Converting and Fabricating LiCoO 2 Cathode Material into a Disordered Rocksalt Surface Modification Layer to Enhance Interfacial Stability of High‐Voltage Cathode

Abstract Surface coating acts as an effective strategy to enhance the interfacial stability of high‐voltage cathode, but yet there remains substantial potential value in exploring optimal materials and methods. Herein, we convert spent LiCoO 2 (LCO) into nanosized disordered rocksalt‐phase (DS) coating material, which exhibits considerable Li + conductivity and high lattice‐coherent compatibility with LCO. Subsequently, using a facile and scalable high‐speed mechanofusion technology, we construct a continuous, uniform, and tightly bound DS coating layer onto LCO, denoted as DS@LCO cathode. Benefiting from the nucleophilic reaction between fluorinated electrolyte and reactive oxygen released from DS coating layer, a stable cathode‐electrolyte interphase (CEI) film is achieved, with an outer LiF‐rich protective shield and inner flexible fluorinated polymer. Coupled with the lattice‐coherent DS coating layer and reinforced CEI film, the hybrid surface architecture synergistically enhances the interfacial stability, thermal safety, and electrochemical performance of DS@LCO cathode. As a result, a stable operation of DS@LCO half‐cell is achieved at 4.6 V (90.1% capacity retention after 250 cycles). Long‐life and high‐energy‐density (1032 Wh L −1 ) pouch cells are harvested, retaining over 86% capacity after 1000 cycles. This coating/CEI‐coupled interface design provides a sustainable and scalable surface modification route for the development of high‐voltage cathodes with enhanced interfacial stability.