A Coupled Electrolyte Design to Reconcile Multielectron Iodine Redox With Zn Anode Reversibility for Durable Aqueous Zinc‐Iodine Batteries

ABSTRACT Aqueous Zn||I 2 batteries provide advantages in terms of safe operation and economical energy storage, yet their practical deployment is markedly constrained by the insufficient capacity of conventional two‐electron iodine redox chemistry and the unfavorable interfacial reactions at the Zn surface. Herein, a coupled electrolyte regulation strategy is reported that incorporates choline chloride (ChCl) and acrylamide (AM) into the ZnSO 4 electrolyte, enabling comprehensive regulation from the anode to the cathode. This design not only facilitates reversible high‐valence iodine chemistry via the formation of stable ICl intermediates but also induces in situ generation of a distinctive PAM‐Ch + solid electrolyte interphase (SEI) on the Zn surface. As a result, durable multielectron iodine redox chemistry is realized in aqueous Zn||I 2 cells while preserving high Zn anode reversibility. The Zn anode operates stably for over 5000 h at room temperature, while the Zn||I 2 full cell delivers a specific capacity of 340.83 mAh g −1 at 1 A g −1 and retains 81.2% of the capacity after 6000 cycles at 5 A g −1 . This work offers a strategy to reconcile multielectron iodine conversion with Zn anode interphase stability, providing guidance for high‐energy‐density aqueous battery design.