A PF6−‐Permselective Polymer Electrolyte with Anion Solvation Regulation Enabling Long‐Cycle Dual‐Ion Battery

Abstract Graphitic carbon that allows reversible anion (de)intercalation is a promising cathode material for cost‐efficient and high‐voltage dual‐ion batteries (DIBs). However, one notorious but overlooked issue is the incomplete interfacial anion desolvation, which not only reduces the oxidative stability of electrolytes, but also results in solvent co‐intercalation into graphite layers. Here, an “anion‐permselective” polymer electrolyte with abundant cationic quaternary ammonium motif is developed to weaken the PF 6 − –solvent interaction and thus facilitates PF 6 − desolvation. This strategy significantly inhibits solvent co‐intercalation as well as enhances the oxidation resistance of electrolyte, ensuring the structural integrity of graphite. As a result, the as‐assembled graphite||Li cell achieves a superior cyclability with an average Coulombic efficiency of 99.0% (vs 95.7% for baseline electrolyte) and 87.1% capacity retention after 2000 cycles even at a high cutoff potential of 5.4 V versus Li + /Li. Besides, this polymer also forms a robust cathode electrolyte interface, working together to enable a long‐life DIB. This strategy of tuning anion coordination environment provides a promising solution to regulate solvent co‐intercalation chemistry for DIBs.