Sublattice engineering and crystal system design: microscopic pathways to enhanced performance in halide solid-state electrolytes

Halide solid-state electrolytes (HSSEs) hold great promise for all-solid-state batteries, but their ionic conductivity and electrochemical stability still remain key challenges in practical applications. This review systematically links the evolutionary trajectory of HSSEs, crystal structure–property relationships across different halide systems, sublattice engineering strategies, and rational crystal system design as new synergistic pathways to achieve significantly enhanced electrochemical performance. Finally, we also discuss challenges and machine learning for halide development.