Multifunctional Alternating Copolymer Nanoflower Iodine Hosts for Long‐Term Zinc–Iodine Batteries

Abstract Aqueous Zn–iodine (Zn‐I 2 ) batteries are considered to be potential energy storage systems due to their safety, environmental friendliness, and cost‐effectiveness. However, the shuttle effect of polyiodide leads to cathode active mass loss and anode Zn corrosion, which greatly reduces the cycle life of Zn‐I 2 batteries. Herein, we report an N ‐modified alternating copolymer nanoflower composite (NH‐NFs‐PDA) as a new type of iodine host candidate to effectively inhibit the polyiodide shuttle effect in Zn‐I 2 battery. As a result, the NH‐NFs‐PDA/I 2 ‐based Zn‐I 2 battery demonstrates a high specific capacity of 185.42 mAh g −1 at 1 A g −1 , with a coulombic efficiency of 99%. Moreover, it exhibits excellent cycling stability, achieving 10,000 cycles at 10 A g −1 with an average capacity decay rate of only 0.0008% per cycle, ranking it among the best‐performing polymeric host‐based Zn‐I₂ batteries in the literature. Density functional theory (DFT) and in‐ situ ultraviolet‐visible (UV‐Vis) measurements illustrate the impressive suppression of polyiodide shuttle effect comes from the strong interaction between N ‐modification enhanced polyhydroxy sites in NH‐NFs‐PDA and polyiodide. This work may shed new light on the design of advanced polymeric iodine hosts in Zn‐I₂ batteries.