Challenges and prospects for room temperature solid-state sodium-sulfur batteries

Room temperature sodium-sulfur (Na-S) batteries, known for their high energy density and low cost, are one of the most promising next-generation energy storage systems. However, the polysulfide shuttling and uncontrollable Na dendrite growth as well as safety issues caused by the use of organic liquid electrolytes in Na-S cells, have severely hindered their commercialization. Solid-state electrolytes instead of liquid electrolytes are considered to be the most direct and effective solution to solve the above problems. However, its practical application is still greatly challenged due to the poor interfacial compatibility between the all-solid-state electrolytes and the anode/cathode, ionic conductivity, and the shuttle effect caused by the presence of liquid phase in the quasi-solid-state electrolytes. This paper presents a comprehensive review of solid-state Na-S batteries from the perspective of regulating interfacial compatibility and improving ionic conductivity as well as suppressing polysulfide shuttle. According to different components, solid-state electrolytes were divided into five categories: solid inorganic electrolytes, solid polymer electrolytes, polymer/inorganic solid hybrid electrolytes, gel polymer electrolytes, and liquid–solid inorganic hybrid electrolytes. Finally, the prospect of developing high performance solid-state electrolytes to improve the cycling stability of room temperature Na-S cells is envisaged.