Rational Design of Antifreezing Organohydrogel Electrolytes for Flexible Supercapacitors

Hydrogel electrolytes have gained significant attention in the field of flexible supercapacitors for their intrinsic safety, high flexibility, and superior ionic conductivity. However, the water-rich structures of traditional hydrogel electrolytes inevitably cause them to freeze at subfreezing temperatures, which therefore limits the application of flexible supercapacitors at extremely cold temperatures. Herein, an organohydrogel electrolyte was successfully fabricated by displacing a portion of water molecules from hydroxypropyl cellulose/poly(vinyl alcohol) (HPC/PVA) hydrogel with LiClO4 water/glycerol mixture solution. The introduction of glycerol and inorganic salt into the hydrogel matrix can effectively preclude the ice formation of water at subfreezing temperatures. The flexible supercapacitor comprising the optimal antifreezing organohydrogel electrolyte exhibited excellent mechanical and electrochemical stability at subfreezing temperatures. Even if the temperature decreased to −40 °C, the supercapacitor could also deliver a specific capacitance of 143.6 F g–1 (73.75% of the one delivered at 20 °C) with Coulombic efficiency approaching ∼100%. Meanwhile, the electrochemical performance of the supercapacitor could also be well maintained under different bending conditions. It is believed that this work will play an exemplary role for designing antifreezing gel electrolytes for flexible energy storage devices using at extremely cold environments.