Wide-Temperature Flexible Supercapacitor of Organohydrogel Electrolyte and Its Combined Electrode.

Abstract

Hydrogel-based flexible supercapacitors possess the merits of highly ionic conductivity and superior power density, but the existence of water limits their application in the extreme temperature scenarios. Noticeably, it is a challenge for people to design more extremely temperature adaptable systems for flexible supercapacitor based on hydrogel with wide-temperature region. In this work, a wide-temperature flexible supercapacitor that can operate at -20-80 °C is fabricated by the organohydrogel electrolyte and its combined electrode (also known as electrode/electrolyte composite). By introducing highly hydratable LiCl into ethylene glycol (EG)/H2O binary solvent, owning to the ionic hydration effect of LiCl and hydrogen-bond interaction between EG and H2O molecules, the organohydrogel electrolyte exhibits satisfactory freezing resistance (-113.9 °C of freezing point), anti-drying capability (78.2% of weight retention after vacuum drying at 60 °C for 12 hours) and excellent ionic conductivity both at room temperature (13.9 mS/cm) and low temperature (6.5 mS/cm 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, power density of 160 W/kg and energy density of 13.24 Wh/kg at the current density of 0.2 A/g. The initial capacitance can maintain 100% after 2000 cycles at 1.0 A/g. More importantly, the specific capacitances can be well maintained even at -20 °C and 80 °C. With other advantages such as excellent mechanical property, the supercapacitor is an ideal power source suitable for various working conditions.