Suppressing argyrodite oxidation by tuning the host structure for high-areal-capacity all-solid-state lithium–sulfur batteries

Argyrodite (Li₆PS₅Cl) is a promising electrolyte for high-performance solid-state lithium-sulfur batteries (SSSBs), which operate on the reversible conversion of S↔Li₂S. However, argyrodite is electrochemically decomposed above 2.5 V versus Li⁺/Li on charge, because free S^2- ions in the lattice are oxidized to sulfur at a similar potential as Li₂S. Here we demonstrate that creating a strong interaction between the Li ions in argyrodite and the sulfur host synergistically suppresses the oxidation of argyrodite by inhibiting the extraction of Li⁺ in the initial step. A carbon nitride/N-doped graphene host serves as a proof of concept to demonstrate this effect. Additionally, its moderate electron transport enables SSSB operation and constrains electron mobility at the argyrodite interface. Consequently, SSSBs utilizing this host deliver excellent rate capability and stable long-term cycling compared with non-polar carbon materials. An areal capacity of 2 mAh cm^-2 was achieved over 230 cycles at room temperature, whereas a high capacity of 11.3 mAh cm^-2 was obtained with 90% retention at 60 °C. The descriptors presented here could enrich the understanding of solid electrolyte redox activities and guide interface and materials design in SSSBs.