Halide-based materials and interfacial chemistry for solid-state batteries: From fundamentals to applications

The development of highly stable and highly ionic conductive solid state electrolytes is critical to next-generation all solid state batteries. This review provides a systematic overview of halide solid electrolytes, which combine high ionic conductivity (>1 mS/cm), wide electrochemical stability windows, and earth-abundant constituents, thereby addressing several limitations associated with sulfide- and oxide-based electrolytes. Different kinds of halide solid state electrolytes, interface challenges, advanced characterization techniques, computation-driven materials design strategies, and emerging concepts beyond halide chemistries are discussed. The aim of this review is to provide a comprehensive summary of inorganic halide solid state electrolytes for rechargeable lithium and sodium solid state batteries, with the expectation that these insights will support the understanding, rational design and further improvement of halide-based battery systems.