Quasi-solid-state pseudocapacitors using proton-conducting gel polymer electrolyte and poly(3-methyl thiophene)–ruthenium oxide composite electrodes

Abstract

We report the studies on a flexible quasi-solid-state configuration of the redox supercapacitors (pseudocapacitors) assembled with an ionic liquid-based proton conducting non-aqueous gel polymer electrolyte (ILGPE) and composite electrodes of conducting polymer [poly-3-methyl thiophene (pMeT)] and hydrous ruthenium dioxide (RuO2.xH2O). The presence of RuO2.xH2O in the composite electrodes has been confirmed by X-ray diffraction and thermogravimetric analysis. The ILGPE films, prepared with the solution of an ionic liquid (1-ethyl 3-methyl imidazolium trifluoromethanesulfonate) and a salt ammonium trifluoromethanesulfonate entrapped in a host polymer poly(vinylidene fluoride-co-hexafluoropropylene), have been characterized. The symmetrical pseudocapacitors have been assembled and characterized using electrochemical impedance spectroscopy, cyclic voltammetry, and charge–discharge tests. The composite electrodes with the ∼13 wt.% hydrous RuO2 loading in pMeT film has shown a maximum specific capacitance value of ∼118 F g−1 (of the composite electrode material). The corresponding maximum specific energy and power density have been found to be ∼12.8 W kg−1 and ∼513 W kg−1, respectively. With further increase in the content of RuO2.xH2O, a slight decrease in specific capacitance value has been observed, which indicates the reduction in utilization rate of RuO2.xH2O. The composite electrodes show stable capacitance values up to 5,000 charge–discharge cycles.