidn. Here we report an electrolyte design that can solve this dilemma. By mixing a stable lithium salt LiN(SO2F)2 with di-Me carbonate solvent at extremely high concns., we obtain an unusual liq. showing a three-dimensional network of anions and solvent mols. that coordinate strongly to Li+ ions. This simple formulation of superconcd. LiN(SO2F)2/dimethyl carbonate electrolyte inhibits the dissoln. of both aluminum and transition metal at around 5 V, and realizes a high-voltage LiNi0.5Mn1.5O4/graphite battery that exhibits excellent cycling durability, high rate capability and enhanced safety.
    45. 45
      Paterson, A. J.; Armstrong, A. R.; Bruce, P. G. Stoichiometric LiMnO2 with a layered structure - Charge/discharge capacity and the influence of grinding. J. Electrochem. Soc. 2004, 151, A1552– A1558,  DOI: 10.1149/1.1786074
      There is no corresponding record for this reference.
    46. 46
      Shimada, N.; Ugata, Y.; Nishikawa, S.; Shibata, D.; Ohta, T.; Yabuuchi, N. Improved electrode reversibility of anionic redox with highly concentrated electrolyte solution and aramid-coated polyolefin separator. Energy Advances 2023, 2, 508– 512,  DOI: 10.1039/D3YA00066D
      There is no corresponding record for this reference.
    47. 47
      Ugata, Y.; Motoki, C.; Nishikawa, S.; Yabuuchi, N. Improved Reversibility of Lithium Deposition and Stripping with High Areal Capacity under Practical Conditions through Enhanced Wettability of Polyolefin Separator to Highly Concentrated Electrolyte. Energy Advances 2023, 2, 503– 507,  DOI: 10.1039/D2YA00359G
      There is no corresponding record for this reference.
    48. 48
      Ugata, Y.; Yabuuchi, N. New functionality of electrode materials with highly concentrated electrolytes. Trends in Chemistry 2023, 5, 672– 683,  DOI: 10.1016/j.trechm.2023.07.003
      There is no corresponding record for this reference.
    49. 49
      Izumi, F.; Momma, K. Three-Dimensional Visualization in Powder Diffraction. Solid State Phenom. 2007, 130, 15– 20,  DOI: 10.4028/www.scientific.net/SSP.130.15
      49
      Three-dimensional visualization in powder diffraction
      Izumi, Fujio; Momma, Koichi
      Diffusion and Defect Data--Solid State Data, Pt. B: Solid State Phenomena (2007), 130 (Applied Crystallography XX), 15-20CODEN: DDBPE8; ISSN:1012-0394. (Trans Tech Publications Ltd.)
      A multi-purpose pattern-fitting system, RIETAN-2000, has been extensively utilized to contribute to many structural studies. It offers a sophisticated structure-refinement technique of whole-pattern fitting based on the max.-entropy method (MEM) in combination with a MEM anal. program PRIMA. We have recently completed a successor system, RIETAN-FP, adding new features such as standardization of crystal-structure data, an extended March-Dollase preferred-orientation function, and automation of imposing restraints on bond lengths and angles. Further, we have been developing a new three-dimensional visualization system, VESTA, using wxWidgets as a C++ application framework. VESTA excels in visualization, rendering, and manipulation of crystal structures and electron/nuclear densities detd. by X-ray/neutron diffraction and electronic-structure calcns. VESTA also enables us to display wave functions and electrostatic potentials calcd. with part of these programs.
    50. 50
      Newville, M. IFEFFIT: interactive XAFS analysis and FEFF fitting. J. Synchrot. Radiat. 2001, 8, 322– 324,  DOI: 10.1107/S0909049500016964
      50
      IFEFFIT: interactive XAFS analysis and FEFF fitting
      Newville, Matthew
      Journal of Synchrotron Radiation (2001), 8 (2), 322-324CODEN: JSYRES; ISSN:0909-0495. (Munksgaard International Publishers Ltd.)
      IFEFFIT, an interactive program and scriptable library of XAFS algorithms is presented. The core algorithms of AUTOBK and FEFFIT were combined with general data manipulation and interactive graphics into a single package. IFEFFIT comes with a command-line program that can be run either interactively or in batch-mode. It also provides a library of functions that can be used easily from C or Fortran, as well as high level scripting languages such as Tcl, Perl and Python. Using this library, a Graphical User Interface for rapid 'online' data anal. is demonstrated. IFEFFIT is freely available with an Open Source license. Outside use, development, and contributions are encouraged.
    51. 51
      Wallwork, K. S.; Kennedy, B. J.; Wang, D. The High Resolution Powder Diffraction Beamline for the Australian Synchrotron. AIP Conf. Proc. 2007, 879, 879– 882
      51
      The high resolution powder diffraction beamline for the Australian Synchrotron
      Wallwork, Kia S.; Kennedy, Brendan J.; Wang, David
      AIP Conference Proceedings (2007), 879 (Pt. 1, Synchrotron Radiation Instrumentation, Part 1), 879-882CODEN: APCPCS; ISSN:0094-243X. (American Institute of Physics)
      A beamline for high resoln. powder diffraction studies will be installed as one of the first operational beamlines at the Australian Synchrotron and will be located on a bending magnet source. The beamline will be cable of using energies of 4-30 keV and comprise two end stations. The optical and end station design and performance specifications are presented.
    52. 52
      Ohara, K.; Tominaka, S.; Yamada, H.; Takahashi, M.; Yamaguchi, H.; Utsuno, F.; Umeki, T.; Yao, A.; Nakada, K.; Takemoto, M.; Hiroi, S.; Tsuji, N.; Wakihara, T. Time-resolved pair distribution function analysis of disordered materials on beamlines BL04B2 and BL08W at SPring-8. J. Synchrot. Radiat. 2018, 25, 1627– 1633,  DOI: 10.1107/S1600577518011232
      There is no corresponding record for this reference.
    53. 53
      Masese, T.; Miyazaki, Y.; Mbiti Kanyolo, G.; Takahashi, T.; Ito, M.; Senoh, H.; Saito, T. Topological Defects and Unique Stacking Disorders in Honeycomb Layered Oxide K2Ni2TeO6 Nanomaterials: Implications for Rechargeable Batteries. ACS Appl. Nano Mater. 2021, 4, 279– 287,  DOI: 10.1021/acsanm.0c02601
      53
      Topological Defects and Unique Stacking Disorders in Honeycomb Layered Oxide K2Ni2TeO6 Nanomaterials: Implications for Rechargeable Batteries
      Masese, Titus; Miyazaki, Yoshinobu; Mbiti Kanyolo, Godwill; Takahashi, Teruo; Ito, Miyu; Senoh, Hiroshi; Saito, Tomohiro
      ACS Applied Nano Materials (2021), 4 (1), 279-287CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
      Endowed with a multitude of exquisite properties such as rich electrochem., superb topol., and eccentric electromagnetic phenomena, honeycomb layered oxides have risen to the top echelons of science with applications in diverse fields ranging from condensed matter physics, solid-state chem., materials science, and solid-state ionics to electrochem. However, these oxides are vastly underutilized as their underlying atomistic mechanisms remain unexplored. Therefore, in this study, at.-resoln. imaging on pristine K2Ni2TeO6 along multiple zone axes was conducted using spherical aberration-cor. scanning transmission electron microscopy (Cs-cor. STEM) to reveal hitherto unreported nanoscale topol. defects and curvature which can be assocd. with various phase transitions. Furthermore, we discover the coexistence of a stacking variant with P3-type sequence alongside the well-reported P2-type stacking sequence in such honeycomb layered oxides. Our findings have the potential to inspire further exptl. and theor. studies into the role of stacking and topol. in the functionality of honeycomb layered oxides, for instance, as high-performance electrode materials for rechargeable batteries.
    54. 54
      Takamoto, S.; Shinagawa, C.; Motoki, D.; Nakago, K.; Li, W.; Kurata, I.; Watanabe, T.; Yayama, Y.; Iriguchi, H.; Asano, Y.; Onodera, T.; Ishii, T.; Kudo, T.; Ono, H.; Sawada, R.; Ishitani, R.; Ong, M.; Yamaguchi, T.; Kataoka, T.; Hayashi, A.; Charoenphakdee, N.; Ibuka, T. Towards universal neural network potential for material discovery applicable to arbitrary combination of 45 elements. Nat. Commun. 2022, 13, 2991,  DOI: 10.1038/s41467-022-30687-9
      54
      Towards universal neural network potential for material discovery applicable to arbitrary combination of 45 elements
      Takamoto, So; Shinagawa, Chikashi; Motoki, Daisuke; Nakago, Kosuke; Li, Wenwen; Kurata, Iori; Watanabe, Taku; Yayama, Yoshihiro; Iriguchi, Hiroki; Asano, Yusuke; Onodera, Tasuku; Ishii, Takafumi; Kudo, Takao; Ono, Hideki; Sawada, Ryohto; Ishitani, Ryuichiro; Ong, Marc; Yamaguchi, Taiki; Kataoka, Toshiki; Hayashi, Akihide; Charoenphakdee, Nontawat; Ibuka, Takeshi
      Nature Communications (2022), 13 (1), 2991CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
      Abstr.: Computational material discovery is under intense study owing to its ability to explore the vast space of chem. systems. Neural network potentials (NNPs) have been shown to be particularly effective in conducting atomistic simulations for such purposes. However, existing NNPs are generally designed for narrow target materials, making them unsuitable for broader applications in material discovery. Here we report a development of universal NNP called PreFerred Potential (PFP), which is able to handle any combination of 45 elements. Particular emphasis is placed on the datasets, which include a diverse set of virtual structures used to attain the universality. We demonstrated the applicability of PFP in selected domains: lithium diffusion in LiFeSO4F, mol. adsorption in metal-org. frameworks, an order-disorder transition of Cu-Au alloys, and material discovery for a Fischer-Tropsch catalyst. They showcase the power of PFP, and this technol. provides a highly useful tool for material discovery.
    55. 55
      Kresse, G.; Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
      55
      Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
      Kresse, G.; Furthmuller, J.
      Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
      The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
    56. 56
      Kresse, G.; Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 1996, 54, 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
      56
      Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
      Kresse, G.; Furthmueller, J.
      Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
    57. 57
      Anisimov, V. I.; Aryasetiawan, F.; Lichtenstein, A. I. First-principles calculations of the electronic structure and spectra of strongly correlated systems: theLDA+Umethod. J. Phys.: Condens. Matter 1997, 9, 767– 808,  DOI: 10.1088/0953-8984/9/4/002
      57
      First-principles calculations of the electronic structure and spectra of strongly correlated systems: the LDA + U method
      Anisimov, Vladimir I.; Aryasetiawan, F.; Lichtenstein, A. I.
      Journal of Physics: Condensed Matter (1997), 9 (4), 767-808CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
      A review with 75 refs. A generalization of the local-d. approxn. (LDA) method for systems with strong Coulomb correlations is described which gives a correct description of the Mott insulators. The LDA + U method (U = Coulomb interaction parameter) takes into account orbital dependence of the Coulomb and exchange interactions which is absent in the LDA. The scheme can be regarded as a "first-principles" method because there are no adjustable parameters. When applied to the transition metal compds. and rare earth metal compds., the LDA + U method gives a qual. improvement compared with the LDA not only for excited-state properties such as energy gaps but also for ground-state properties such as magnetic moments and interat. exchange parameters. The orbital-dependent rotationally invariant LDA + U potential gives a correct orbital polarization and a corresponding Jahn-Teller distortion as well as polaron formation.
    58. 58
      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
      58
      Generalized gradient approximation made simple
      Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
      Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
    59. 59
      Perdew, J. P.; Ruzsinszky, A.; Csonka, G. I.; Vydrov, O. A.; Scuseria, G. E.; Constantin, L. A.; Zhou, X.; Burke, K. Restoring the density-gradient expansion for exchange in solids and surfaces. Phys. Rev. Lett. 2008, 100, 136406,  DOI: 10.1103/PhysRevLett.100.136406
      59
      Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces
      Perdew, John P.; Ruzsinszky, Adrienn; Csonka, Gabor I.; Vydrov, Oleg A.; Scuseria, Gustavo E.; Constantin, Lucian A.; Zhou, Xiaolan; Burke, Kieron
      Physical Review Letters (2008), 100 (13), 136406/1-136406/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Popular modern generalized gradient approxns. are biased toward the description of free-atom energies. Restoration of the first-principles gradient expansion for exchange over a wide range of d. gradients eliminates this bias. We introduce a revised Perdew-Burke-Ernzerhof generalized gradient approxn. that improves equil. properties of densely packed solids and their surfaces.
    60. 60
      Jain, A.; Hautier, G.; Ong, S. P.; Moore, C. J.; Fischer, C. C.; Persson, K. A.; Ceder, G. Formation enthalpies by mixing GGA and GGA+Ucalculations. Phys. Rev. B 2011, 84, 045115,  DOI: 10.1103/PhysRevB.84.045115
      There is no corresponding record for this reference.
    61. 61
      Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 2011, 44, 1272– 1276,  DOI: 10.1107/S0021889811038970
      61
      VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data
      Momma, Koichi; Izumi, Fujio
      Journal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acscentsci.4c00578.

    • SEM images of different LiMnO2 polymorphs, highlighted XRD patterns of orthorhombic and heat-treated LiMnO2, comparison of oxygen packing of orthorhombic and monoclinic layered LiMnO2, energy difference of LiMnO2 polymorphs obtained by theoretical calculations, STEM images of heat-treated LiMnO2, simulated XRD patterns with stacking fault analysis, structure factors and X-ray PDFs of different LiMnO2 polymorphs obtained by high-energy X-ray diffraction, charge/discharge curves of orthorhombic LiMnO2 before/after the preparation of carbon composited sample, charge/discharge curves and differential capacity plots of the as-prepared sample for monoclinic layered LiMnO2, cyclability of different LiMnO2 polymorphs at a rate of 10 mA g–1, comparison of electrode performance of heat-treated LiMnO2 and Li1.2Co0.13Ni0.13Mn0.54O2, comparison of quasi-open circuit voltage for heat-treated LiMnO2 (5th and 10th cycles), charge/discharge curves of LiNi0.835Co0.15Al0.015O2, structural evolution of different LiMnO2 polymorphs, simulated XRD patterns of cubic and tetragonal Li2Mn2O4 (Li1+xMn2O4), selected Rietveld-refined fits of structural models to the operando XRD data for heat-treated LiMnO2, selected XRD patterns from the operando XRD experiment, operando XRD pattern overlaid, STEM images of heat-treated LiMnO2 after cycle test, diagnostic plots of energies and forces obtained by DFT and UNNP calculations, characterization and electrochemistry of nanostructured LiMnO2 (PDF)


    Terms & Conditions

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