Functionally Segregated Ion Regulation Enables Dual Confinement Effect for Highly Stable Zinc-Iodine Batteries

Conventional electrolytes in aqueous zinc-iodine batteries struggle to suppress the shuttle effect and enhance interfacial stability, resulting in high self-discharge rate, low areal capacity, and short cycle life. To address these issues, a dual-confinement hydrogel electrolyte (DCHE) is designed to simultaneously stabilize the iodine cathode and zinc anode at high areal capacities via a functionally segregated ion regulation strategy. As for the cathode, anion-functional groups in the DCHE repel polyiodides, while cation-functional groups adsorb those that escape repulsion, thereby reinforcing the suppression of polyiodide migration toward the zinc anode. This dual confinement effect, validated by theoretical simulations and in situ characterization, effectively mitigates the shuttle effect. Additionally, hydrophilic and zincophilic functional groups regulate the hydrogen-bond network and Zn²⁺ flux, strengthening the electrochemical stability of the zinc anode. As a result, a Zn//ZnI₂ cell assembled with DCHE delivers a practical areal capacity of 4.5 mAh cm^-2 and achieves a record-long lifespan exceeding 6000 h with 88.9% capacity retention at 100 mA g^-1. Furthermore, the single-layer pouch cell exhibits good mechanical stability, retaining 80% of its capacity after 100 cycles of 90° bending. This work highlights the importance of functionally segregated ion regulation in advancing high-performance aqueous batteries.