Multifunctional Hydrogel Electrolyte Synergizing with Free-Standing Cathode Enables Robust Aqueous Zinc Metal Batteries

Abstract

Aqueous zinc metal batteries (AZMBs) have attracted increasing attention due to their low cost and high energy density. However, their practical applications are constrained by Zn dendritic growth, self-corrosion, and poor low-temperature adaptability. Herein, a multi-component hydrogel electrolyte is proposed to address these challenges. Specifically, dimethyl sulfoxide is added to substitute H₂O in the Zn²⁺ solvation sheath and disrupt the intrinsic H─bond network, suppressing interfacial parasitic reactions induced by active water and achieving ultra-low freezing point (−60 °C); while the acylamino groups on polyacrylamide chains are utilized to coordinate with Zn²⁺ and SO₄²⁻, leading to homogeneous Zn²⁺ flux and reduced by-products accumulation. Benefitting from the synergistic effects, stable Zn plating/stripping with high average Coulombic efficiency of 99.5% for 1200 h at 0.5 mA cm⁻² is achieved. To manifest the superiority of the hydrogel electrolyte, free-standing α-MnO₂/single-walled carbon nanotube film is designed as cathode. The resulting AZMB exhibits large specific capacity, prominent rate capability (157.5 mAh g⁻¹ at 10 C), high cyclic stability, and good low-temperature performance (68.8% capacity retention at −20 °C), which also demonstrates excellent safety under extreme conditions of hammering, cutting, burning, punching, and soaking. This work provides an inspired strategy to build robust, multi-functional, inexpensive aqueous batteries.