Agar-based hydrogel polymer electrolyte for high-performance zinc-ion batteries at all climatic temperatures

Aqueous zinc-ion batteries (ZIBs) have received numerous attention because of their inherent safety and low cost. However, ZIBs are highly sensitive to temperature; the realization of full-temperature ZIBs is of great importance. In this study, an agar-based composite hydrogel polymer electrolyte (AG-HGPE) with the blend of agar and polyacrylamide (PAM) was prepared. It has a non-porous homogeneous structure, and shows various merits, e.g., strong liquid absorption rate, good mechanical properties, and large Zn²⁺ transference number. The corresponding Zn-symmetric cells possess reversible zinc stripping/plating phenomenon up to 500 h at a current density of 1 mA cm^-2 and an areal capacity of 1 mAh cm^-2. The Zn/AG-HGPE/V₂O₅ cells exhibit good rate performance and stable cyclic behaviors at -25°C, 25°C and 50°C, as well as excellent adaptability to the changes of ambient temperature. The research paves a new route for developing green energy storage devices running in wide temperature range.