Synergistic Strategy of Targeted Capture and Potential Responsive Release for High-Performance Zinc-Iodine Batteries.

Abstract

The shuttle effect, arising from the dissolution and migration of polyiodide species, severely hinders the practical application of high-energy-density zinc-iodine (Zn─I₂) batteries. Conventional carbon-based cathode materials, relying on weak physical adsorption, fail to effectively confine iodine species. To address this issue, a synergistic strategy is proposed that combines the targeted capture of I^- to form BiOI with the potential responsive release of I^- from BiOI during the reduction of Bi³⁺ to Bi. This approach enables a dynamic and directional capture-release process at a potential lower than that required for the reduction of I₂. This methodology is validated through ex situ spectroscopic analysis and Density functional theory (DFT) calculations. This decoupled mechanism suppresses polyiodide formation and ensures efficient cathode reversibility. The incorporation of Bi₂O₃ also introduces an additional redox couple, contributing extra capacity to the battery. The battery not only efficiently suppresses the inherent side reaction issues of zinc-iodine batteries, but also achieves a considerably high capacity level in the field of iodine single-electron conversion. This work provides a universal design principle for manipulating iodine electrochemistry, paving the way for high-energy, long-lifespan halogen-based batteries.