| Budget Amount *help |
¥3,710,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥210,000)
Fiscal Year 2007: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2006: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
In this work, it is first measured the spatio-temporal behavior of positive and negative charges in EDLC using the PEA method. At the same time, the capacitance obtained by the PEA method was compared with those obtained by the energy conversion method. As the results, in the case of using activated carbon which has 2000 m^2/g of specific surface area and 2.72 ran of average pore diameter as the materials of electrode for EDLC, negative charge density was about -173 C/m^2 and positive charge density was about 70.7 C/m^2. The result also showed that the distributions of positive/negative charges were spatially uneven and that the charge accumulation region concentrated on central part of the carbonaceous electrode of EDLC. The behavior of negative and positive charges measured by the PEA method reflected the hetero-charges distribution in EDLC. Additionally, ketjen black was used for polarized electrodes instead of conventionally used acetylene black in order to improve the capacitance
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of activated carbon-based EDLC. Usually, ketjen black exhibits higher conductivity compared with acetylene black, so that ketjen black could be considered as conducting filler. The capacitance of prepared EDLC was evaluated through discharge characteristics. It was found that the ketjen black containing EDLC showed very high capacitance compared to acetylene black one. Especially, 8 wt% ketjen black containing EDLC showed the highest capacitance among the prepared samples. The specific capacitance of the best one was evaluated as 59.2F/g. It was also found that the 8 wt% ketjen black containing EDLC exhibited very stable capacitance at elevated temperature from temperature dependence of capacitance for 10 wt% acetylene black containing EDLC and 8 wt% ketjen black one. Furthermore, carbonaceous materials were modified in order to improve capacitance and charge density in EDLC. Optimal conditions for plasma surface treatment of activated carbon have been examined for times from 10 min to 1 h at 150℃. The plasma source was a high-frequency glow discharge in N2. The operating gas pressure was 13.3 Pa. The electrode was set up so that the EDLC sample was covered with the glow discharge. As the results, space charge density was improved by the plasma surface treatment of carbon materials. Moreover, an activated carbon sheet was modified, to improve capacitance and energy density of EDLC. The plasma surface treatments were carried out for 1, 5, 10, 20, and 30 min. The plasma source was a DC glow discharge in argon gas. The pressure was 20 Pa and the distance between positive and negative electrodes was 20 mm. DC power was 70W. The activated carbon sheets were set up to cover the sheets with the DC glow discharge. As the results of plasma surface treatment, EDLC single cells with the activated carbon sheets became more marked at higher discharge rate because the BET surface area of activated carbon sheet increased with argon plasma etching. In addition, capacitance of EDLC single cells can be improved by the plasma surface treatment. Capacitance of the EDLC cells with the activated carbon sheets after 1 min plasma surface treatment was increased 2% compares to EDLC cells with the original activated carbon sheet at a high discharge rate. Less
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