CONDUCTING POLYMERS AS ACTIVE MATERIALS IN ELECTROCHEMICAL CAPACITORS

Electronically conducting polymers represent an interesting class of materials for use in electrochemical capacitors thanks to the combination of high capacitive energy density and low materials cost. Three generalized types of electrochemical capacitors can be constructed using conducting polymers as active material, and in the third of these, which utilizes conducting polymers that can be both n- and p-doped, energy densities of up to 39 Wh per kg of active material on both electrodes have been demonstrated. This energy density is obtained using poly-3-(4-fluorophenyl)-thiophene (PFPT) in an electrolyte of 1 M tetramethylammonium trifluoromethanesulfonate (TMATFMS) in acetonitrile. This unique system exhibits reversible n- and p-doping to high charge density in relatively thick films of the active polymer and a cell voltage exceeding 3 V in the fully charged state. Impedance data for both n- and p-doped PFPT suggest that high power densities can be obtained in electrochemical capacitors based on this active conducting polymer.