A robust dual-network hydrogel electrolyte coupled with a porous carbon material for flexible quasi-solid-state zinc ion hybrid supercapacitors

As an emerging energy storage device, zinc ion hybrid supercapacitors (ZHSCs) have attracted wide interest because of their intrinsic safety, high energy/power densities, and long cycle life. However, problems of liquid leakage and zinc dendrite growth seriously hinder its widespread application. To solve the above problems, a gelatin/polyacrylamide/agarose/Zn(CF3SO3)2 hydrogel electrolyte (G/PAAm/AG/Zn(CF3SO3)2) was designed by constructing a multi-crosslinked network of physically crosslinked gelatin and agarose coupled with chemically crosslinked polyacrylamide. The tested results show that G/PAAm/AG/Zn(CF3SO3)2 can effectively prevent electrolyte leakage and inhibit zinc dendrite growth. Moreover, G/PAAm/AG/Zn(CF3SO3)2 possesses high ionic conductivity (2.64 S m-1), high tensile strength (72.4 kPa at 489.2%), and high compressive strength (164.5 kPa at 80%). Additionally, a highly connected porous carbon material (denoted as HSSPC) with high specific surface area (2930.9 m2 g-1) was synthesized, which exhibits a reversible capacity of 183.5 mA h g-1 and good cycling stability (the capacity remains at 96.6% after 10 000 cycles). More importantly, the quasi-solid-state ZHSC based on G/PAAm/AG/Zn(CF3SO3)2 and HSSPC delivers a high specific capacity (122.8 mA h g-1, 0.25 A g-1), high energy/power densities (96.1 Wh kg-1/14.4 kW kg-1), and good cycling stability (capacity retention can be maintained at 114.0% of the initial capacity after 14 000 cycles). A hydrogel electrolyte was designed by constructing a multi-crosslinked network. The quasi-solid-state ZHSC based on the hydrogel electrolyte and HSSPC delivers a high specific capacity, high energy/power densities, and good cycle stability.