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Li‐rich Mn‐based layered oxides (LLO) hold great promise as cathode materials for lithium‐ion batteries (LIBs) due to their unique oxygen redox (OR) chemistry, which enables additional capacity. However, the LLOs face challenges related to the instability of their OR process due to the weak transition metal (TM)‐oxygen bond, leading to oxygen loss and irreversible phase transition that results in severe capacity and voltage decay. Herein, a synergistic electronic regulation strategy of surface and interior structures to enhance oxygen stability is proposed. In the interior of the materials, the local electrons around TM and O atoms may be delocalized by surrounding Mo atoms, facilitating the formation of stronger TM─O bonds at high voltages. Besides, on the surface, the highly reactive O atoms with lone pairs of electrons are passivated by additional TM atoms, which provides a more stable TM─O framework. Hence, this strategy stabilizes the oxygen and hinders TM migration, which enhances the reversibility in structural evolution, leading to increased capacity and voltage retention. This work presents an efficient approach to enhance the performance of LLOs through surface‐to‐interior electronic structure modulation, while also contributing to a deeper understanding of their redox reaction. [ABSTRACT FROM AUTHOR]

LiCoO2 is used as a cathode material for lithium‐ion batteries, however, cationic/anodic‐redox‐induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO2 to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg‐pillared LiCoO2. Dopant Mg ions, serving as pillars in the Li‐slab of LiCoO2, prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li‐Mg mixing structure at the surface of Mg‐pillared LiCoO2 is beneficial for eliminating the cathode‐electrolyte interphase overgrowth and phase transformation in the close‐to‐surface region. Mg‐pillared LiCoO2 exhibits a high capacity of 204 mAh g−1 at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0–4.6 V. In contrast, pristine LiCoO2 has a capacity retention of 14 % within the same voltage window. [ABSTRACT FROM AUTHOR]

Layered transition metal (TM) oxides have aroused enormous interest in both fundamental and applied cathode material research in the context of high energy‐density batteries. Although various mechanisms have been proposed to explain their significant initial capacity losses, the effect of the local structural defects on performance has been largely ignored. Herein, the stacking faults are visualized and their presence is correlated with the incomplete phase transition in Li2RuO3 to understand the significant abnormal capacity loss in the first cycle. The comprehensive performance evaluation, physical characterization and theoretical calculations indicate that the two types of stacking faults, the [100]//[11¯0] boundaries and the [110]//[11¯0] boundaries, lead to sluggish lithium diffusion and increasing stacking faults deteriorates the lithium insertion dynamics. These findings are helpful to understand the performance degradation of the layer‐structured oxides in which the anionic redox or the transition metal migration is not involved in electrochemical reactions. It is hoped that this research will also inspire new ideas for designing novel cathode materials and for improving the performance of existing materials by tuning the local structures or minimizing the local structural defects. [ABSTRACT FROM AUTHOR]

Sluggish kinetics and poor reversibility of cathode chemistry is the major challenge for magnesium batteries to achieve high volumetric capacity. Introduction of the cuprous ion (Cu+) as a charge carrier can decouple the magnesiation related energy storage from the cathode electrochemistry. Cu+ is generated from a fast equilibrium between copper selenide electrode and Mg electrolyte during standing time, rather than in the electrochemical process. A reversible chemical magnesiation/de‐magnesiation can be driven by this solid/liquid equilibrium. During a typical discharge process, Cu+ is reduced to Cu and drives the equilibrium to promote the magnesiation process. The reversible Cu to Cu+ redox promotes the recharge process. This novel Cu+ mediated cathode chemistry of Mg battery leads to a high reversible areal capacity of 12.5 mAh cm−2 with high mass loading (49.1 mg cm−2) of the electrode. 80 % capacity retention can be achieved for 200 cycles after a conditioning process. [ABSTRACT FROM AUTHOR]

Layered transition metal (TM) oxides have aroused enormous interest in both fundamental and applied cathode material research in the context of high energy‐density batteries. Although various mechanisms have been proposed to explain their significant initial capacity losses, the effect of the local structural defects on performance has been largely ignored. Herein, the stacking faults are visualized and their presence is correlated with the incomplete phase transition in Li2RuO3 to understand the significant abnormal capacity loss in the first cycle. The comprehensive performance evaluation, physical characterization and theoretical calculations indicate that the two types of stacking faults, the [100]//[11¯0] boundaries and the [110]//[11¯0] boundaries, lead to sluggish lithium diffusion and increasing stacking faults deteriorates the lithium insertion dynamics. These findings are helpful to understand the performance degradation of the layer‐structured oxides in which the anionic redox or the transition metal migration is not involved in electrochemical reactions. It is hoped that this research will also inspire new ideas for designing novel cathode materials and for improving the performance of existing materials by tuning the local structures or minimizing the local structural defects. [ABSTRACT FROM AUTHOR]