Vanadium-Based Prussian blue analogue for high energy aqueous Zinc-Iodine batteries

Aqueous zinc-iodine (Zn-I) batteries typically suffer from poor Coulombic efficiency and limited cycling performance, primarily due to the shuttle effect caused by soluble iodine-based species. Developing novel iodinehosting materials with effective physical and chemical confinement capabilities for iodine species represents a promising strategy to address these challenges. Herein, we introduce a vanadium-based Prussian blue analogue (V-PBA) as a cathodic material for aqueous Zn-I batteries with multielectron transfer for the first time. A highly concentrated hybrid electrolyte system (11 M ZnCl2 + 0.35 M ZnI2) enables the I-/I3-/I+ redox processes. Spectroscopic analyses and theoretical simulations reveal that the vanadium sites on the outer surface of V-PBA exhibit strong interactions with various iodine-based species, including I-, I2, I3-, and I+. These interactions induce charge redistribution between the iodine species and the vanadium sites in V-PBA, enhancing the d-band center of vanadium and increasing the metallic character of the adsorbed iodine species. This synergy effectively suppresses the shuttle effect and accelerates the reaction kinetics of the complex iodine conversion reactions, resulting in high iodine utilization, improved Coulombic efficiency, and enhanced cycling performance. Overall, the comprehensive performance of this system ranks among the best for state-of-the-art Zn-I batteries.