Heavy Fluorination via Ion Exchange Achieves High‐Performance Li–Mn–O–F Layered Cathode for Li‐Ion Batteries

Abstract Lithium‐excess manganese layered oxide Li 2 MnO 3 , attracts much attention as a cathode in Li‐ion batteries, due to the low cost and the ultrahigh theoretical capacity (≈460 mA h g −1 ). However, it delivers a low reversible practical capacity (<200 mA h g −1 ) due to the irreversible oxygen redox at high potentials (>4.5 V). Herein, heavy fluorination (9.5%) is successfully implemented in the layered anionic framework of a Li–Mn–O–F (LMOF) cathode through a unique ion‐exchange route. F substitution with O stabilizes the layered anionic framework, completely inhibits the O 2 evolution during the first cycle, and greatly enhances the reversibility of oxygen redox, delivering an ultrahigh reversible capacity of 389 mA h g −1 , which is 85% of the theoretical capacity of Li 2 MnO 3 . Moreover, it also induces a thin spinel shell coherently forming on the particle surface, which greatly improves the surface structure stability, making LMOF exhibit a superior cycling stability (a capacity retention of 91.8% after 120 cycles at 50 mA g −1 ) and excellent rate capability. These findings stress the importance of stabilizing the anionic framework in developing high‐performance low‐cost cathodes for next‐generation Li‐ion batteries.