Emerging Superionic Sulfide and Halide Glass–Ceramic Solid Electrolytes: Recent Progress and Future Perspectives

Solid-state batteries (SSBs) are attracting attention as safe, high-energy and high-power-density electrochemical energy-storage systems. However, they are not yet capable of outperforming advanced lithium-ion batteries using liquid electrolytes. A critical obstacle relates to the development of cost-effective, inorganic solid electrolytes (SEs), combining superionic conductivity with high (electro)chemical stability and mechanical softness. Realizing intrinsically soft inorganic SEs is particularly challenging. Glass–ceramic SEs offer several advantages but typically exhibit low ionic conductivities. Given the recent developments of sulfide- and halide-based glass–ceramic materials, the overall objective of designing superionic (inorganic) SEs, entailing polymer- or clay-like softness, seems feasible. These SEs benefit from lower processing temperatures and versatile chemistries that allow for further enhancements. This Review provides a comprehensive overview of recent developments in the field of lithium glass–ceramic SEs and maps out factors governing conductivity and mechanical behavior. Finally, opportunities, challenges, and design principles for next-generation SEs are discussed.