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

A series of R-SO₃H-containing polyimides are synthesized as binders for iodine-loading cathode. Profiting from structural merits, PI-4S binder with R-SO₃H, hydroxyl and imide groups hold stronger chemisorption capability for iodine species (I₂/I⁻/I₃ ⁻) to suppress the active I₂ dissolution and polyiodide shuttle behavior, which effectively reduces corrosion of zinc negative electrodes in 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.