Another Strategy,Detouring Potential Decay by Fast Completion of Cation Mixing

The Li‐rich layer‐structured oxides are regarded one of the most promising candidates of cathode materials for high energy‐density Li‐ion batteries. However, the uninterrupted migration of the transition metal (TM) ions during cycling and the resultant continuous fading of their discharge potentials bring challenges to the battery design and impede their commercial applications. Various efforts have been taken to suppress the migration of the TM ions such as surface modification and elemental substitution, but no success has been achieved to date. Another strategy hereby is proposed to address these issues, in which the TM migration is promoted and the layered material is transformed to a rocksalt in the first few charge/discharge cycles by specially designing a novel Li‐rich layer‐structured Li_1.2Mo_0.6Fe_0.2O₂ on the basis of density functional theory calculations. With such, the continuous falling of the discharge potential is detoured due to enhanced completion of the cation mixing. In‐depth studies such as aberration‐corrected scanning transmission electron microscopy confirm the drastic structural change at the atomic scale, and in situ X‐ray absorption spectroscopy and Mössbauer spectroscopy clarify its charge compensation mechanism. This new strategy provides revelation for the development of the Li‐rich layered oxides with mitigated potential decay and a longer lifespan.     

Understanding Performance Degradation in Cation‐Disordered Rock‐Salt Oxide Cathodes

The collective redox activities of transition‐metal (TM) cations and oxygen anions have been shown to increase charge storage capacity in both Li‐rich layered and cation‐disordered rock‐salt cathodes. Repeated cycling involving anionic redox is known to trigger TM migration and phase transformation in layered Li‐ and Mn‐rich (LMR) oxides, however, detailed mechanistic understanding on the recently discovered Li‐rich rock‐salt cathodes is largely missing. The present study systematically investigates the effect of oxygen redox on a Li_1.3Nb_0.3Mn_0.4O₂ cathode and demonstrates that performance deterioration is directly correlated to the extent of oxygen redox. It is shown that voltage fade and hysteresis begin only after initiating anionic redox at high voltages, which grows progressively with either deeper oxidation of oxygen at higher potential or extended cycling. In contrast to what is reported on layered LMR oxides, extensive TM reduction is observed but phase transition is not detected in the cycled oxide. A densification/degradation mechanism is proposed accordingly which elucidates how a unique combination of extensive chemical reduction of TM and reduced quality of the Li percolation network in cation‐disordered rock‐salts can lead to performance degradation in these newer cathodes with 3D Li migration pathways. Design strategies to achieve balanced capacity and stability are also discussed.     

Unraveling the Voltage Decay Phenomenon in Li‐Rich Layered Oxide Cathode of No Oxygen Activity

Extensive efforts have been devoted to unraveling the true cause of voltage decay in Li, Mn‐rich layered oxides. An initial consensus was reached on structural rearrangement, then leaned toward the newly discovered lattice oxygen activity. It is challenging to differentiate their explicit roles because these events typically coexist during the electrochemical reaction of most Li‐rich layered oxides. Here, the voltage decay behavior is probed in Li_1.2Ni_0.2Ru_0.6O₂, a structurally and electrochemically relevant compound to Li, Mn‐rich layered oxide, but of no oxygen activity. Such intriguing characteristics allow the explicit decoupling of the contribution of transition metal migration and lattice oxygen activity to voltage decay in Li‐rich layered oxides. The results demonstrate that the microstructural evolution, mainly originating from transition metal migration, is a direct cause of voltage decay, and lattice oxygen activity likely accelerates the decay.     

Countering Voltage Decay and Capacity Fading of Lithium‐Rich Cathode Material at 60 °C by Hybrid Surface Protection Layers

Li‐rich layered metal oxides have attracted much attention for their high energy density but still endure severe capacity fading and voltage decay during cycling, especially at elevated temperature. Here, facile surface treatment of Li_1.17Ni_0.17Co_0.17Mn_0.5O₂ (0.4Li₂MnO₃·0.6LiNi_1/3Co_1/3Mn_1/3O₂) spherical cathode material is designed to address these drawbacks by hybrid surface protection layers composed of Mg²⁺ pillar and Li‐Mg‐PO₄ layer. As a result, the surface coated Li‐rich cathode material exhibits much enhanced cycling stability at 60 °C, maintaining 72.6% capacity retention (180 mAh g^?1) between 3.0 and 4.7 V after 250 cycles. More importantly, 88.7% average discharge voltage retention can be obtained after the rigorous cycle test. The strategy developed here with novel hydrid surface protection effect can provide a vital approach to inhibit the undesired side reactions and structural deterioration of Li‐rich cathode materials and may also be useful for other layered oxides to increase their cycling stability at elevated temperature.     

Insight of a Phase Compatible Surface Coating for Long‐Durable Li‐Rich Layered Oxide Cathode

Li‐rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO₂ and LiMn₂O₄; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high‐energy lithium‐ion batteries. Herein, hexagonal La_0.8Sr_0.2MnO_3?y (LSM) is used as a protective and phase‐compatible surface layer to stabilize the Li‐rich layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LM) cathode material. The LSM is Mn? O? M bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM‐coated LM delivers an enhanced reversible capacity of 202 mAh g^?1 at 1 C (260 mA g^?1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g^?1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next‐generation of high‐energy Li‐ion batteries.     

Suppressing Voltage Fading of Li‐Rich Oxide Cathode via Building a Well‐Protected and Partially‐Protonated Surface by Polyacrylic Acid Binder for Cycle‐Stable Li‐Ion Batteries

Li‐rich manganese based oxides (LRMOs) are considered an attractive high‐capacity cathode for advanced Li‐ion batteries; however, their poor cyclability and gradual voltage fading have hindered their practical applications. Herein, an efficient and facile strategy is proposed to stabilize the lattice structure of LRMOs by surface modification of polyacrylic acid (PAA). The PAA‐coated LRMO electrode exhibits only 104 mV of the voltage fading after 100 cycles and 88% capacity retention over 500 cycles. The structural stability is attributed to the carboxyl groups in PAA chains reacting with oxygen species on the surface of LRMO to form a uniform and tightly coated film, which significantly suppresses the dissolution of transition metal elements from the cathode materials into the electrolyte. Importantly, a H⁺/Li⁺ exchange reaction takes place between the LRMO and PAA, generating a proton‐doped surface layer. Density functional theory calculations and experimental evidence demonstrates that the H⁺ ions in the surface lattice efficiently inhibit the migration of transition metal ions, leading to a stabilized lattice structure. This surface modification approach may provide a new route to building a stable Li‐rich oxide cathode with high capacity retention and low voltage fading for practical Li‐ion battery applications.     

Eliminating Transition Metal Migration and Anionic Redox to Understand Voltage Hysteresis of Lithium‐Rich Layered Oxides

Lithium‐rich layered oxides are promising candidate cathode materials for the Li‐ion batteries with energy densities above 300 Wh kg^?1. However, issues such as the voltage hysteresis and decay hinder their commercial applications. Due to the entanglement of the transition metal (TM) migration and the anionic redox upon lithium extraction at high potentials, it is difficult to recognize the origin of these issues in conventional Li‐rich layered oxides. Herein, Li₂MoO₃ is chosen since prototype material to uncover the reason for the voltage hysteresis as the TM migration and anionic redox can be eliminated below 3.6 V versus Li⁺/Li in this material. On the basis of comprehensive investigations by neutron powder diffraction, scanning transmission electron microscopy, synchrotron X‐ray absorption spectroscopy, and density functional theory calculations, it is clarified that the ordering–disordering transformation of the Mo₃O₁₃ clusters induced by the intralayer Mo migration is responsible for the voltage hysteresis in the first cycle; the hysteresis can take place even without the anionic redox or the interlayer Mo migration. A similar suggestion is drawn for its iso‐structured Li₂RuO₃ (C2/c). These findings are useful for understanding of the voltage hysteresis in other complicated Li‐rich layered oxides.     

Review on Challenges and Recent Advances in the Electrochemical Performance of High Capacity Li‐ and Mn‐Rich Cathode Materials for Li‐Ion Batteries

Li and Mn‐rich layered oxides, xLi₂MnO₃·(1–x)LiMO₂ (M=Ni, Mn, Co), are promising cathode materials for Li‐ion batteries because of their high specific capacity that can exceed 250 mA h g^?1. However, these materials suffer from high 1^st cycle irreversible capacity, gradual capacity fading, low rate capability, a substantial charge‐discharge voltage hysteresis, and a large average discharge voltage decay during cycling. The latter detrimental phenomenon is ascribed to irreversible structural transformations upon cycling of these cathodes related to potentials ≥4.5 V required for their charging. Transition metal inactivation along with impedance increase and partial layered‐to‐spinel transformation during cycling are possible reasons for the detrimental voltage fade. Doping of Li, Mn‐rich materials by Na, Mg, Al, Fe, Co, Ru, etc. is useful for stabilizing capacity and mitigating the discharge‐voltage decay of xLi₂MnO₃·(1–x)LiMO₂ electrodes. Surface modifications by thin coatings of Al₂O₃, V₂O₅, AlF₃, AlPO₄, etc. or by gas treatment (for instance, by NH₃) can also enhance voltage and capacity stability during cycling. This paper describes the recent literature results and ongoing efforts from our groups to improve the performance of Li, Mn‐rich materials. Focus is also on preparation of cobalt‐free cathodes, which are integrated layered‐spinel materials with high reversible capacity and stable performance.     

Site‐Selective In Situ Electrochemical Doping for Mn‐Rich Layered Oxide Cathode Materials in Lithium‐Ion Batteries

Various doped materials have been investigated to improve the structural stability of layered transition metal oxides for lithium‐ion batteries. Most doped materials are obtained through solid state methods, in which the doping of cations is not strictly site selective. This paper demonstrates, for the first time, an in situ electrochemical site‐selective doping process that selectively substitutes Li⁺ at Li sites in Mn‐rich layered oxides with Mg²⁺. Mg²⁺ cations are electrochemically intercalated into Li sites in delithiated Mn‐rich layered oxides, resulting in the formation of [Li_1?xMg_y][Mn_1?zM_z]O₂ (M = Co and Ni). This Mg²⁺ intercalation is irreversible, leading to the favorable doping of Mg²⁺ at the Li sites. More interestingly, the amount of intercalated Mg²⁺ dopants increases with the increasing amount of Mn in Li_1?x[Mn_1?zM_z]O₂, which is attributed to the fact that the Mn‐to‐O electron transfer enhances the attractive interaction between Mg²⁺ dopants and electronegative O^δ? atoms. Moreover, Mg²⁺ at the Li sites in layered oxides suppresses cation mixing during cycling, resulting in markedly improved capacity retention over 200 cycles. The first‐principle calculations further clarify the role of Mg²⁺ in reduced cation mixing during cycling. The new concept of in situ electrochemical doping provides a new avenue for the development of various selectively doped materials.     

Al Doping for Mitigating the Capacity Fading and Voltage Decay of Layered Li and Mn‐Rich Cathodes for Li‐Ion Batteries

Li and Mn‐rich layered cathodes, despite their high specific capacity, suffer from capacity fading and discharge voltage decay upon cycling. Both specific capacity and discharge voltage of Li and Mn‐rich cathodes are stabilized upon cycling by optimized Al doping. Doping Li and Mn‐rich cathode materials Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ by Al on the account of manganese (as reflected by their stoichiometry) results in a decrease in their specific capacity but increases pronouncedly their stability upon cycling. Li_1.2Ni_0.16Mn_0.51Al_0.05Co_0.08O₂ exhibits 96% capacity retention as compared to 68% capacity retention for Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ after 100 cycles. This doping also reduces the decrease in the average discharge voltage upon cycling, which is the longstanding fatal drawback of these Li and Mn‐rich cathode materials. The electrochemical impedance study indicates that doping by Al has a surface stabilization effect on these cathode materials. The structural analysis of cycled electrodes by Raman spectroscopy suggests that Al doping also has a bulk stabilizing effect on the layered LiMO₂ phase resulting in the better electrochemical performance of Al doped cathode materials as compared to the undoped counterpart. Results from a prolonged systematic work on these cathode materials are presented and the best results that have ever been obtained are reported.     

Nickel‐Rich and Lithium‐Rich Layered Oxide Cathodes: Progress and Perspectives

Ni‐rich layered oxides and Li‐rich layered oxides are topics of much research interest as cathodes for Li‐ion batteries due to their low cost and higher discharge capacities compared to those of LiCoO₂ and LiMn₂O₄. However, Ni‐rich layered oxides have several pitfalls, including difficulty in synthesizing a well‐ordered material with all Ni³⁺ ions, poor cyclability, moisture sensitivity, a thermal runaway reaction, and formation of a harmful surface layer caused by side reactions with the electrolyte. Recent efforts towards Ni‐rich layered oxides have centered on optimizing the composition and processing conditions to obtain controlled bulk and surface compositions to overcome the capacity fade. Li‐rich layered oxides also have negative aspects, including oxygen loss from the lattice during first charge, a large first cycle irreversible capacity loss, poor rate capability, side reactions with the electrolyte, low tap density, and voltage decay during extended cycling. Recent work on Li‐rich layered oxides has focused on understanding the surface and bulk structures and eliminating the undesirable properties. Followed by a brief introduction, an account of recent developments on the understanding and performance gains of Ni‐rich and Li‐rich layered oxide cathodes is provided, along with future research directions.     

Stabilized Co‐Free Li‐Rich Oxide Cathode Particles with An Artificial Surface Prereconstruction

Li‐rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g^?1. However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well‐known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full‐cell performance degradation. Herein, an artificial surface prereconstruction (ASR) for Li_1.2Mn_0.6Ni_0.2O₂ particles with a molten‐molybdate leaching is conducted, which creates a crystal‐dense anion‐redox‐free LiMn_1.5Ni_0.5O₄ shell that completely encloses the LXMO lattice (ASR‐LXMO). Differential electrochemical mass spectroscopy and soft X‐ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR‐LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR‐LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g^?1 with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full‐cell matched with a commercial graphite anode and lean (2 g A^?1 h^?1) electrolyte, ASR‐LXMO shows high capacity retention of 76% after 125 cycles in full‐cell cycling.     

An Ion‐Exchange Promoted Phase Transition in a Li‐Excess Layered Cathode Material for High‐Performance Lithium Ion Batteries

A new approach to intentionally induce phase transition of Li‐excess layered cathode materials for high‐performance lithium ion batteries is reported. In high contrast to the limited layered‐to‐spinel phase transformation that occurred during in situ electrochemical cycles, a Li‐excess layered Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ is completely converted to a Li₄Mn₅O₁₂‐type spinel product via ex situ ion‐exchanges and a post‐annealing process. Such a layered‐to‐spinel phase conversion is examined using in situ X‐ray diffraction and in situ high‐resolution transmission electron microscopy. It is found that generation of sufficient lithium ion vacancies within the Li‐excess layered oxide plays a critical role for realizing a complete phase transition. The newly formed spinel material exhibits initial discharge capacities of 313.6, 267.2, 204.0, and 126.3 mAh g^?1 when cycled at 0.1, 0.5, 1, and 5 C (1 C = 250 mA g^?1), respectively, and can retain a specific capacity of 197.5 mAh g^?1 at 1 C after 100 electrochemical cycles, demonstrating remarkably improved rate capability and cycling stability in comparison with the original Li‐excess layered cathode materials. This work sheds light on fundamental understanding of phase transitions within Li‐excess layered oxides. It also provides a novel route for tailoring electrochemical performance of Li‐excess layered cathode materials for high‐capacity lithium ion batteries.     

Structural Changes in Li2MnO3 Cathode Material for Li‐Ion Batteries

Structural changes in Li₂MnO₃ cathode material for rechargeable Li‐ion batteries are investigated during the first and 33^rd cycles. It is found that both the participation of oxygen anions in redox processes and Li⁺‐H⁺ exchange play an important role in the electrochemistry of Li₂MnO₃. During activation, oxygen removal from the material along with Li gives rise to the formation of a layered MnO₂‐type structure, while the presence of protons in the interslab region, as a result of electrolyte oxidation and Li⁺‐H⁺ exchange, alters the stacking sequence of oxygen layers. Li re‐insertion by exchanging already present protons reverts the stacking sequence of oxygen layers. The re‐lithiated structure closely resembles the parent Li₂MnO₃, except that it contains less Li and O. Mn⁴⁺ ions remain electrochemically inactive at all times. Irreversible oxygen release occurs only during activation of the material in the first cycle. During subsequent cycles, electrochemical processes seem to involve unusual redox processes of oxygen anions of active material along with the repetitive, irreversible oxidation of electrolyte species. The deteriorating electrochemical performance of Li₂MnO₃ upon cycling is attributed to the structural degradation caused by repetitive shearing of oxygen layers.     

Lithiophilic CuO Nanoflowers on Ti‐Mesh Inducing Lithium Lateral Plating Enabling Stable Lithium‐Metal Anodes with Ultrahigh Rates and Ultralong Cycle Life

Lithium (Li) metal anodes are promising candidates for high‐energy‐density batteries. However, uncontrollable dendritic plating behavior and infinite volume expansion are hindering their practical applications. Herein, a novel CuO@Ti‐mesh (CTM) is prepared by microwave‐assisted reactions, followed by pressing on Li wafers, leading to Li/CuO@Ti‐mesh (LCTM) composite anodes. The lithiophilic CuO nanoflowers on Ti‐mesh provides evenly distributed nucleation sites, inducing uniform Li‐ion lateral plating, which can effectively inhibit the growth of Li dendrites and volume expansion during cycling. The as‐prepared LCTM composite anode exhibits high Coulombic efficiency (CE) of 94.2% at 10 mA cm^‐2 over 90 cycles. Meanwhile, the LCTM anode shows a low overpotential of 50 mV at 10 mA cm^‐2 over 16 000 cycles and a low overpotential of 90 and 250 mV even at ultrahigh current densities of 20 and 40 mA cm^‐2. When paired with Li₄Ti₅O₁₂ (LTO), it enhances the capacity retention of LTO/Li wafer full cells by about two times from 36.6% to 73.0% and 42.0% to 80.0% at 5C and 10C with long‐term cycling. It is hoped that this LCTM anode with ultrahigh rates and ultralong cycle life may put Li‐metal anode forward to practical applications, such as in Li–S, Li‐air batteries, etc.     

Controlled Atomic Solubility in Mn‐Rich Composite Material to Achieve Superior Electrochemical Performance for Li‐Ion Batteries

The quest for high energy density and high power density electrode materials for lithium‐ion batteries has been intensified to meet strongly growing demand for powering electric vehicles. Conventional layered oxides such as Co‐rich LiCoO₂ and Ni‐rich Li(Ni_xMn_yCo_z)O₂ that rely on only transition metal redox reaction have been faced with growing constraints due to soaring price on cobalt. Therefore, Mn‐rich electrode materials excluding cobalt would be desirable with respect to available resources and low cost. Here, the strategy of achieving both high energy density and high power density in Mn‐rich electrode materials by controlling the solubility of atoms between phases in a composite is reported. The resulting Mn‐rich material that is composed of defective spinel phase and partially cation‐disordered layered phase can achieve the highest energy density, ≈1100 W h kg^?1 with superior power capability up to 10C rate (3 A g^?1) among other reported Mn‐rich materials. This approach provides new opportunities to design Mn‐rich electrode materials that can achieve high energy density and high power density for Li‐ion batteries.     

Lithium/Oxygen Incorporation and Microstructural Evolution during Synthesis of Li‐Rich Layered Li[Li0.2Ni0.2Mn0.6]O2 Oxides

As promising cathode materials, the lithium‐excess 3d‐transition‐metal layered oxides can deliver much higher capacities (>250 mAh g^?1 at 0.1 C) than the current commercial layered oxide materials (≈180 mAh g^?1 at 0.1 C) used in lithium ion batteries. Unfortunately, the original formation mechanism of these layered oxides during synthesis is not completely elucidated, that is, how is lithium and oxygen inserted into the matrix structure of the precursor during lithiation reaction? Here, a promising and practical method, a coprecipitation route followed by a microwave heating process, for controllable synthesis of cobalt‐free lithium‐excess layered compounds is reported. A series of the consistent results unambiguously confirms that oxygen atoms are successively incorporated into the precursor obtained by a coprecipitation process to maintain electroneutrality and to provide the coordination sites for inserted Li ions and transition metal cations via a high‐temperature lithiation. It is found that the electrochemical performances of the cathode materials are strongly related to the phase composition and preparation procedure. The monoclinic layered Li[Li_0.2Ni_0.2Mn_0.6]O₂ cathode materials with state‐of‐the‐art electrochemical performance and comparably high discharge capacities of 171 mAh g^?1 at 10 C are obtained by microwave annealing at 750 °C for 2 h.     

Ti‐Gradient Doping to Stabilize Layered Surface Structure for High Performance High‐Ni Oxide Cathode of Li‐Ion Battery

High‐Ni layered oxide cathodes are considered to be one of the most promising cathodes for high‐energy‐density lithium‐ion batteries due to their high capacity and low cost. However, surfice residues, such as NiO‐type rock‐salt phase and Li₂CO₃, are often formed at the particle surface due to the high reactivity of Ni³⁺, and inevitably result in an inferior electrochemical performance, hindering the practical application. Herein, unprecedentedly clean surfaces without any surfice residues are obtained in a representative LiNi_0.8Co_0.2O₂ cathode by Ti‐gradient doping. High‐resolution transmission electron microscopy (TEM) reveals that the particle surface is composed of a disordered layered phase (≈6 nm in thickness) with the same rhombohedra structure as its interior. The formation of this disordered layered phase at the particle surface is electrochemically favored. It leads to the highest rate capacity ever reported and a superior cycling stability. First‐principles calculations further confirm that the excellent electrochemical performance has roots in the excellent chemical/structural stability of such a disordered layered structure, mainly arising from the improved robustness of the oxygen framework by Ti doping. This strategy of constructing the disordered layered phase at the particle surface could be extended to other high‐Ni layered transition metal oxides, which will contribute to the enhancement of their electrochemical performance.     

3D Cube‐Maze‐Like Li‐Rich Layered Cathodes Assembled from 2D Porous Nanosheets for Enhanced Cycle Stability and Rate Capability of Lithium‐Ion Batteries

Li‐rich oxide is a promising candidate for the cathodes of next‐generation lithium‐ion batteries. However, its utilization is restricted by cycling instability and inferior rate capability. To tackle these issues, three‐dimensional (3D), hierarchical, cube‐maze‐like Li‐rich cathodes assembled from two‐dimensional (2D), thin nanosheets with exposed {010} active planes, are developed by a facile hydrothermal approach. Benefiting from their unique architecture, 3D cube‐maze‐like cathodes demonstrate a superior reversible capacity (285.3 mAh g^?1 at 0.1 C, 133.4 mAh g^?1 at 20.0 C) and a great cycle stability (capacity retention of 87.4% after 400 cycles at 2.0 C, 85.2% after 600 cycles and 75.0% after 1200 cycles at 20.0 C). When this material is matched with a graphite anode, the full cell achieves a remarkable discharge capacity (275.2 mAh g^?1 at 0.1 C) and stable cycling behavior (capacity retention of 88.7% after 100 cycles at 5.0 C, capacity retention of 84.8% after 100 cycles at 20.0 C). The present work proposes an accessible way to construct 3D hierarchical architecture assembled from 2D nanosheets with exposed high‐energy active {010} planes and verifies its validity for advanced Li‐rich cathodes.     

A Novel Strategy to Suppress Capacity and Voltage Fading of Li‐ and Mn‐Rich Layered Oxide Cathode Material for Lithium‐Ion Batteries

Poor cycling stability is one of the key scientific issues needing to be solved for Li‐ and Mn‐rich layered oxide cathode. In this paper, sodium carboxymethyl cellulose (CMC) is first used as a novel binder in Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode to enhance its cycling stability. Electrochemical performance is conducted by galvanostatic charge and discharge. Structure and morphology are characterized by X‐ray diffraction, scanning electronic microscopy, high‐resolution transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results reveal that the CMC as binder can not only stabilize the electrode structure by preventing the electrode materials to detach from the current collector but also suppress the voltage fading of the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode due to Na⁺ ions doping. Most importantly, the dissolution of metal elements from the cathode materials into the electrolyte is also inhibited.