Activated carbon fiber cloth (ACFC) electrodes whose surface was modified by "pulsed cold plasma", i.e., low-temperature plasma generated by a pulsed electric power in argon-oxygen mixed gas at a reduced pressure, were applied to electric double layer (EDL) capacitors with an organic electrolyte composed of propylene carbonate and tetraethylammonium tetrafluoroborate (TEABF_4). The treatgment of the ACFC electrodes with the pulsed cold plasma increased toal capacitance in the EDL capacitors. The observed increase in the total capaccitance was ascribed mainly to an ascertained increase in capacitance of a negative ACFC electrode involving TEA~+ cation adsorption/desorption with the cold plasma treatment. No obvious increase in capacitance of a positive ACFC electrode involving BF_4~- anion adsorption/desorption was observed with the plasma treatment. The chemical and electrochemical characteristics of a treated ACFC interface were found to be favorable for TEA~+ cation adsportion/desorption.
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