Dual‐Electrode Synergistic Electrolyte Enabling Highly Reversible Multi‐Electron Redox in Aqueous Zinc‐Iodine Batteries

Abstract Multi‐electron redox strategies offer promising approaches to achieve high energy density in aqueous Zn‐iodine (Zn─I 2 ) batteries, yet the development is impeded by unstable intermediate species, slow redox kinetics, and poor reversibility, particularly at low current densities. Herein, 1‐pentyl‐3‐methylimidazolium bromide ([PeMIM] + Br − ) is employed to develop a dual‐electrode synergistic electrolyte (DESA‐E), which enables the multi‐electron conversion of Zn─I 2 batteries with high specific capacity and long‐term cycling stability. The Br − in DESA‐E induces dual‐halogen synergy, accelerating cascade I − /I 0 /I + four‐electron conversion kinetics and activating the Br − /Br 0 redox reactions for ultra‐high specific capacity. Meanwhile, hydrophobic [PeMIM] + alkyl chains stabilize interhalogen intermediates, suppress I + hydrolysis, and guide Zn deposition along the (002) plane via electrostatic effect. Consequently, the DESA‐E enables Zn─I 2 batteries with a specific capacity of 557 mA h g −1 after 500 cycles at 0.5 A g −1 with an average coulombic efficiency of 99.97%, and maintains a low degradation rate of 0.00055% per cycle over 60 000 cycles at 8 A g −1 . This work presents a facile and cost‐effective electrolyte design to enable durable multi‐electron Zn─I 2 batteries for high‐energy‐density systems.