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

Abstract 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/Li 2 CO 3 , onto LiCoO 2 (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/Li 2 CO 3 enhances the interfacial stability between LCO and Li 10 GeP 2 S 12 as well as Li 3 PS 4 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 O 2 cathodes and other reducing gases such as H 2 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.