Mitsufumi Taniguchi

Temperature dependence of capacitance in electrochemical super capacitor

In this study, ketjen black was used for polarized electrodes instead of conventionally used acetylene black in order to improve the capacitance of 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 conducting filler. Moreover, N2 adsorption-desorption isotherm as well as TEM observation revealed that ketjen black used in this study has different type 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 acetylene black containing one. In addition, in a temperature characteristic of EDLC which made ketjen black and acetylene black with quantity of same combination, we understood that ketjen black was superior to acetylene black. This experiment was done 50degC from 0degC in a temperature range. Ketjen black was superior to acetylene black in all temperature. It is understood that capacitance of EDLC was increased by using ketjen black.

Thickness dependence of carbon electrode on space charge of electric double layer capacitor

The space charge distribution in an Electric Double Layer Capacitor (EDLC) for energy storage has been examined by a Pulsed Electro-Acoustic (PEA) method. The EDLC in this experiment consists of aluminum as a current collector with the thickness of 30 mum, cellulose as a separator with the thickness of 20 mum, activated carbon sheet as a polarized electrode. Each component has section area of 30x30 mm2. The organic electrolyte was a mixed solution of propylene carbonate (C4H5O3) and tetra ethyl ammonium tetra fluoro borate (C2Hs)4NBF4 in the molar ratio of 1:0.8. The dc voltage of 2.5 V, for electrical charge formation, was applied to the EDLC sample. In this research, thickness of activated carbon sheet was changed from 150 mum to 300 mum to observe the state of space charge in polarized electrode. Space charge distributions of EDLC were measured and maximum charge density and cumulative charge density on various thickness of polarized electrode were investigated. As the results, it can be found that the maximum charge density was high in case of thin polarized electrode and cumulative charge density was great in case of thick polarized electrode. Therefore, activated carbon sheet that thickness is thin is effective for development of high power density type EDLC, which has rapid charge and discharge performance. Also, activated carbon sheet that thickness is thick is effective for development of high energy density type EDLC, which has long time charge and discharge.

Influence on capacitance of EDLC by a functional group of a conductive material

In this research, high-capacity once electric double layer capacitor (EDLC) was targeted, influence on capacitance by quantity of functional group of Ketjen black as the conductive materials of the polarized electrode was examined. Existence of an oxygen functional group on the surface of carbon electrode in EDLC is connected to capacitance increasing with faraday reaction and improvement of wettability of a water solution electrolyte to an electrode[1]. Therefore, the EDLC was evaluated with different Ketjen black of quantity of functional group. As the result, wettability of a water solution electrolyte to an electrode was improved by increase of a functional group, and osmosis of an ion became good, and the capacitance was increased. In addition, an ion was adsorbed at the deep of a pore by the removal of a functional group, and capacitance was increased.

Capacitance behavior of electric double layer capacitor using nanocomposite electrode

In this study, capacitance behavior of Electric Double Layer Capacitor (EDLC) with nanocomposite electrode for energy storage has been examined by charge-discharge characteristics. Also, internal resistance of EDLC was evaluated using two kinds of conducting filler. The one is acetylene black (AB) and the other is Ketjenblack (KB). KB was used for polarized electrodes instead of conventionally used AB in order to improve the capacitance and to decrease the internal resistance of EDLC. Usually, KB exhibits higher electronic conductivity compared to AB, and KB could be considered as conducting filler. The temperature dependence of capacitance and internal resistance of prepared EDLC using aqueous electrolyte, organic electrolyte and 2 kinds of ionic liquid was evaluated. Also, adsorbed ion numbers on the surface of KB and pore utilization of KB on each electrolyte was evaluated. As the results, it was found that the KB containing EDLC showed fairly high capacitance compared to AB containing one on all electrolyte. In addition, temperature dependence of EDLC containing KB and AB were measured on temperature from 0 °C to 50 °C. It was understood that KB was superior to AB in all temperature and all electrolyte on capacitance and internal resistance. Moreover, adsorbed ion numbers on the surface of KB and pore utilization of KB was high using aqueous electrolyte.

Evaluation of Space Charge and Capacitance of Electric Double Layer Capacitor using Ionic Liquid

In this study, space charge distribution in Electric Double Layer Capacitor (EDLC) for energy storage has been examined by Pulsed Electro-Acoustic (PEA) Method. Also, ketjen black was used for polarized electrodes instead of conventionally used acetylene black in order to improve the capacitance of EDLC. Usually, ketjen black exhibits higher electronic conductivity compared to acetylene black, so that ketjen black could be considered as conducting filler. Moreover, N2 adsorption-desorption isotherm as well as TEM observation revealed that ketjen black used in this study has different type of pore structures compared to acetylene black. Therefore, the space charge and capacitance of prepared EDLC using ionic liquid was evaluated. As the results, it was found that the ketjen black containing EDLC showed fairly high charge density and high capacitance compared to acetylene black containing one. In addition, temperature characteristic of EDLC containing ketjen black and acetylene black with best quantity were measured on temperature from 0degC to 50degC. It is understood that ketjen black as conducting material and ionic liquid based EDLC was superior to organic electrolyte based EDLC in all temperature on capacitance. Also, internal resistance of EDLC containing ketjen black and ionic liquid based EDLC can be decrease.