Electrochemical storage of polypyrrole–Fe 2O 3 nanocomposites in ionic liquids

Abstract

Electroactive polypyrrole–Fe 2O 3 nanocomposite materials were prepared by chemical polymerization of pyrrole in aqueous Fe 2O 3 colloidal solution, using FeCl 3 as oxidant and tosylate anions (TS) as doping agent. The nanocomposite material named (PPyTSNC) was studied by X-ray diffraction analysis, Fourier Transform Infra-Red spectroscopy and thermogravimetric analysis. Their electrochemical storage properties were investigated on composite electrodes using 80% in weight of active materials in different immidazolium and pyrrolidinium based room temperature ionic liquids (RTILs) as electrolytes. Cyclic voltammetry and constant current charge discharge cycling showed high charge storage properties of the nanocomposite based electrodes in 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide (EMITFSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14TFSI) (respectively 72 mAh/g and 62 mAh/g at 1 mA/cm 2 discharge current) which are more than twice higher than the values obtained with pure PPy. These improvements in capacities have been attributed to the PPyTSNC morphology modification which ensures a large incorporation of the electrolyte inside the nanostructure. The specific capacitances of the nanocomposite electrodes reached 210 F/g and 190 F/g in EMITFSI and PYR 14TFSI and their cyclability has shown only 3–5% capacitance loss after one thousand cycles for both ionic liquids.