Electrochemical storage of polypyrrole-Fe2O3 nanocomposites in ionic liquids

Electroactive polypyrrole-Fe2O3 nanocomposite materials were prepared by chemical polymerization of pyrrole in aqueous Fe2O3 colloidal solution, using FeCl3 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 (PYR14TFSI) (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 PYR14TFSI and their cyclability has shown only 3-5% capacitance loss after one thousand cycles for both ionic liquids. (C) 2008 Elsevier Ltd. All rights reserved.