• 대한안전경영과학회지
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• 제2권2호
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• pp.95-108
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• 2000

Electrochemical charateristics of activated carbon fiber cloth(ACFC) electrode were studied with propylene carbonate(PC), ${\gamma}$-butyrolactone(GBL) and N,N-dimethyl-formamide(DMF) as a solvent and tetraethylammoniumtetrafluoroborate(TEABF$_4$), tetraethylammoniumhexafluorophosphate(TEABF$_{6}$), tetrabutylammoniumtetrafluoroborate(TBABF$_4$) and tetrabutylammonium hexafluorophosphate(TBAPF$_6$) as an electrolytes(active material). The concentrations of electrolytes were in the range of 0.2~1.2 N, the volume ratios of PC and DMF as a mixed solvent system, were 90：10, 80：20, 70：30, 60：40, 50：50, and 40：60 vol%. Electrochemical characteristics such as electric conductivity, internal resistance, and electric capacitance of fabricated unit cells were measured after the moisture of activated material was removed with molecular sieve. Electrochemical characteristics were better in mixed solvents system than in mono solvent system. The mono solvent system of 1.0 N electrolyte of GBL/TEABF$_4$ with activated carbon cloth electrodes showed better result but the mixed solvent system with PC and DMF/TEABF$_4$(50：50 vol%) and the concentration of 1.0 N electrolyte showed the best characteristics. Internal resistance was 3.47 $\Omega$ and specific capacitance was 19.1 F/g respectively.y.

• 공업화학
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• 제18권3호
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• pp.291-295
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• 2007

전기화학적으로 용량이 큰 활물질을 얻기 위한 수단으로 니들 코크스를 $NaClO_3$과 70 wt%의 $HNO_3$으로 구성된 수용액을 이용하여 산화처리를 하였다. $NaClO_3$/니들 코크스의 질량비가 7.5배인 수용액에서 산화 처리한 결과, 니들 코크스는 산화흑연 구조로 상변이가 일어나고, 또한 산소의 함유량의 증가와 함께 층간거리는 $6.9{\AA}$으로 확대되었다. 한편, 산화 니들 코크스의 전기이중층 커패시터용 분극 전극으로서의 전기화학적 특성은 acetonitrile의 용매에 각각 1.2 M의 TEABF4 (tetraethylammonium tetrafluoroborate)와 $TEABF_4$ (triethylmethylammonium tetrafluoroborate)의 전해질이 함유된 유기용액을 각각 사용하여 조사하였다. 1.2 M $TEABF_4$/acetonitrile의 전해액을 사용한 커패시터 셀은 1.2 M $TEABF_4$/acetonitrile의 전해액을 사용한 커패시터 셀에 비해 전극저항은 $0.05{\Omega}$로 낮았고, 2 전극 기준으로 0~2.5 V에서 측정한 용량 및 부피 당 용량은 32.0 F/g와 25.5 F/mL으로 높은 수치를 나타내었다. 이러한 전기화학적 거동을 천연흑연 구조에서의 층간 거리와 전해질의 양이온 크기와의 상관관계로 논의하였다.

• 전기화학회지
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• 제4권3호
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• pp.98-103
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• 2001

EDLC(electric double layer capacitor)용 활성탄소전극의 제조공정을 dip coating method, doctor blade coating method, paste rolling method로 달리하여 전기화학적 특성과 비축전 용량을 조사하였다. Dip coating method에 의한 전극제조시 전해질염으로 LiPF6를 이용하고 유기용매로 PC-DEC를 이용한 EDLC의 비축전 용량이 130F/g으로 가장 우수하였고, 선형의 시간전압곡선에서의 IR-drop도 0.11V로 작았으며 CV(cyclic voltammetry) 분석 또한 이상적인 EDLC의 특성을 나타내었다.

• 한국재료학회지
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• 제19권10호
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• pp.544-549
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• 2009

Activated carbon (AC) with very large surface area has high capacitance per weight. However, such activation methods tend to suffer from low yields, below 50%, and are low in electrode density and capacitance per volume. Carbon NanoFibers (CNFs) had high surface area polarizability, high electrical conductivity and chemical stability, as well as extremely high mechanical strength and modulus, which make them an important material for electrochemical capacitors. The electrochemical properties of immobilized CNF electrodes were studied for use as in electrical double layer capacitor (EDLC) applications. Immobilized CNFs on Ni foam grown by thermal chemical vapor deposition (CVD) were successfully fabricated. CNFs had a uniform diameter range from 50 to 60 nm. Surface area was 56 m$^2$/g. CNF electrodes were compared with AC and multi wall carbon nanotube (MWNT) electrodes. The electrochemical performance of the various electrodes was examined with aqueous electrolyte of 2M KOH. Equivalent series resistance (ESR) of the CNF electrodes was lower than that of AC and MWNT electrodes. The specific capacitance of 47.5 F/g of the CNF electrodes was achieved with discharge current density of 1 mA/cm$^2$.

• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.152-156
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• 2011

A hybrid supercapacitor is fabricated using a composite material from $LiMn_2O_4$ (LMO) and activated carbon (AC) as the positive electrode and AC as the negative electrode to form the (LMO + AC)/AC system. Volume ratio (positive : negative) of electrodes is controlled to investigate of the power and energy balance. The (LMO + AC)/AC system shows better performances than the LMO/AC system. Especially, electrochemical impedance spectra, rate charge.discharge and cycle performance testing show that the (LMO + AC)/AC system have an outstanding electrochemical performance at volume ratios of (LMO + AC)/AC = 1 : 1.7 and 1 : 2. Electric double layer capacitor (EDLC) capacitance between AC of the positive electrode and AC of the negative electrode improves power density without loss of capacitance. Stable capacitance is achieved by lowering the positive electrode resistance and balancing the energy and power densities between the positive and negative electrodes by the addition of AC to the positive electrode at high current density.

• Carbon letters
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• 제12권4호
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• pp.252-255
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• 2011

Carbon-based electric double-layer capacitors are being evaluated as potential energy-storage devices in an expanding number of applications. In this study, samples of carbon black (CB) treated at different temperatures ranging from $650^{\circ}C$ to $1100^{\circ}C$ were used as electrodes to improve the efficiency of a capacitor. The surface properties of the heat-treated CB samples were characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The effect of the heat-treatment temperature on the electrochemical behaviors was investigated by cyclic voltammetry and in galvanostatic charge-discharge experiments. The experimental results showed that the crystallinity of the CBs increased as the heat-treatment temperature increased. In addition, the specific capacitance of the CBs was found to increase with the increase in the heat-treatment temperature. The maximum specific capacitance was 165 $F{\cdot}g-1$ for the CB sample treated at $1000^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3183-3189
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• 2010

In order to increase the specific capacitance and energy density of supercapacitors, non-aqueous supercapacitors were prepared using lithium transition-metal oxides and activated carbons as active materials. The electrochemical properties were analyzed in terms of the content of lithium transition-metal oxides. The results of cyclic voltammetry and AC-impedance analyses showed that the pseudocapacitance may stem from the synergistic contributions of capacitive and faradic effects; the former is due to the electric double layer which is prepared in the interface of activated carbon and organic electrolyte, and the latter is due to the intercalation of lithium ($Li^+$) ions. The specific capacitance and energy density of a supercapacitor improved as the lithium transition-metal oxides content increased, showing 60% increase compared to those of supercapacitor using a pure activated carbon positive electrode.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.69.3-69.3
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• 2012

A high-performance low-voltage graphene field-effect transistor (FED array was fabricated on a flexible polymer substrate using solution-processable, high-capacitance ion gel gate dielectrics. The high capacitance of the ion gel, which originated from the formation of an electric double layer under the application of a gate voltage, yielded a high on-current and low voltage operation below 3 V. The graphene FETs fabricated on the plastic substrates showed a hole and electron mobility of 203 and 91 $cm^2/Vs$, respectively, at a drain bias of - I V. Moreover, ion gel gated graphene FETs on the plastic substrates exhibited remarkably good mechanical flexibility. This method represents a significant step in the application of graphene to flexible and stretchable electronics.

• 공업화학
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• 제28권6호
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• pp.638-644
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• 2017

전기이중층 커패시터(electric double layer capacitor, EDLC) 전극용 핏치계 활성탄소섬유의 고출력 특성을 향상시키기 위하여 불소와 산소 혼합가스의 다양한 불소분압에 따라 함산소불소화 표면처리를 수행하였다. 함산소불소화 처리된 핏치계 활성탄소섬유는 불소 부분압이 증가함에 따라 선형적인 불소관능기의 증가를 보였고, 산소관능기는 증가하였으나 부분압에 따라 차이가 없었다. 또한 함산소불소화를 통하여 활성탄소섬유 표면의 식각 반응으로 인하여 비표면적 및 기공부피는 감소하였으나 중간기공 부피는 약 4.5배 증가하였다. 50%의 불소가스 분압으로 처리한 활성탄소섬유의 경우 5와 50 mV/s의 전압주입속도에서 비정전용량이 약 29%와 61%로 증가함을 확인하였다. 이러한 비정전용량의 향상은 함산소불소화 처리를 통한 활성탄소섬유 표면의 산소 및 불소 관능기의 도입과 중간기공의 증가에 의한 효과로 사료된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.683-686
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• 2004

In recent years, the supercapacitor and hybrid capacitor have related with substitutional energy source focused of many scientists because of their usage in power sources for electric vehicles, computers and other electric devices. The storage energy of electrical charge is based on electrostatic interactions in the electric double layer at the electrode/electrolyte interface, resulting in high rate capability and long cycle performance compared with batteries based on Faradaic electrode reactions. So we have been considered to carbon nanofibers as the ideal material for supercapacitors due to their high utilization of specific surface area, good conductivity, chemical stability and other advantages. In this work, we aimed to find out that the capacitance have increased because of electrochemical capacitance to provide by carbon nanofibers. Also carbon nanofibers based on chemical method and water treatment have been resulted larger capacitances and also exhibit better electrochemical behaviors about 15% than before of nontreated state. And also optical observations with treated and nontrteated carbon nanofibers discussed by the TEM, SEM, EDX, BET works and specific surface area analyzer. Their results also focused on the surface area of electrode and electrical capacitance was also improved by the effect of surface treatments.