New composite electrodes made of polypyrrole and graphite: Construction, optimization and characterization

In this work, new composite electrodes were developed, optimized and characterized for possible, future use in batteries and/or super-capacitors. These composite electrodes were prepared from chemically synthesized polypyrrole (Ppy), graphite carbon and Teflon and their physico-chemical performances were tested using different techniques. Their conductivity and porosity were investigated under various conditions. Their macroporous structure was also studied by the BET method. Two distinct electrochemical reactions were found to take place at these electrodes, including a redox reaction with insertion and expulsion of anions, and a capacitive reaction at the electrode/electrolyte interface. The specific capacity, experimentally obtained with an electrode containing 40 wt% of Ppy (99.6 mAh g−1), was larger than the theoretical one, due to double-layer effects at the Ppy/electrolyte interface. The double-layer capacitance at the electrode/electrolyte interface of the composite electrodes, investigated by electrochemical impedance spectroscopy, was found to represent at most 0.1% of the total electrode capacitance.