Regulating the Electron Structure of Covalent Organic Frameworks to Enable Excellent Cycle Life and High Rate toward Advanced Zn−I₂ Batteries

Abstract

Abstract Aqueous Zn–iodine (Zn–I 2 ) batteries have attracted much attention due to their high theoretical capacity, high safety, and cost‐effectiveness. However, the poor electrical conductivity of iodine and shuttling of polyiodide limit the cycling life of Zn–I 2 batteries. Herein, a polyiodide host material constructed by a trifluoromethyl‐functionalized covalent organic framework (F‐COF) is set to regulate the electronic structure and stable polyiodide shuttle. Strong electron‐withdrawing trifluoromethyl groups can improve the electrostatic potential and boost adsorption performance. The theoretical results manifest that F‐COF has a high adsorption capacity for polyiodide to inhibit the shuttle effect. In situ Raman spectroscopy shows that I 3 − and I 5 − are the main form in the I − /I 2 conversion process. Therefore, the F‐COF loaded with iodine (F‐COF‐I 2 ) cathode achieves a specific capacity of 197 mAh g −1 at 1C and a Coulombic efficiency higher than 99.5%. In addition, it has a specific capacity of 112 mAh g −1 and can be stably cycled 40,000 times at 50C. Simultaneously, Zn corrosion can be restricted by F‐COF due to its polyiodide capture capacity. This work opens up a new avenue for the construction of polyiodide host materials with superior durability and electronic structure.