An Environmentally Benign Supercapacitor Using A Water-dissolvable Ionic Gel

An environmentally benign supercapacitor is developed incorporating an ionic liquid, carbon powder, a cellulose separator and a Molybdenum electrode. The ionic liquid is dispersed into a water-dissolvable polymer, poly(vinyl alcohol), to produce solid electrolyte, so-called an ionic gel. A carbon composite mixed with the ionic liquid maintains a gel form. The ionic gel and the carbon composite enable an all-solid-state supercapacitor which can be charged at the voltage of 1.5 V. The supercapacitor shows areal and volumetric capacitance of 65 mF/cm2 and 2.2 F/cm3. A cycle test reveals that capacitance retention and coulombic efficiency are 77% and 90%, respectively. As for dissolution test, the ionic gel and carbon composite dissolves into phosphate buffer solution in 18 days, and the Mo electrode is able to fully dissolve in 500~588 days. Potential applications of the environmentally benign supercapacitor include smart agriculture by monitoring of soil, disaster prevention by the wireless sensor network without need for retrieval of devices after use.