A novel hydrogel electrolyte for all-climate high-performance flexible zinc-ion hybrid capacitors within temperature range from −50 to 100 °C

Zinc-ion hybrid capacitors (ZIHCs) combining advantages of battery and supercapacitor represent a promising type of energy storage system for flexible electronics, but often suffer from limited performance stability in low or high temperature. Here, we demonstrate a type of high-performance flexible ZIHCs under all-climate from −50 to 100 °C enabled by a novel hydrogel electrolyte, which is synthesized by acrylamide, λ-carrageenan and zinc perchlorate. The three-dimensional porous structure of hydrogel can efficiently facilitate ion transport, while the formed hydrogen bonds among zinc perchlorate, water and polymer chains could largely broaden the operating temperature of the hydrogel. The hydrogel electrolyte exhibits ionic conductivities of 9.75, 45.98 and 57.14 mS cm−1 at −50, 25 and 100 °C, respectively, which indicates superior stability under all-climate environment to other previously reported results. Based on the hydrogel electrolyte, the developed ZIHCs not only exhibit high specific capacity of 125 mAh g−1 at room temperature, but also can work well within an extremely wide temperature from −50 to 100 °C. In addition, the ZIHCs possess excellent flexibility with capacity retention of 98% after 2000 bending cycles to 135°. This work provides a promising strategy to design high-performance flexible ZIHCs working in all-climate environment for flexible electronics.