Hybrid supercapacitor materials from poly(3,4-ethylenedioxythiophene) conformally coated aligned carbon nanotubes

Conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) conformally coated aligned carbon nanotubes (PEDOT/A-CNTs) were developed and investigated as the active material for supercapacitor electrode applications and the results were compared to those of non-coated CNTs as well as that of PEDOT coated randomly packed CNTs. The electrochemical performance of the electrodes was evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS). The results revealed that the PEDOT conformally coated and densified (5% volume fraction, Vf) A-CNTs exhibit a specific volumetric capacitance of 84.0 F/cm3, much higher compared to the non-coated and non-densified A-CNTs (1% Vf) that had a specific capacitance of only 3.9 F/cm3. Ion insertion/de-insertion processes in the PEODT coating layers are observed in impedance spectra for the PEDOT-coated A-CNT electrodes at rates that are not limiting to cell performance relative to ion transport through the channels formed by the PEDOT/A-CNTs. Specific energy and power densities of 11.8 Wh/l and 34.0 kW/l, respectively, were obtained for these nano-tailored electrodes, with high capacitance retention compared with those of PEDOT coated random CNTs.