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

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.