Cation configuration in transition-metal layered oxides

Abstract

<h2>Summary</h2> The cation configuration of transition-metal (TM) layered oxides used as cathode materials for batteries, which significantly affects their intrinsic performance, is extremely important for understanding their electrochemical behavior and remained unclear until now. Herein, the local cation configuration of a series of Mn-based Li-rich layered oxides (Mn-LLOs) was revealed thoroughly by statistical methods, and the influence of the cation configuration on the cationic/anionic redox was also elucidated. Using neutron and synchrotron X-ray pair distribution function combined with Monte Carlo simulation, the existence of Li₂MnO₃ rather than Li₂MnO₃-like crystal domain in all Mn-LLOs is revealed strongly, showing each Li atom in the TM layer is surrounded by six Mn atoms with no Ni atom to form a LiMn₆ unit, and the reversibility of oxygen redox is closely related with those local structure environments. This work provides insights for the cation configuration investigation of oxide materials and also sheds light on the understanding of the local structure-activity relationship.