Reducing Gases Triggered Cathode Surface Reconstruction for Stable Cathode–Electrolyte Interface in Practical All‐Solid‐State Lithium Batteries

The interfacial compatibility between cathodes and sulfide solid-electrolytes (SEs) is a critical limiting factor of electrochemical performance in all-solid-state lithium-ion batteries (ASSLBs). This work presents a gas-solid interface reduction reaction (GSIRR), aiming to mitigate the reactivity of surface oxygen by inducing a surface reconstruction layer (SRL) . The application of a SRL, CoO/Li₂ CO₃ , onto LiCoO₂ (LCO) cathode results in impressive outcomes, including high capacity (149.7 mAh g^-1 ), remarkable cyclability (retention of 84.63% over 400 cycles at 0.2 C), outstanding rate capability (86.1 mAh g^-1 at 2 C), and exceptional stability in high-loading cathode (28.97 and 23.45 mg cm^-2 ) within ASSLBs. Furthermore, the SRL CoO/Li₂ CO₃ enhances the interfacial stability between LCO and Li₁₀ GeP₂ S₁₂ as well as Li₃ PS₄ SEs. Significantly, the experiments suggest that the GSIRR mechanism can be broadly applied, not only to LCO cathodes but also to LiNi_0.8 Co_0.1 Mn_0.1 O₂ cathodes and other reducing gases such as H₂ S and CO, indicating its practical universality. This study highlights the significant influence of the surface chemistry of the oxide cathode on interfacial compatibility, and introduces a surface reconstruction strategy based on the GSIRR process as a promising avenue for designing enhanced ASSLBs.