Spatially engineered polymer-in-salt electrolytes for solid-state lithium-sulfur batteries

Solid-state electrolytes (SSEs) suppress polysulfide shuttling in lithium–sulfur (Lisingle bondS) batteries yet introduce intrinsic barriers by slowing solid-state sulfur conversion. Here, we introduce an asymmetric, region-specific polymer-in-salt (PIS) electrolyte architecture that addresses these coupled limitations. The poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) PIS matrix suppresses polysulfide crossover and provides an ionic conductivity of 5.3 × 10-4 S cm-1; a polyethylene oxide (PEO)–rich cathode interface enables stepwise sulfur conversion mediated by lithium polysulfides; and a lithium aluminum titanium phosphate (LATP)–reinforced anode-side electrolyte increases the Li+ transference number to 0.59 while maintaining stable Li-metal cycling for more than 350 h. Lisingle bondS cells using this architecture deliver an initial capacity of 1180 mAh g-1 at 0.05C (1 mg S cm-2) and retain 78% of their capacity after 120 cycles at 0.2C. At a sulfur loading of 2.7 mg cm-2 and an N/P ratio of 4.5, the cells retain 80% of their capacity over 50 cycles. These results demonstrate that spatially decoupling electrolyte functions at the cathode, bulk, and anode interfaces provides a scalable and mechanistically grounded design principle for improved solid-state Lisingle bondS batteries.