A review on design of cathode, anode and solid electrolyte for true all-solid-state lithium sulfur batteries

All-solid-state lithium sulfur batteries (ASSLSBs) are a promising prospect in the field of energy storage devices offering high energy density and safety. An ASSLSB is realized by replacing the liquid electrolyte in conventional lithium-sulfur batteries (Li–S batteries) by solid-state electrolytes (SSEs). This review acknowledges the practical challenges that makes the actual performance of ASSLSB fall behind the conventional counterparts. The discussion is restricted to true ASSLSBs devoid of liquid components, unlike gel polymer electrolytes, quasi-solid-state electrolytes or electrode/SSE interface wetting. The insulating nature of sulfur and its discharge products makes the sluggish reaction kinetics in the solid-state even slow. The build-up of electrochemically dead materials at the cathode hinders fresh sulfur surface from partaking in reaction, thereby drastically reducing the sulfur utilization. Therefore, an optimized cathode structure with a dual ionic and electronic conduction pathway is required. Also, the polysulfides generated at cathode in ASSLSBs can dissolve in polymer-based SSEs used and unevenly passivate the lithium metal anode. Based on this understanding, the review focuses on modifications of sulfur cathode and design of protective interlayer to restrict (chain) polysulfide dissolution, limit (cage) polysulfide migration to the lithium anode and the protection of lithium anode from polysulfide attack (shield) in ASSLSBs.