Multifunctional Alternating Copolymer Nanoflower Iodine Hosts for Long-Term Zinc-Iodine Batteries

Aqueous Zn-iodine (Zn-I₂) 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-I₂ 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-I₂ battery. As a result, the NH-NFs-PDA/I₂-based Zn-I₂ 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.