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 their 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), comprising a 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 demonstrated that RSC molecules exhibit more negative adsorption energies for polyiodides and lower Gibbs free energies for the iodine reduction process, manifesting strong chemisorption capability for polyiodides and strengthened iodine conversion kinetics. Consequently, Zn‖AC@I₂ batteries using an RSC-containing electrolyte delivered a high reversible capacity of 141.1 mA h g⁻¹ and a high retention rate of 85.8% after 10 000 cycles at 1 A g⁻¹. Even after 17 000 cycles at 5 A g⁻¹, the reversible capacity remained stable at 106.2 mA h g⁻¹ with a high retention rate of 90.1%. The corresponding pouch batteries with a high iodine loading of 12.7 mg cm⁻² exhibit a high capacity of 165.8 mA h g⁻¹ and a 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 a durable cyclic stability of Zn–I₂ batteries.