Kenji Kurosawatsu

Plasma Surface Treatment of Carbonaceous Materials for Application in Electric Double Layer Capacitors

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.

Evaluation of quantity of stored charge in electric double layer capacitor by pulsed electro acoustic method

In this research, the space charge distribution in electric double layer capacitor (EDLC) for energy storage has been examined by a pulsed electro-acoustic (PEA) method. However, the measurement result has a reflection wave component generated by reflection and penetration of the acoustic wave, because the EDLC with five layer structures consists of three kind of materials (aluminum, cellulose, and activated carbon). Then, it is calculated from the acoustic impedance and relative permittivity of the material of EDLC, and examined the influence of reflected wave components on signal voltage. In this research, charge density influenced by reflection wave component from signal voltage was investigated. As a result, the correlation between signal voltage and charge density was understood, and the influence on charge distribution was examined.

Effect of Nitrogen Atom Doping for Electric Double Layer Capacitors Application

In this research, we measured spatio-temporal profiles of positive and negative charges in Electric Double Layer Capacitors (EDLCs) consist of activated carbon exposed to plasma discharge. The state of plasma is a high frequency glow discharge and sample of activated carbon is set on the center of glow discharge. Optimal conditions for plasma surface treatment of activated carbon have been examined with a time of 1~10 h at 150degC in N2. As the result, nitrogen atom is doped in the surface layer of the activated carbon, and capacitance of EDLCs has a peak in case of 1 h of plasma surface treatment. It is reported that capacitance increases with the nitrogen dope. Capacitance of EDLCs increased until 1 h of treatment time, but capacitance was decreasing in case of over 1 h of treatment time

Relation between Space Charge and Pore Size of Nano Porous Electrode for Super Capacitor

The space charge distribution in electric double layer capacitor (EDLC) for energy storage has been examined by pulsed electro-acoustic (PEA) method since 2002. It is found that the measuremental result can be influenced by the reflection and penetration of the sound wave when the space charge distribution of EDLC is measured by PEA method, because the EDLC has a five layer structure consisting of three materials (aluminum, cellulose, and activated carbon). Then, we calculated reflection wave components that influence on charge density from the acoustic impedance and relative permittivity of the materials. As a result, it has been understood that the changes in the space charge distribution of EDLC and the charge characteristic of the EDLC are almost corresponding. The use of the PEA method can be expected as a method of evaluating the accumulation charge of EDLC by measuring the space charge distribution of it. In this paper, a polarized electrode is made to develop EDLC and a ratio of surface area and average pore diameter of polarized electrode is measured by nitrogen adsorption method at 77K. Also, relation between a ratio of surface area and average pore diameter and space charge distributions of EDLC are discussed.