Polymer‐Sulfide Composite Solid Electrolytes: Design, Interfacial Engineering, and Performance Optimization for All‐Solid‐State Lithium‐Ion Batteries

Driven by the dual demands for high energy density and intrinsic safety in next‐generation power systems, all‐solid‐state lithium‐ion batteries (ASSLIBs) using nonflammable solid‐state electrolytes have garnered significant attention. Among the candidates, sulfide‐based solid electrolytes (SSEs) are particularly promising due to their high ionic conductivity and soft mechanical properties. However, challenges such as their sensitivity to moisture and oxygen, electrochemical instability, and poor interfacial contact with electrodes hinder their practical application. To address these bottlenecks, this review highlights recent advances in material design and interfacial engineering of sulfide‐incorporated polymer matrix and summarizes how the introduction of sulfides into binders, gel polymers, and related systems improves interfacial electrochemical properties in ASSLIBs, along with the underlying mechanisms governing their electrochemical performance. In addition, we provide an in‐depth discussion of how embedding sulfide solid electrolytes into polymer matrix enables the construction of 3D ion transport networks, elucidating how interfacial energy barrier modulation and space‐charge layer formation enhance electrochemical stability and how multilayer barrier architectures contribute to improved environmental tolerance. We believe that our work will provide both theoretical insights and a technological roadmap for the development of high‐performance ASSLIBs.