Fluorine Modified Zeolitic Imidazolate Framework Enables Long-Life Zn-I Batteries by Suppression of Polyiodide Shuttle.

Aqueous zinc-iodine (Zn-I) batteries have emerged as a promising candidate for large-scale energy storage applications, owing to their inherent safety, cost-effectiveness, and high specific capacity. However, their commercial implementation is severely hindered by the irreversible capacity degradation and limited cycle life, which are caused by the unavoidable iodine shuttle effect resulting from the formation of soluble I species. Herein, we report the synthesis of three-dimensional hexapod-like fluorine-containing zeolitic imidazolate framework (H-F-ZIF) nanoparticles for separator modification to effectively inhibit the iodine shuttle effect. The modified layer can interact with the I species at the cathode-separator interface where the iodine shuttle occurs. Furthermore, the fluorine-containing functional group (─CF) serves as an electron acceptor, enhancing the electrostatic interaction with I species, and thereby improving the polyiodide capture capacity. As a result, the Zn-I battery using H-F-ZIF modified separator exhibits excellent cycling durability and high capacity, retaining a capacity of 155.7 mAh g after 12 000 cycles at 1.2 A g, and a coulombic efficiency of 86.4% after 48 h of resting.