Halide Lithium Conductors: From Design and Synthesis to Application for All-Solid-State Batteries

All-solid-state lithium batteries (ASSLBs) based on solid-state electrolytes (SSEs) are considered as the next generation of energy storage devices due to their high energy density and safety. Halide SSEs have attracted attention due to their high oxidative stability, compatibility with oxide cathodes, and high ionic conductivity (>10–3 S·cm–1). Here, we introduce various halide SSEs and common synthesis methods. To design halide SSEs, we discuss the challenges faced by halide SSEs in terms of ion transport and electrochemical stability and present corresponding optimization strategies. Subsequently, the application of halide SSEs in high-specific-energy ASSLBs is demonstrated. Finally, we propose the key issues that need to be addressed and perspectives on future research of halide SSEs.