Insights into the Oxide Cathode Active Material/Sulfide-Based Solid-State Electrolyte Interface in All-Solid-State Lithium Batteries: Coupling Mechanical and (Electro)chemical Perspectives

Abstract All-solid-state lithium batteries (ASSLBs) feature reliable safety, high energy density, and stable cycling, stepping into the key development and application stage. However, a main challenge impeding their further commercialization arises from the complex mechano-(electro)chemical coupling effects at the cathode active material (CAM)/solid-state electrolyte (SSE) interface, which critically governs interfacial contact integrity, ion transport efficiency, and overall cell performance and lifespan. Innovatively, this review decouples and independently analyzes two core degradation pathways: mechanical failure induced by stress accumulation and structural evolution and (electro)chemical degradation driven by space charge layer (SCL) formation, elemental diffusion, and interfacial reactions. Corresponding stabilization strategies are critically evaluated, including strain-mitigating designs such as single-crystal cathodes, near-zero-strain materials, deformable electrolytes, and pressure-adaptive assembly, complemented by (electro)chemical passivation through coating and buffer layers. Ultimately, this work elaborates in detail on the integrated coupling mechanisms, surveys advanced characterization techniques, and proposes future research directions, offering theoretical and methodological guidance for ASSLB development.