Taming polyiodides: Phenol chemistry for shuttle-free and durable zinc-iodine batteries

Abstract

Zinc-iodine (Zn-I2) batteries have emerged as promising candidates for large-scale energy storage, but the practical application is still significantly hindered by the notorious polyiodide shuttle effect, which always results in active iodine loss, severe zinc corrosion, and irreversible capacity attenuation. Herein, resorcinol (RSC), constructed by benzene ring and phenolic hydroxyl groups, is verified as an effective electrolyte additive to simultaneously stabilize the iodine-loading cathode and zinc anode of Zn-I2 batteries. Theoretical calculations demonstrate RSC molecules hold more negative adsorption energies for polyiodides and lower Gibbs free energies for iodine reduction process, manifesting strong chemisorption capability for polyiodides and strengthened iodine conversion kinetics. Consequently, Zn||AC@I2 batteries in RSC-containing electrolyte deliver high reversible capacity of 141.1 mA h g-1 and high retention rate of 85.8% after 10000 cycles at 1 A g-1. Even after 17000 cycles at 5 A g-1, the reversible capacity stabilizes at 106.2 mA h g-1 with high retention rate of 90.1%. The corresponding pouch batteries with high iodine loading of 12.7 mg cm-2 present high capacity of 165.8 mA h g-1 and high retention rate of 97.9% after 200 cycles at 0.5 A g-1. This work provides a cost-effective strategy to inhibit polyiodide shuttle behavior, and ensure durable cyclic stability of Zn-I2 batteries.