• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.10-18
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• 2006

This article is concerned with the overview of the activated carbon fibers. Firstly, this review provides a comprehensive survey of the overall processes for the synthesis of the activated carbon fibers from the carbonaceous materials. Subsequently, the physicochemical properties such as pore structures and surface oxygen functional groups of the activated carbon fibers were discussed in detail. Finally, as electrochemical applications of the activated carbon fibers to electrode materials for electric double-layer capacitor (EDLC), the electrochemical characteristics of the activated carbon fiber electrodes and the various methods to improve the capacitance and rate capability were introduced. In particular, the effect of pore length distribution (PLD) on kinetics of double-layer charging/discharging was discussed based upon the experimental and theoretical results in our work. And then we discussed in detail the applications of the activated carbon fibers to adsorbent materials for purification of liquid and gas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1140-1143
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• 2002

This work describes the effect of conducting composite on the characteristics of electric double layer capacitor. The cell, which was fabricated with conducting composite consisted of 50 wt.% of SPB and 50 wt.% of VGCF, exhibits the higher specific capacitance, the lower resistance and the better rate capability than those of the cells fabricated with each single electronic conductor. These enhanced properties could be related with the dense structure of electrode.

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.8-8
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• 2005

• Carbon letters
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• v.6 no.2
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• pp.86-88
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• 2005

Mesoporous activated carbon (AC) was prepared from aged petroleum coke through chemical activation. The AC has a specific surface area of 1733 $m^2/g$ and a mean pore diameter of 2.37 nm. The volume fraction of 2 to 4nm pores is 56.74%. At a current density of 10 mA/$cm^2$, a specific capacitance of 240 F/g is achieved representing the use factor of the surface area of 69.2%. And the electrical double layer capacitor (EDLC) based on the AC shows an excellent power performance. This result suggests that the presence of high fraction of mesopores can effectively increase the adsorption efficiency of the specific surface area of the AC and enhance the power performance of EDLC based on the efficient surface area of the AC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1167-1171
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• 2006

This work describes the effect of binders, such as carboxymethylcellulose (CMC), CMC+ Polytetrafluoroethylene (PTFE) and PTFE, on the electrochemical and mechanical properties of activated carbon-electrode for electric double layer capacitor. The cell capacitors using the electrode bound with binary binder composed of CMC and PTFE, especially in composition CMC PTFE = 60 : 40 wt.%, has better rate capability and the lower internal resistance than those of the cell capacitor with CMC. On the other hand, the sheet type electrode kneaded with PTFE was bonded with conductive adhesive on Al foil. This cell capacitor using the electrode with PTFE exhibited the best mechanical properties and rate capability compared to the CMC and CMC+PTFE one. These behaviors could be explained by the well-developed network structure of PTFE fibrils doting the kneading process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.973-978
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• 2004

This work describes the effect of conducting materials on the electrochemical performances of electric double layer capacitor. Three kinds of Carbon black, such as Acethylene Black, Super P Black, Ketjen black supplied by Denki Kagaku Kogyo, MMM Carbon, Ketjen Black International Co. respectively, was added in carbon-Polytetrafluoroethylene (PTFE) electrode, which composition is activated carbon : carbon black : PTFE = 80 : 15 : 5 wt.%, and were compared with their electrochemical properties. The electrode with Ketjen Black has showed the lowest resistance than other carbon black, and also exhibited the better rate capability between 0.5 mA/cm$^2$ ∼ 100 mA/cm$^2$ current density in unit cell capacitor. On the other hand, as increasing the composition of Ketjen Black, the specific resistances of electrodes were decreased and Ketjen Black content higher than 15 wt% increased. The best rate capability was obtained at the electrode with 15 wt.% of Ketjen Black in unit cell capacitor. This behaviors would be correlated with the dense structure of electrode.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.101-107
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• 2009

This paper deal with development of on-line type voltage sag compensation system using supercapacitor EDLC to solve the voltage sag problems which are considered to be dominant disturbances affecting the power quality. With the wide use of semiconductor devices in electrical equipment, modem-type loads are becoming increasingly sensitive to the voltage sags and the disturbances prove to be costly to industries. Supercapacitor EDLC is employed to compensate dynamically for the voltage sag of system with sensitive loads. This capacitor has higher energy density than the electrolytic capacitor. Also, this capacitor has a lot of advantage such as no maintenance, longer life cycle and faster charge-discharge time than the battery system. Therefore, in this paper, the energy design scheme of supercapacitor and the configuration technique of on-line type voltage sag compensation systems are newly introduced. According to the results of experimental of prototype 5[kVA] system, it is verified that the developed system has effectiveness of voltage sag compensation by using a supercapacitor EDLC.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.252-256
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• 2007

A series of spherical porous carbons were prepared via resorcinol-formaldehyde (RF) sol-gel polymerization in the presence of cationic surfactant (CTAB, cetyltrimethylammonium bromide), wherein the carbon sphere size was controlled by varying the CTAB introduction time after a pre-determined period of addition reaction (termed as "pre-curing"). The sphere size gradually decreases with an increase in the pre-curing time within the range of 30-150 nm. The carbons possess two types of pores; one inside carbon spheres (intra-particle pores) and the other at the interstitial sites made by carbon spheres (inter-particle pores). Of the two, the surface exposed on the former was dominant to determine the electric double-layer capacitor (EDLC) performance of porous carbons. As the intra-particle pores were generated inside RF gel spheres by gasification, the pore diameter was similar for all these carbons, thereby the pore length turned out to be a decisive factor controlling the EDLC performance. The charge-discharge voltage profiles and complex capacitance analysis consistently illustrate that the smaller-sized RF carbons deliver a better rate capability, which must be the direct result of facilitated ion penetration into shorter pores.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.63-68
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• 2010

The $Li_4Ti_5O_{12}$/AC composite was prepared by sol-gel process with ultrasonication. The prepared composite was characterized by SEM, XRD and TG analysis, and their electrochemical behaviors were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge test in 1M $LiBF_4$/PC electrolyte. From the results, the $Li_4Ti_5O_{12}$ particles coated on AC surface had an average particle size of 100 nm and showed spinel-framework structure. When the potential range of the $Li_4Ti_5O_{12}$/AC composite was extended from 0.1 to 2.5 V, redox peaks and electric double layer property were revealed. The initial discharge capacity of $Li_4Ti_5O_{12}$/AC composite was 218 mAh $g^{-1}$ at 1 C. The enhancement of discharge capacity was attributed to electric double layer of added activated carbon.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.419-424
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• 2011

Carbon nanotubes (CNTs) were directly synthesized on a copper (Cu) plate as a current collector by the catalytic thermal vapor deposition method for an electric double-layer capacitor (EDLC) electrode. The diameters of vertically aligned CNTs grown on the Cu plate were 20~30 nm. From cyclic voltammetry (CV) results, the CNTs/Cu electrode showed high specific capacitance with typical profiles of EDLCs. Rectangularshaped CV curves suggested that the CNTs/Cu electrode could be an excellent candidate for an EDLC electrode. The specific capacitances were in a range of 25~75 F/g with a scan rate of 10~100 mV/s and KOH electrolyte concentration 1~6 M, and were maintained up to 1000 charge/discharge cycles due to strong adhesion between the Cu substrate and the CNTs.