A poly(sodium 4-styrenesulfonate)-MXene composite as an ultrathin separator coating for high-performance...

Lithium‑sulfur (LiS) batteries are regarded as compelling candidates for next-generation energy storage systems, leveraging their exceptional theoretical energy density and the high natural abundance of elemental sulfur. Nevertheless, their commercialization faces significant obstacles, such as polysulfide shuttling, sluggish reaction kinetics, and the growth of lithium dendrites. Herein, a poly(sodium 4-styrenesulfonate)-MXene (PSSMX) composite is designed and fabricated as an ultralight and ultrathin multifunctional separator coating to address these issues concurrently. Combined theoretical and experimental investigations reveal that the PSSMX layer, enriched with sulfonate groups, functions dually by electrostatically repelling polysulfide anions and chemically binding lithium polysulfides, thereby effectively inhibiting their shuttling. Furthermore, it facilitates Li⁺ transport, promotes Li⁺ desolvation, and enhances the deposition kinetics of Li₂S, thereby stabilizing the lithium negative electrode. Consequently, a LiS cell incorporating the PSSMX-modified separator delivers a remarkable specific capacity of 661.7 mAh g^-1 at 4.0C and sustains stable operation over 300 cycles at 0.2C with a minimal capacity fade rate of 0.08% per cycle. Even under the demanding conditions of high sulfur loading and low electrolyte dosage, the cell exhibits an impressive initial specific capacity of 1127.5 mAh g^-1 at 0.1C.