Recent Progress on Dominant Sulfide-Type Solid-State Na Superionic Conductors for Solid-State Sodium Batteries

Over the past decade, solid-state batteries have garnered significant attentions due to their potentials to deliver high energy density and excellent safety. Considering the abundant sodium (Na) resources in contrast to lithium (Li), the development of sodium-based batteries has become increasingly appealing. Sulfide-based superionic conductors are widely considered as promising solid eletcrolytes (SEs) in solid-state Na batteries due to the features of high ionic conductivity and cold-press densification. In recent years, tremendous efforts have been made to investigate sulfide-based Na-ion conductors on their synthesis, compositions, conductivity, and the feasibility in batteries. However, there are still several challenges to overcome for their practical applications in high performance solid-state Na batteries. This article provides a comprehensive update on the synthesis, structure, and properties of three dominant sulfide-based Na-ion conductors (Na₃PS₄, Na₃SbS₄, and Na₁₁Sn₂PS₁₂), and their families that have a variety of anion and cation doping. Additionally, the interface stability of these sulfide electrolytes toward the anode is reviewed, as well as the electrochemical performance of solid-state Na batteries based on different types of cathode materials (metal sulfides, oxides, and organics). Finally, the perspective and outlook for the development and practical utilization of sulfide-based SE in solid-state batteries are discussed.