Integrating PVA-HPC matrix with DMSO as a promising hydrogel electrolyte for zinc ion batteries

Aqueous zinc–ion batteries offer a safe, low-cost and sustainable option for energy storage, but their practical deployment is hindered by dendrite formation, hydrogen evaluation, corrosion, and severe capacity loss at subzero temperatures. Hydrogel electrolytes improve safety, compatibility, and mechanical robustness, but often fail to maintain performance under freezing conditions. Here, a composite ZnSO4 electrolyte membrane has been developed, based on a crosslinked hydrogel formed by incorporating hydroxypropyl cellulose (HPC) into a polyvinyl alcohol (PVA) network and adding dimethyl sulfoxide (DMSO) as an anti-freezing agent, referred to as PVA/HPC@DMSO (PHD). After soaking in 2.5 M ZnSO4 + 0.2 M MnSO4 (ZM) solution, the resulting composite PHD-ZM exhibits superior ionic conductivity of 49.7 mS · cm−1 at 25 °C and 27.6 mS · cm−1 at 0 °C, along with excellent mechanical properties achieving a tensile strength of ∼1.5 MPa at ∼700% elongation. PHD remains highly flexible, bendable and stretchable below −20 °C. As the elctrolyte in in Zn//Zn symmetrical cells, PHD-ZM enables excellent stability at 25 °C for 1000 h at 1 mA · cm−2, and over 400 h at 2.5 mA · cm−2, with no dendrite formation after 1000 h cycling. A Zn/MnO2 full cell battery using PHD-ZM delivered high capacities of 388 mAh · g−1 at 0.1 A g−1 at 25 °C and maintained stable as 200 mAh g−1 at 1.2 A · g−1 for over 1000 cycles. At 0 °C, the Zn/MnO2 full cell retains 190 mAh g−1 at 1.2 A g−1 for over 100 cycles. The battery capacity achieved 364 mAh g−1 at 0 °C and 316 mAh · g−1 at −20 °C under a c-rate of 0.1 A g−1, corresponding 94% and 82% capacity retention relative to 25 °C. These results demonstrate that PHD-ZM combines high ionic conductivity, flexibility, mechanical strength, and excellent low temperature tolerance, making it a promising electrolyte for aqueous batteries, or other electrochemical devices.