Synergistic Poly(Ionic Liquid)-CMC binder with ionic liquid electrolytes for high-performance, polysulfide-free lithium-sulfur batteries

Lithium–sulfur (Li-S) batteries are among the most promising next-generation energy storage technologies due to their high theoretical energy density and the abundance of sulfur. However, their practical implementation is limited by active material loss, unstable electrode interfaces, intermediate polysulfide dissolution, and low sulfur utilization. In this study, we present a hybrid binder composed of a lithium-ion-conductive poly(ionic liquid) (PIL), poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDADMA-TFSI), and carboxymethyl cellulose (CMC) engineered to operate synergistically with ionic liquid (IL) electrolytes based on trimethylisobutylphosphonium bis(fluorosulfonyl)imide [P 111i4 ][FSI] and N-trimethyl-N-propylammonium bis(fluorosulfonyl)imide [N 1113 ][FSI]. This PIL-CMC binder significantly improves interfacial stability and enables efficient sulfur utilization in polysulfide-free cycling. Among all combinations tested, 50 mol% LiTFSI in [N 1113 ][FSI] exhibited the best electrochemical performance, sustaining capacities above 1100 mA h g −1 for over 100 cycles at 50 °C. A reduced total binder content formulation (5 wt% PIL and 5 wt% CMC) maintained comparable performance, suggesting potential for further optimization. Electrochemical analysis revealed low voltage polarization and high Coulombic efficiency of up to 99.5 %, while UV–vis and Raman spectroscopy confirmed the absence of dissolved polysulfides. Overall, this work demonstrates a robust and scalable strategy for realizing additive-free, thermally stable Li-S cathodes, emphasizing the importance of binder–electrolyte integration in the design of high-performance Li-S batteries. • Poly(ionic liquid)–CMC binder enhances sulfur utilization and cycling stability. • Mixed binder promotes ionic conductivity and mechanical integrity synergy. • Ionic liquid electrolytes suppress polysulfide dissolution for stable cycling. • Ammonium-based IL electrolyte improves lithium-ion transport and SEI stability. • Cells retain capacities >1100 mAh g −1 over 100 cycles at 50 °C.