Engineering Bifunctional Carbon Hosts with Rich ─OH and ─C═O for Synergistic Confinement and Redox Kinetics in Zn‐I ₂ Batteries

ABSTRACT Aqueous zinc‐iodine (Zn‐I 2 ) batteries have attracted extensive attention as next‐generation energy storage systems due to their inherent safety, environmental benignity, and theoretical high capacity (211 mAh g −1 ). Nevertheless, their practical application is still hampered by the dissolution and shuttling of soluble polyiodides, leading to rapid capacity decay and inferior cycling stability. Although porous carbon‐based host materials physically confine iodine species, thereby improving electrochemical performance, the crucial role of surface functional groups on carbon (─OH, ─C═O, and ─COOH) in regulating the electrochemical behavior has been neglected. Herein, we designed and synthesized hierarchical micro‐mesoporous carbon (MMC) nanospheres rich with hydroxyl (─OH) and carbonyl (─C═O) groups as iodine hosts. The multiscale porous structure facilitates high iodine loading, while ─OH groups remarkably enhance the chemical adsorption of iodine species via O─H∙∙∙I bond, thereby suppress the shuttle effect. Additionally, ─C═O groups actively participate in additional Faradaic redox reactions. Consequently, the prepared I 2 /MMC‐Rich electrode delivers outstanding electrochemical performance: it provides an initial capacity of 160.87 mAh g −1 at 10 A g −1 and maintains 135.58 mAh g −1 after 25 000 cycles, with a capacity retention rate of 84%. This work offers a rational strategy for developing functional carbon materials toward high‐performance and long‐life Zn‐I 2 batteries.