In Situ Surface Self‐Reconstruction Strategies in Li‐Rich Mn‐Based Layered Cathodes for Energy‐Dense Li‐Ion Batteries

Lithium-rich manganese-based layered oxides (LROs) are standing out as cathode materials of lithium-ion batteries (LIBs) due to merits on both capacity (>250 mAh g(-1)) and operation voltage (approximate to 3.6 V). However, the applications of LROs are plagued by almost inevitable degradation of structure, in which electrode surface bears the brunt as the primacy barrier for Li+ transport. Plenty of surface modification strategies are proposed to stabilize the structure and in situ self-reconstruction strategies with atomic level connection to bulk structures provide robust layers to prevent the degradation. Herein, a critical review focusing on in situ surface reconstruction of LROs is summarized. It is started from the overview of LROs and then the surface challenges including lattice oxygen release, phase transformation, transition metal ions dissolution, and interfacial side reactions are further discussed. In situ self-reconstruction strategies are emphasized to alleviate the performance degradation of LROs, from creating oxygen vacancies to synthesizing layered-spinel or layered-rocksalt heterogeneous structures. Among these approaches, synthesis and characterization methods, formation mechanisms and roles to stabilize the structures are highlighted. Finally, the prospects from the aspects of precise/large scale preparations, interphase design between electrolytes and electrodes, and in-operando characterization approaches for the commercialization of LROs are provided.