Stretchable and conductive cellulose hydrogel electrolytes for flexible and foldable solid-state supercapacitors

In this study, the anti-freezing conductive hydrogel electrolytes with outstanding mechanical properties were synthesized by a facile and feasible method. The mechanical and anti-freezing properties of the synthesized polyacrylamide/lithium lhloride/water soluble cellulose acetate (PAM/LiCl/WSCA) hydrogels are significantly enhanced with the addition of WSCA and LiCl. The tensile strength and toughness of the gels were gradually increased to 341 KPa and 1.2 MJ/m3, respectively. The hydrogel electrolyte can remain soft and flexible at -80 °C, displaying certain elasticity and electrical conductivity. In addition, the super-capacitor assembled with PAM/LiCl/WSCA hydrogel as electrolyte showed excellent stability in capacitance retention after 500 times of folding cycles and 10,000 times of charge and discharge tests. The capacitor still maintains 64.64 % of its capacity at -40 °C. This facile strategy to fabricate anti-freezing conductive hydrogel electrolyte provides a new idea and way to the application of hydrogels as electrolytes in extreme cold environments.