Sulfonated Lignin Binder Blocks Active Iodine Dissolution and Polyiodide Shuttle Toward Durable Zinc-Iodine Batteries

Abstract

The issues of active iodine dissolution and polyiodide shuttle severely hinder the development of zinc-iodine batteries (ZIBs). Binder engineering is considered a valid strategy to kill two birds with one stone. Herein, sodium lignosulfonate (LS), an important derivative of lignin, is optimized as a neotype binder for the fabrication of an iodine-loading cathode. Owing to the existence of the -SO₃Na group, the electrostatic potential of LS molecule contains both negative and positive regions, which prefer to block the polyiodide shuttle behavior through the electrostatic repulsion effect, and adsorb the polyiodides through the electrostatic attraction effect, respectively. Meanwhile, LS molecule holds more negative Gibbs free energies for the consecutive radical reaction, and much stronger adsorption energies for iodine species, manifesting fast iodine conversion reaction kinetics, and effective inhibition for iodine dissolution behavior. As expected, the ZIBs based on LS binder delivers a high capacity of 153.6 mAh g⁻¹ after 400 cycles at 0.1 A g⁻¹, reversible capacity of 152.8 mAh g⁻¹ after 500 cycles at 0.5 A g⁻¹ (50 °C), and durable cycling stability for 12000 cycles at 5 A g⁻¹, implying excellent iodine fixation ability of LS binder. This work guides the design of a special binder for iodine-based electrodes and facilitates the practical application of ZIBs.