Liner-chain polysaccharide binders with strong chemisorption capability for iodine species enables shuttle-free zinc-iodine batteries

Abstract

Designing functional binders is demonstrated an effective solution to address the serious issues of active iodine dissolution and polyiodide shuttle faced by aqueous zinc-iodine batteries (AZIBs). Herein, a series of linear-chain polysaccharides are systematacially investigated as the potential water-soluble binders for iodine-loading cathode of AZIBs. According to the results of spectral characterizations and theoretical calculations, SA binder, as the representative of polysaccharides, is verified with strong chemisorption capability and high binding energy for the iodine intermediates owing to the existence of active ether and carboxyl groups, which contributes to suppress the polyiodide shuttle and active iodine dissolution. Meanwhile, the lower Gibbs free energy values indicate the introduction of SA binder is conducive to boost the iodine redox reaction kinetics of iodine-loading cathode. Benefitting from these merits, the Zn//CAC@I₂ batteries with SA biner delivers superior self-discharge resistance capability, excellent rate performance, and ultra-durable cycling stability with high reversible capacity of 105.2 mAh g⁻¹ after 8000 cycles at 1 A g⁻¹ and 86.3 mAh g⁻¹ after 40,000 cycles at 5 A g⁻¹, respectively. This work will enlighten the research and development of binder materials for advanced iodine-based energy storage devices, and facilitate the practical application of both polysaccharide binders and AZIBs.