Confining Polyiodide in Polymer Cathode Boosts Cycling Stability in High Energy‐Dense Aqueous Zinc‐Sulfur Batteries

ABSTRACT Aqueous zinc‐sulfur (Zn/S) batteries are emerging as sustainable energy storage systems owing to their high theoretical capacity, environmental safety, and cost‐effectiveness. However, their practical application is hindered by sluggish solid‐solid sulfur conversion kinetics and the persistent need for soluble iodine redox mediators that exacerbate zinc anode corrosion and dendrite formation. Here, we report an integrated polymer–polyiodide confinement strategy employing a cationic poly(vinyl butyl imidazolium iodide) framework ([PVIM]I) complexed with iodine to form a redox‐active polymer‐polyiodide framework ([PVIM]I x ). The polymer matrix spatially confines polyiodide species, minimizing their crossover and suppressing zinc anode corrosion while enhancing sulfur redox kinetics. The resulting metal‐free and binder‐free ([PVIM]I x ) cathode delivers a high specific capacity of 1845 mAh g −1 (1548 mAh g −1 excluding iodine contribution) at 0.1 A g −1 with an energy density of 923 Wh kg −1 , maintaining excellent cycling stability with 93.7% capacity retention over 500 cycles at 5 A g −1 . Improved ion diffusion and reduced polarization were confirmed by GITT and in situ impedance spectroscopy. This polymer‐iodide composite provides a scalable and stable platform for advancing aqueous Zn/S batteries, addressing key challenges in cathode wettability and redox mediation to enable sustainable, high‐performance energy storage solutions.