Innovative Ionic Liquid Electrolyte: Dual Proton Sources and K⁺ Synergistic Transport Enhanced Proton Battery Performance

Abstract This study puts forward an innovative electrolyte design to resolve the problems of scarce efficient proton sources and interface instability in proton batteries. It verifies that hydrogen protons mainly come from water molecule dissociation, with acetic acid acting as an auxiliary source, leading to proton source concentration changes during charging/discharging. To address this, an ionic liquid (1‐Ethyl‐3‐methylimidazolium acetate, abbreviated as [emim][Ac]) electrolyte containing acetic acid (HAc) and potassium acetate (KAc) ([emim][Ac] + 4 m HAc + 1 m KAc) is developed. Experimental results show the battery performs excellently, with a discharge capacity up to 1584 mAh g ⁻¹ , and retains 1217 mAh g ⁻¹ at a 6000 mA g ⁻¹ discharge current density after 300 cycles. Both experiments and simulations confirm H⁺ primarily comes from HAc and H ₂ O solvated by K⁺ and imidazolium cations. K⁺ introduces a new “vehicle transport channel” to reduce proton transport resistance, while HAc and KAc form a buffer solution to optimize solvation structure and inhibit side reactions. Ionic liquids provide a stable environment for ion transport. This work offers references for developing high‐rate, long‐cycle proton batteries.