A nanocomposite electrode of single-walled carbon nanotube ͑SWNT͒ and polypyrrole ͑Ppy͒ is fabricated to improve the specific capacitance of the supercapacitor. The individual nanotubes and nanoparticles are uniformly coated with Ppy by in situ chemical polymerization of pyrrole. To characterize the SWNT-Ppy nanocomposite electrodes, a charge-discharge cycling test for measuring specific capacitance, cyclic voltammetry, and an ac impedance test are executed. The SWNT-Ppy nanocomposite electrode shows much higher specific capacitance than pure Ppy and as-grown SWNT electrodes, due to the uniformly coated Ppy on the SWNTs. The effects of the conducting agent added in the nanocomposite electrodes on specific capacitance and internal resistance of supercapacitors are also investigated.

We have fabricated electrodes for a supercapacitor using fluorinated single-walled carbon nanotubes (SWCNTs). Although the specific surface areas of the pristine and fluorinated SWCNTs are similar, the electrochemical reactions are different significantly from each other. The specific capacitance of the fluorinated SWCNTs is smaller than that of the pristine sample particularly at large discharge current density, which can be attributed to the micropores formed during fluorination. After heat treatment at 900 °C for 30 min, the nonredox reaction is dominant, and furthermore, the fluorinated sample gives a larger specific capacitance than the pristine sample.