An In Situ Near‐Surface Reconstruction Strategy Endowing Lithium‐Rich Oxides with Li/O Dual Vacancies and Spinel‐Carbon Dual Coating Layers Toward High Energy Density Cathode

AbstractLi‐rich cathode materials (LRMs) are regarded as the key cathode candidates for next‐generation lithium‐ion batteries(LIBs) because of their high specific capacity and environmental friendliness. However, LRMs encounter poor cyclability and low initial coulombic efficiency (ICE) hindering their practical application. Herein, a general near‐surface in situ reconstruction strategy is proposed of constructing the Li/O dual vacancies and spinel‐carbon dual coating layers on the surface of LRMs concurrently to improve Li+ storage performance. The as‐prepared LRMs exhibit a greatly strengthened specific capacity of 283 mAh g−1 with an enhanced ICE of 94% and long‐term cyclability of 91% retention after 200 cycles compared with the pristine LRMs (212 mAh g−1 with an ICE of 65%, 76% retention after 200 cycles). Furthermore, it is theoretically revealed that O vacancies (Ov) prefer to occur at the interface of the C2/m and Rm phases to mitigate lattice stress, rather the O sites in individual C2/m or Rm phase with more coordinated atoms. Besides, Li ions exhibit lower migration energy from C2/m phase to Rm phase with the Ov located at the lattice interface. Therefore, this strategy opens a new avenue in the design perspective of the LRMs’ near‐surface for high‐energy‐density LIBs.