Performance Evaluation of Poly 3-(Phenylthiophene) Derivatives as Active Materials for Electrochemical Capacitor Applications

Electroactive polymers from 3-(4-fluorophenyl)thiophene, 3-(4-cyanophenyl)thiophene, 3-(4-methylsulfonylphenyl)thiophene, and 3-(3,4-difluorophenyl)thiophene were electrochemically deposited onto carbon paper electrodes from tetramethylammonium trifluoromethanesulfonate (Me 4 NCF 3 SO 3 )/acetonitrile and/or tetraethylammonium tetrafluoroborate (Et 4 NBF 4 )/acetonitrile electrolyte solutions. The morphologies and electrochemical performance of the films were shown to depend on both the growth and cycling electrolytes. Constant current multicycle tests were performed on model single-cell devices using the type III capacitor configuration at high voltage (2.8−2.9 V). Active material energy and power densities of up to 50 Wh/kg and 5 kW/kg were achieved at discharge rates of 50 and 10 mA/cm 2, respectively. The long-term stabilities (up to 1000 cycles) of these polymers were investigated by repeated charging and discharging using cyclic voltammetry in both the p- and n-doping regimes.