Wide-Temperature Flexible Supercapacitor from an Organohydrogel Electrolyte and Its Combined Electrode

Hydrogel-based flexible supercapacitors possess the merits of highly ionic conductivity and superior power density, but the existence of water limits their application in extreme temperature scenarios. Noticeably, it is a challenge for people to design more extremely temperature adaptable systems for flexible supercapacitors based on hydrogels with a wide temperature region. In this work, a wide-temperature flexible supercapacitor that can operate at -20-80 °C was fabricated by an organohydrogel electrolyte and its combined electrode (also known as an electrode/electrolyte composite). Upon introducing highly hydratable LiCl into an ethylene glycol (EG)/H₂ O binary solvent, owing to the ionic hydration effect of LiCl and the hydrogen bond interaction between EG and H₂ O molecules, the organohydrogel electrolyte exhibits satisfactory resistance to freezing (freezing point of -113.9 °C), anti-drying capability (78.2 % of weight retention after vacuum drying at 60 °C for 12 h) and excellent ionic conductivity both at room temperature (13.9 mS cm^-1 ) and low temperature (6.5 mS cm^-1 after 31 days at -20 °C). By using organohydrogel electrolyte as binder, the prepared electrode/electrolyte composite effectively reduces interface impedance and enhances specific capacitance due to the uninterrupted ion transport channels and extended interface contact area. The assembled supercapacitor delivers a specific capacitance of 149 F g^-1 , a power density of 160 W kg^-1 , and an energy density of 13.24 Wh kg^-1 at a current density of 0.2 A g^-1 . The initial 100 % capacitance can be maintained after 2000 cycles at 1.0 A g^-1 . More importantly, the specific capacitances can be well maintained even at -20 and 80 °C. With other advantages such as excellent mechanical property, the supercapacitor is an ideal power source suitable for various working conditions.