pH‐Responsive Ion Gating for Durable Aqueous Zinc–Iodine Batteries

Aqueous zinc‐iodine (Zn‐I 2 ) batteries have emerged as promising candidates for long‐duration energy storage, benefiting from their inherent safety and low cost. However, their practical implementation is hindered by limited cycling stability, primarily caused by polyiodide shuttling and inhomogeneous Zn 2+ flux. Herein, we design a dynamic polymer brush modified separator featuring a pH‐responsive ion‐gating function for bidirectional ion regulation, which is fabricated by grafting polyethyleneimine onto a bacterial cellulose matrix. The brush reversibly adjusts its protonation state and conformation in response to local pH variation, selectively regulating Zn 2+ transport to guide dendrite‐free, (002)‐textured Zn deposition. Simultaneously, the positively charged sites in the brush effectively capture polyiodides during discharge and release them under an electric field upon charging, thereby suppressing the shuttle effect. As a result, the developed separator enables highly stable Zn deposition–stripping over 2300 h at 10 mA cm − 2 and 10 mAh cm − 2 and endows Zn‐I 2 batteries with a cycle life exceeding 64,000 cycles. This work demonstrates a feasible bidirectional ion‐regulation strategy to achieve uniform Zn deposition and inhibit polyiodide shuttling, providing a promising path toward practical and durable aqueous Zn‐I 2 batteries.