A Quasi-Solid Ionic Liquid-Polymer Hybrid Electrolyte for Shuttle-Free and Dendrite-Free Aqueous Zinc─Bromine Batteries.

Abstract

Aqueous static zinc─bromine (Zn─Br) batteries hold promise for grid-scale energy storage but still suffer from severe polybromide shuttling and poor Zn reversibility. Here, we develop a quasi-solid ionic liquid-polymer hybrid electrolyte by integrating a sulfonated polymer matrix with anchored 1-butyl-3-methylimidazolium (BMI⁺) cations. The fixed -SO₃ ^- groups construct highly Zn²⁺ selective conduction channels, while BMI⁺ forms strong electrostatic interactions with the polymer, generating immobilized ionic-liquid domains that effectively capture polybromides. This hybrid design transforms BMI⁺ from a soluble additive into a structural component of the quasi-solid framework, thereby enabling simultaneous dendrite-free Zn plating/stripping and shuttle suppression. With this multifunctional regulation, the Zn─Br batteries achieve a high initial capacity of 162.7 mAh g^-1, a discharge plateau of ∼1.78 V, and 25 000-cycle durability at 20 C. Moreover, the pouch cell with high-loading Br cathodes (∼14 mg_KBr cm^-2) retains 90.9% capacity after 1500 cycles. This work demonstrates that quasi-solid ionic liquid-polymer hybrid electrolytes can deliver shuttle-free, long-lasting Zn─Br batteries, pointing to a promising pathway for scalable and reliable aqueous energy storage.