Cation-anion synergistic dual-interface regulation by In(OTf)3 additive enabling ultralong-life lithium-sulfur batteries

Journal article, 2026

The polysulfide shuttle and lithium dendrite growth remain two intertwined bottlenecks that degrade the practical viability of lithium-sulfur (Li-S) batteries. Herein, a cation-anion synergistic dual-interface engineering strategy is reported by employing indium trifluoromethanesulfonate (In(OTf)3) as a bifunctional electrolyte additive. On the sulfur cathode, Lewis-acidic In³⁺ cations strongly immobilize soluble lithium polysulfides through In–S coordination and catalyze their bidirectional redox conversion, while an in-situ formed gradient cathode-electrolyte interphase enriched with In2S3 and LiF physically and chemically confines sulfur species and facilitates interfacial charge transfer. On the lithium anode, electrochemically reduced indium species cooperate with OTf⁻ anions to generate a homogeneous Li-In alloy/LiF composite solid-electrolyte interphase that homogenizes Li⁺ flux, reduces nucleation overpotential, and suppresses dendrite proliferation. This synergistic cathode-anode regulation drastically lowers interfacial polarization and accelerates Li2S precipitation/decomposition kinetics, as confirmed by in-situ spectroscopy and electrochemical analyses. Consequently, the optimized Li-S cell delivers an ultralow capacity decay of 0.048% per cycle over 1000 cycles at 2 C, a high-rate capability of 872 mAh g⁻¹ at 3 C, and an exceptional lifespan exceeding 3100 h in symmetric cells. A high-sulfur-loading pouch cell (5.67 mg cm⁻²) further achieves stable cycling under lean-electrolyte and mechanical deformation conditions. This work elucidates the cation-anion synergistic interfacial chemistry of indium-based additives and presents a scalable electrolyte engineering strategy for high-energy-density Li-S batteries.