Dual‐Function Modifications for High‐Stability Li‐Rich Cathode Toward Sulfide All‐Solid‐State Batteries

Abstract With the growing demand for high‐energy‐density lithium‐ion batteries, Li‐rich Mn‐based layered oxide (LLO) cathodes with high specific capacity and low cost receive significant attention in conventional liquid lithium‐ion batteries. However, LLO is rarely used in sulfide all‐solid‐state lithium batteries (ASSLBs) because of severe interfacial side reactions with sulfide solid electrolytes (SEs), especially at a high operation voltage of 4.8 V (vs Li/Li⁺). In this work, a dual‐function modification strategy is proposed to enable electrochemically stable LLO in sulfide ASSLBs. The covalent Ru─O bond formed by Ru‐doping can not only stabilize lattice oxygen, preventing further interfacial decomposition involving oxygen, but also enhance the ability of Li diffusion in Li₂MnO₃ component, and then stimulate the activation of Li₂MnO₃ phase. Meanwhile, the surface sulfidation strategy establishes a highly stable interface, contributing to the rapid ionic transport at LLO/LPSCl interface. Results show that the modified LLO in sulfide ASSLBs delivers two times higher initial discharge capacity and an extra‐long life of 2022 cycles of up to 4.2 V (vs Li–In) (with >70% capacity retention at 1 C). This research enriches the strategies for improving interfacial compatibility between LLO cathodes and sulfide SEs, thus providing new inspiration for guiding the application of LLO in sulfide ASSLBs.