Surface Nonbonding Oxygen State Regulation for Reversible Anionic Redox Chemistry in Li‐rich Mn‐based Layered Oxides

Activated by the Li‐O‐Li configuration with nonbonding O2p state (lO2p), anionic redox reaction (ARR) in Li‐rich layered oxides (LLOs) contributes to additional capacity but exhibits significant irreversibility, leading to severe surface oxygen loss. Herein, surface nonbonding oxygen state (SNBOS) is regulated by the integrated surface structure engineering to suppress surface oxygen loss and enhance the reversibility of ARR. On the outermost layer, the conversion of layered structure into a LiLaO2 layer and spinel phase structure eliminates lO2p, thereby preventing the activation of ARR and suppressing side reaction between electrolyte and oxidized oxygen ions. Besides, by introducing 5d metal La on the near surface, the energy of lO2p is decreased corresponding to the increased charge‐transfer gap Δ and the d‐d coulomb repulsion term U is reduced, making U/2 decrease close to Δ and enhancing ARR reversibility. Furthermore, it’s demonstrated that the oxidized oxygen of the modified sample cannot become O2 gas and escape, but rather exists more in the form of high‐valance oxygen dimer anions O_2^(n‐), reducing the reaction depth of surface ARR and inhibiting oxygen loss. Therefore, the designed material demonstrates outstanding cycling stability and kinetics performance.