SUMMARYIn this study, ketjen black was used for polarized electrodes instead of conventionally employed acetylene black in order to improve the capacitance of an activated carbon-based electric double layer capacitor (EDLC). Usually, ketjen black exhibits higher electronic conductivity compared to acetylene black, so that ketjen black could be considered as a conducting fiber. Moreover, N 2 absorptiondesorption isotherm as well as TEM observation revealed that ketjen black used in this study has different types of pore structures compared to acetylene black. The capacitances of prepared EDLC were evaluated from discharge characteristics. It was found that the ketjen black containing EDLC showed fairly high capacitance compared to the one with acetylene black. In particular, an EDLC with 8 wt% ketjen black showed the highest capacitance among prepared samples. The specific capacitance of the best one was evaluated as 59.2 F/g. It was also found that the EDLC with 8 wt% ketjen black exhibited fairly stable capacitance at elevated temperatures based on the temperature dependence for capacitance in an EDLC with 10 wt% acetylene black and one with 8 wt% ketjen black.
In this work, carbonaceous materials were modified in order to improve capacitance and charge density in electric double layer capacitors (EDLCs). Optimal conditions for plasma surface treatment of activated carbon have been examined for times from 1 to 10 h at 150 °C. The plasma is a high-frequency glow discharge in N2. The pressure of the gas is 13.3 Pa. The electrode is set up so that the EDLC sample is covered with the glow discharge. Specific capacitance and charge density can be improved by plasma surface treatment of carbon materials.
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