Mitigating Cathodic Challenges in Aqueous Zn– I 2 Batteries via Dual‐Effect Function Strategy: Concurrent I 3 − Immobilization and Catalysis of I 0 /I − Redox Kinetics

Aqueous‐based zinc‐iodine batteries (AZIBs) are extremely competitive and have gigantic potential in the next generation of energy storage technologies on account of their ultra‐high safety and excellent theoretical capacity. Howbeit, the unsatisfactory conductivity of iodine and the shuttle effect of polyiodides will greatly confine their commercial applications. In this study, an original composite material of selenium (Se) and activated carbon (AC) (designated as Se–AC), as a functional iodine‐adsorbed cathode host, is successfully synthesized with the dual‐effect function of Se. Se has a larger atomic size and higher polarizability compared to carbon, effectively accelerating the charge transfer rate. Therefore, the incorporation of Se nanoparticles can generate higher strain at the edge of AC to improve the adsorption of iodine species, especially I 3 − . Furthermore, the inorganic Se nanoparticles can make AC provide abundant adsorption‐catalytic active sites that significantly enhance electron transfer kinetics while catalyzing the I 0 /I − conversion reaction. As expected, Se–AC/I 2 can deliver an ideal specific capacity of 249.7 mAh g −1 at 0.1 A g −1 . Additionally, the energy density of Se–AC/I 2 //Zn exhibits 217.5 Wh kg −1 at 86.2 W kg −1 , exceeding most reported AZIBs. This dual‐effect function strategy creates transformative opportunities for AZIBs, enabling high energy density, long cycling, and cost‐effective energy storage solutions for renewable grids.