Abstract: Extensive research into solid-state electrolytes during the last half-century has led to the discovery of a number of solids showing a high ionic conductivity at room temperature. The use of a solid-state electrolyte can enable solid-state battery to achieve high performance such as high energy density, large temperature operation window, fast charging capability, long cycling life, and excellent safety.

In this talk, I will present our recent work on development of a solid-state electrolyte and cell components for solid-state batteries including a solid-state sodium-ion battery and solid-state lithium-sulfur batteries. We have developed a series of ternary and quaternary glass-ceramic thiophosphate sodium-ion conductors such as Na₃P_1-xAs_xS₄, Na₁₁Sn₂PS₁₂, and Na₁₁Sn₂PSe₁₂. I will present our understanding of the origin of the exceptional conductivity via anion/cation substitution and a new crystalline phase for quaternary thiophosphate with increased sodium vacancies and three-dimensional sodium-ion conduction pathways for improved conductivity. I will also present our recent progress in developing a new carbon-sulfur composite, asolid-state electrolyte, and additives to address technological challenges of solid-state lithium-sulfur batteries, such as low sulfur utilization and increased interfacial resistances due to poor contact and the unoptimized microstructure of sulfur-carbon-SSE composites in the solid cathode.