Mechanically Strong and Tough Ionic Liquid Gel Electrolyte for Four-Electron Zinc–Iodine Batteries

Interfacial stress accumulation and dendrite penetration constitute the fundamental origins of cycle life degradation in solid-state zinc ion batteries, necessitating polymer electrolytes with both high mechanical strength and high toughness. Nevertheless, constructing double-high-polymer electrolytes through molecular design to enhance dynamic interface compliance remains a persistent challenge. In this study, to achieve long-term stabilized Zn chemistry, a supramolecular ionic liquid gel electrolyte was developed by a solvent exchange process through noncovalent interaction, which consists of PVA and ionic liquid (IL, Bmim[ZnBr₃]/Bmim[ZnCl₃]). The stable supramolecular effect (Br–H bond and H-bond) of IL endows the electrolyte with high strength (2.22 MPa tensile strength, more than 1200% deformation) and high toughness (1900.74 MJ/m³), and the long-term cycle life of the anode (over 2000 h) can be achieved through the unique stress dissipation mechanism. Besides, the polyanionic groups ([ZnBr₃]⁻) of IL activate the −OH site activity of PVA by changing the distribution of electrons, which enhance binding of Zn²⁺ to the site, realizing a high Zn²⁺ transference number (0.61) and ionic conductivity (0.739 mS cm^–1). In addition, the low water content and Br^–-rich chemical environment contribute to the formation of [IBr₂]⁻ polyhalide via interhalogen nucleophilic interactions, stabilizing the realization of the iodine four-electron reaction (0.2 A g^–1, 4000 cycles).