Converting and Fabricating LiCoO2 Cathode Material into a Disordered Rocksalt Surface Modification Layer to Enhance Interfacial Stability of High‐Voltage Cathode

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 LiCoO2 (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.