Polypyrrole/carbon composite electrode for high-power electrochemical capacitors

Nano-thin polypyrrole (PPy) layers with thickness from similar to 5 run to several 10s run were deposited oil vapor grown carbon fibers (VGCF) by an in situ chemical polymerization. Using different concentrations of the pyrrole could control the thicknesses of deposited PPy layers. Surface morphology and thickness of the deposited PPy layers were confirmed by means of scanning electron microscopy and scanning transmission emission microscopy. Pseudo-capacitive behavior of the deposited PPy layers on VGCF investigated by means of cyclic voltammetry. Then, the PPy/VGCF composites were mixed with activated carbons (AC) at various mixing ratios. For the PPy/VGCF/AC composite electrodes. characteristics of specific capacitance and power capability were examined by half-cell tests. As results of this study, it was investigated that nano-thin PPy layer below similar to 10 nm deposited on VGCF had high pseudo-capacitance and fast reversibility. Its specific capacitance per averaged weight of active material (PPy) was obtained as similar to 588 Fg(-1) at 30 mV s(-1) and maintained as similar to 550 F g(-1) at 200 mV s(-1) of scan rate. Also, from the mixing, 60 wt.% of the PPy/VGCF with 25 wt.% of AC, the PPy/VGCF/AC composite electrode exhibited higher power capability maintaining the specific capacitance per active materials of PPy and AC as similar to 300 Fg(-1) at 200 mV s(-1) in 6 M KOH. (c) 2006 Elsevier Ltd. All rights reserved.