Building a High-Performance Zn–I2 Battery with a Green and Affordable Cationic Cellulose Binder

Despite showing low cost, inherent safety, and high suitability, the rechargeable Zn–I₂ aqueous batteries are still seriously suffering from self-discharge and energy density issues stemming from I₂ dissolution, polyiodide shuttling, and low I₂ mass loading. Herein, we develop a novel polyquaternium-10 (P10, a cationic cellulose)-based binding system to simultaneously circumvent these issues. The water-borne P10 binder can suppress I₂ dissolution and polyiodide shuttling by not only adsorbing polyiodides via its quaternary ammonium groups and oxygen heteroatoms but also eliminating the use of toxic, expensive, and I₂-dissolving organic solvents (e.g., N-methylpyrrolidone, NMP), enabling a facile and green cathode-fabricating process. More importantly, the P10 binder is conducive to the preparation of thick cathode coatings with high I₂ mass loadings, thanks to its high elasticity and mechanical toughness after swelling by the electrolyte. As a result, Zn–I₂ batteries prepared with the P10 binder demonstrate much better anti-self-discharge performance than those prepared with conventional PVDF binders (capacity retention: 84 vs 63% after 200 h of open-circuit storage). Even at an ultrahigh I₂ mass loading of 14.5 mg cm^–2, the batteries can still deliver significant specific capacity (216 mAh g^–1) and cyclability (96.8% capacity remained after 385 cycles). This binder should be highly compatible with other performance-improving strategies, providing a green yet affordable approach for the construction of high-performance Zn–I₂ aqueous batteries.