Tough and redox-mediated alkaline gel polymer electrolyte membrane for flexible supercapacitor with high energy density and low temperature resistance

To meet the practical application requirements of the flexible supercapacitors, the improvements of the toughness and energy density attract more and more attention. Herein, a physically cross-linked double network alkaline gel polymer electrolyte (AGPE) membrane based on PVA and kappa-carrageenan is developed. In this AGPE membrane, KOH plays a dual role including carrier donator and ion cross-linker, which makes the AGPE membrane show the unique improvement of ionic conductivity (0.31 S/cm) and mechanical properties (tensile strength of 1.62 MPa and tensile elongation of 670%) at the same time. In order to improve energy density, the redox-active mediator p-phenylene diamine has been introduced in the AGPE membrane, endowing the fabricated supercapacitor with high electrode specific capacitance (741 F/g) and energy density (18.3 Wh/kg) with a maximum power density of 800 W/kg. Meanwhile, the supercapacitor can exhibit great flexibility and toughness, and maintain stable capacitance performance under bending and stretching state. Moreover, the supercapacitor shows an excellent low temperature resistance and it is able to maintain 82% of its room-temperature capacitance even at -40 °C. This investigation offers a strategy to prepare gel polymer electrolyte membrane with high adaptive ability of deformation and low temperature, which has potential application in various flexible, portable and wearable electronics.