Ca²⁺-Preintercalated V₂O₅ as a Dual-Function Cathode Additive for Polyiodide Anchoring in Zn–I₂ Batteries

Aqueous zinc–iodine (Zn–I 2 ) batteries have attracted considerable attention due to their abundant resources, high safety, and environmental friendliness. However, challenges inherent to conversion-type electrodes, including severe active material shuttling and suboptimal Coulombic efficiency, continue to limit their performance. Here, we present a high-performance Zn–I 2 battery enabled by calcium-ion-preintercalated V 2 O 5 (CaVO) nanobelts as a cathode additive. By harnessing the synergistic effects of physical trapping (via activated carbon and interlayer confinement in CaVO) and chemical adsorption (through Ca 2+ binding sites), the hybrid host framework achieves superior immobilization of iodine species while simultaneously shortening Zn 2+ diffusion pathways, thereby facilitating efficient I 0 /I – redox kinetics. Furthermore, Ca-induced crystal structure modification enhances the Zn 2+ transport and provides additional capacity contributions. As a result, Zn–I 2 cells employing I 2 -loaded CaVO (CaVO/AC@I 2 ) composite cathodes deliver a high specific capacity of 244 mAh g –1 at 0.2 A g –1, outstanding rate performance with 78.5% capacity retention at 5 A g –1, and an impressive energy density of 279 Wh kg –1, based on the combined mass of I 2 and CaVO. This work presents a hybrid energy storage strategy for Zn–I 2 systems, providing a feasible approach for the development of next-generation high-performance aqueous batteries.