Preparation and Characterization of Micro Polypyrrole Electrodes for Supercapacitor

Abstract

A novel electrode of supercapacitor was developed with a three dimensional (3D) structure which results in a significant increase of the electrode area per unit capacitor volume. An area of 2.58 times the area of corresponding planar design was obtained. The process flow for fabricating the 3D electrode was developed compatible with microelectromechanical system technology. The key processes were high-aspect-ratio Deep Reactive Ion Etching, electroless plating and electropolymerization. Ni as the current collector was deposited on Si/SiO2 substrate by using electroless plating, Polypyrrole was galvanostatically polymerized as electroactive film. The capacitance properties of the 3D electrode were investigated. Cyclic voltammetry tests show that the specific capacitance of the 3D electrode at 100 mV/s was 0.014 F/cm2 which is comparable with the 0.013 F/cm2 for the planar design. Electrochemical impedance spectroscopy plot of the 3D electrode is well fitted by equivalent circuit, we found the specific capacitance is 0.011 F/cm2 which is slightly larger than 0.0094 F/cm2 for similarly planar design. From the gavanostatic charge/discharge tests, the specific capacitance of the 3D electrode at 2 mA/cm2 is 0.011 F/cm2 while for planar design the corresponding value is 0.010 F/cm2. The results indicate the continuous and homogeneous Polypyrrole film with 3D structure was obtained as we designed.