Spatially Decoupled Sulfur Redox and Li⁺ Transport in Polymer Electrolytes for Solid-State Li-S Batteries.

Abstract

In poly(ethylene oxide) (PEO)-based solid-state Li-S batteries (SSLSBs), the stepwise sulfur redox reaction enables smooth energy delivery. However, concentrated polysulfides severely hinder Li⁺ transport and induce rapid performance degradation during cycling. Herein, we report a spatially decoupling strategy for sulfur redox and Li⁺ transport by introducing poly(vinylidene fluoride) (PVDF) into the PEO matrix. Due to the intrinsic low affinity of PVDF toward sulfur species, polysulfides dissolution is effectively suppressed within the PVDF phase, enabling continuous Li⁺ transport when the PEO phase is clogged by accumulated polysulfides. By regulation of phase separation and Li⁺ coordination in the PEO-PVDF hybrid, a Li⁺ conductive network is established within the PVDF phase, while the PEO phase preserves stepwise sulfur redox. As a result, the SSLSBs deliver a high initial capacity of 1402 mAh g^-1 at 0.08 C. Even at 0.2 C, a stable capacity of ∼560 mAh g^-1 is maintained over 90 cycles.