Hydrogel electrolytes for zinc dendrite regulation: balancing conductivity and modulus

Abstract

Hydrogels, composed of water and polymer networks, have emerged as promising electrolytes for aqueous zinc batteries due to their inherent compatibility with aqueous systems. However, a trade-off typically exists; soft hydrogels exhibit high ionic conductivity but low mechanical strength, whereas mechanically robust hydrogels offer high modulus at the expense of reduced conductivity. The optimal balance between these properties for stabilizing zinc anodes remains unclear. In this work, we present a robust hydrogel electrolyte based on neutral polymers, featuring a moderate ionic conductivity (∼3 mS cm⁻¹) and a high Young's modulus (∼20 MPa). Compared to conventional liquid electrolytes and mechanically weak hydrogels (∼2 MPa, ∼50 mS cm⁻¹), the high-modulus hydrogel electrolyte demonstrates markedly enhanced capability in terms of dendrite suppression. Experimental and simulation results reveal that a stiffer hydrogel promotes a favorable coupling between interfacial kinetics and ion transport, contributing to a lower characteristic Damkohler number. This facilitates a more uniform ion flux and optimal electrode kinetics at the zinc electrode interface. Overall, this study highlights the pivotal role of mechanical modulus in regulating Zn deposition and offers valuable guidance for the rational design of hydrogel electrolytes with enhanced stability and performance in aqueous zinc batteries.