The chemistry of halide-based solid electrolytes: unlocking advances in solid-state Li-ion batteries

Solid-state batteries (SSBs) represent a transformative advancement in electrochemical energy storage, offering exceptional energy density, enhanced safety, and broad operational temperature ranges, making them ideal for next-generation applications. While liquid electrolytes dominate conventional lithium-ion batteries (LIBs) due to their high conductivity and efficient electrode interface wetting, their flammability and volatility pose significant safety risks, particularly in electric vehicles and portable electronics. Solid electrolytes, a cornerstone of SSB technology, offer a promising pathway to enhance LIB energy density and safety. Among the various inorganic solid electrolytes, halide-based materials have garnered the main attention due to their remarkable ionic conductivity and robust mechanical properties. This review highlights recent advances in halide solid electrolyte design, synthesis, and electrochemical performance. Additionally, it discusses the challenges facing their integration into SSBs, an innovative technology poised to drive societal progress in sustainable energy solutions.