Customized Design of R-SO3H-Containing Binders for Durable Iodine-Loading Cathode of Zinc–Iodine Batteries

Abstract

The challenges of iodine dissolution and polyiodide shuttle behavior severely hinder the development of zinc–iodine batteries (ZIBs). Among the battery components, binders play a vital role in maintaining mechanical integrity and facilitating the iodine conversion reaction of the iodine-loading cathode in ZIBs. Herein, a series of polyimide-based polymers rich in the sulfonic acid group (R-SO₃H) are elaborately designed as functional binders for iodine-loading cathodes. According to the spectroscopic characterization and theoretical calculation results, PI-4S binder with R-SO₃H, hydroxyl and imide groups holds stronger chemisorption capability for I₂/I⁻/I₃⁻ species, which effectively helps to block the polyiodide shuttle and the active iodine's dissolution behavior. As a result, the corresponding ZIBs with PI-4S as binders deliver a reversible capacity of 142.7 mAh g⁻¹ over 600 cycles at 0.2 A g⁻¹, a high capacity of 157.6 mAh g⁻¹ over 500 cycles at 0.5 A g⁻¹ at 50 °C, and durable cycling stability of 88 mAh g⁻¹ over 15000 cycles at 4 A g⁻¹. This work guides the autonomous design of multifunctional polymer binders for iodine-loading cathodes and facilitates the practical application of ZIBs.