Directionally Cast Multilevel Channels in Hydrogel Electrolyte for Low‐Temperature Aqueous Zinc‐Ion Batteries

Abstract Aqueous zinc‐ion batteries have attracted widespread attention due to their high safety and energy density. However, their practical application is hindered by insufficient low‐temperature performance and rampant side reactions on Zn metal anode. In this work, a freeze‐casting method is utilized to acquire the unidirectional and multilevel pore structure in polyvinyl alcohol (PVA)‐based hydrogel. Then, strengthen the PVA chain and rearrange its hydrogen bonds via a solution substitution process. The ordered arrangement of molecular chains, formation of multilevel channels, and introduced glycerin enhance the mechanical properties, water‐retention and anti‐freezing capability of the hydrogel. Hence, the hydrogel electrolyte can effectively suppress side reactions at the anode interface, while enabling stable and fast Zn 2+ ion transport. Consequently, it realizes a high average Coulombic efficiency of 99.2% of the Zn||Cu cell and a long lifespan of 1200 h of the Zn||Zn cell. When coupled with the NH 4 V 4 O 10 cathode, it delivers the faster electrochemical reactions kinetics and an excellent capacity retention rate of 87.3% after 1130 cycles. Even under an ultralow temperature of −20 °C, the designed hydrogel can still endow fast and stable Zn deposition/stripping cycles. This work provides a feasible design strategy for the development of hydrogel electrolytes for low‐temperature aqueous zinc‐ion batteries.