A thermally stable and shuttle-effect-resistant iodine cathode for aqueous zinc metal batteries

Aqueous Zinc-Iodine (Zn-I₂) batteries are regarded as a promising candidate for stationary energy storage, owing to their advantages in cost, safety, and environmental sustainability. However, the practical deployment of such batteries is hindered by the instability of the iodine cathode. Specifically, iodine's low thermal stability complicates electrode fabrication, while soluble polyiodide species induce a shuttle effect that lowers Coulombic efficiency and accelerates capacity fading. To address these issues, this work develops an iodine cathode based on metal organic framework (MOFsingle bondI2) cathode. The Zeolitic Imidazolate Framework-8 (ZIF-8) host exhibits strong adsorption capability toward iodine and polyiodides, thereby enhancing both thermal stability and shuttle resistance. The nature of the interaction between ZIF-8 and iodine/polyiodides is systematically investigated through a combination of X-ray total scattering, spectroscopic methods and density functional theory (DFT) calculations. It is shown that the resulting I₂@ZIF-8 composite can be processed at temperatures up to 120 °C without significant iodine sublimation, which is compatible with common electrode manufacturing conditions. ... mehrMoreover, the shuttle effect is substantially suppressed, as predicted by DFT and experimentally verified. As a result, the I₂@ZIF-8 cathode enables Zn-I₂ full cells to deliver highly reversible capacity and significantly improved long-term cycling stability, demonstrating a viable pathway toward more robust aqueous iodine-based batteries.