Surface Lattice Modulation Enables Stable Cycling of High‐Loading All‐solid‐state Batteries at High Voltages

Halide solid electrolytes, known for their high ionic conductivity at room temperature and good oxidative stability, face notable challenges in all-solid-state Li-ion batteries (ASSBs), especially with unstable cathode/solid electrolyte (SE) interface and increasing interfacial resistance during cycling. In this work, we have developed an Al³⁺-doped, cation-disordered epitaxial nanolayer on the LiCoO₂ surface by reacting it with an artificially constructed AlPO₄ nanoshell; this lithium-deficient layer featuring a rock-salt-like phase effectively suppresses oxidative decomposition of Li₃InCl₆ electrolyte and stabilizes the cathode/SE interface at 4.5 V. The ASSBs with the halide electrolyte Li₃InCl₆ and a high-loading LiCoO₂ cathode demonstrated high discharge capacity and long cycling life from 3 to 4.5 V. Our findings emphasize the importance of specialized cathode surface modification in preventing SE degradation and achieving stable cycling of halide-based ASSBs at high voltages.