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

Abstract

AbstractHydrogel‐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)/H2O binary solvent, owing to the ionic hydration effect of LiCl and the hydrogen bond interaction between EG and H2O 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.