Structural Composite Hydrogel Electrolytes for Flexible and Durable Zn Metal Batteries

Abstract Hydrogel electrolytes consisting of salt ions, water solvents, and 3D polymer networks play the roles of an electrolyte and a separating membrane. These are receiving attention as a substitute for the currently used liquid electrolyte/separator materials in aqueous Zn metal batteries (AZMBs). In this study, a structural composite hydrogel electrolyte is designed by incorporating layered alumina microplatelets within a polymer matrix to achieve high mechanical strength, stiffness, hardness, thermal conductivity, and a large dielectric constant. The hydrogel electrolyte simultaneously achieves mechanical robustness and fast Zn ion transfer, enabling uniform Zn deposition without notable dendrite growth and propagation. Moreover, the rapid heat‐dissipating ability of the electrolyte demonstrates the potential for effective thermal management of AZMB cells. Consequently, Zn||Zn symmetric cells composed of the as‐designed electrolyte exhibit stable Zn plating/stripping behavior at various temperatures. Zn||poly(3,4‐ ethylenedioxythiophene)‐vanadium pentoxide (PVO) full cells have large energy densities of 356.9 W h kg −1 at 25 °C and 216.6 W h kg −1 at −20 °C and long‐term stability over 1,000 cycles. Further, pouch‐type Zn||PVO full cells with large energy densities operate stably while bent, folded, rolled, cut in half, or immersed in boiling and freezing water.