Competitive anion coordination overcomes charge-transfer barriers for lithium–sulfur batteries

Beyond ionic conduction and solid-electrolyte interphase formation, the fundamental roles of lithium salt anions in batteries remain unexplored. Herein, an anion-induced competitive solvation mechanism that governs lithium polysulfide (LiPS) behaviors in high-energy-density lithium–sulfur batteries is pioneeringly unveiled. Specifically, anions contend against weakly solvating solvents to occupy the LiPS inner solvation shell. Enhancing anion coordination while diminishing weakly solvating solvent coordination overcomes the rate-determining LiPS charge-transfer barriers. As a proof of concept, bis(fluorosulfonyl)imide anion coordination reduces activation polarization and boosts cycling stability at high current densities. Ah-level pouch cells achieve stable operation at high rates of 0.35 C and deliver a record-setting energy density of 622 Wh kg⁻¹ (based on total weight) with stable cycling. By elucidating the anion-induced competitive solvation mechanism, our work transcends conventional views of anion roles and establishes a new paradigm for advancing practical Li–S batteries.