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.