Polypyrrole/carbon composite electrode for high-power electrochemical capacitors |
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Authors: | Jong-Huy Kim Yong-Sung Lee Chen G. Liu |
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Affiliation: | a Energy Conversion and Storage Research Center, Korea Institute of Energy Research, Daeduck Science Town, Taejon 305-343, Republic of Korea b Department of Chemistry, Vaish College, Rohtak 124001, India c Shenyang National Lab for Material Science, Institute of Metal Research, 72 Wenhua Road, Shenyang 110016, China |
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Abstract: | Nano-thin polypyrrole (PPy) layers with thickness from ∼5 nm to several 10s nm were deposited on 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 ∼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 ∼588 F g−1 at 30 mV s−1 and maintained as ∼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 ∼300 F g−1 at 200 mV s−1 in 6 M KOH. |
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Keywords: | Nano-thin polypyrrole layer Pseudo-capacitance Electric double layer capacitance Composite electrode Electrochemical capacitor Supercapacitor |
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