• 대한전기학회논문지
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• 제40권9호
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• pp.883-892
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• 1991

This paper presnets the characteristics of electropolymerization and electrochemicla propoerties of polyaniline(PAn). From the morphology study on the PAn surface, it seems that coagulation of the fibrils on the surface proceeds as the PAn grows, resulting in fibril clusters with new branches and more extensive voids. While PAn/Li cell is cycled at potential range between 2.9V and 3.7V in which the first strong reduction peak of 2.75V does not appear, its oxidation reduction capacities were increased up to about tenth cycle. Electricity efficiency of stable charge-discharge to deep discharge in PAn/Li cell was 42.9%. Average charge potential, avergae discharge potential, energy density, and charge-discharge energy efficiency of the PAn/Li cell were 3.4V, 3.25V, 132.9Wh/kg, and 95.6%, respectively.

• Carbon letters
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• 제5권3호
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• pp.118-126
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• 2004

MCMB (Mesocarbon microbeads) is a kind of anode material for lithium-ion secondary battery. MCMB charge/discharge cycle stability is one of the important criterion at lithium-ion battery operation. In this study, the cycling stability of a lithium-ion secondary battery has been examined. MCMB was made by the direct solvent extraction method. After the MCMB was carbonized and graphitized, the measurement of charge/discharge capacity and efficiency were carried out. In the result, discharge capacity of MCMB in the initial cycle was above 290.0 mAh/g. After the second cycle, efficiency of charge/discharge MCMB was about 98%. These results were similar to the commercial MCMB product.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.163.2-163.2
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• 2010

In this work, nano-flake shaped nickel oxide (NiO) films were synthesized by chemical bath deposition technique for electrochemical capacitors. The deposition was carried out for 1 and 2 h at room temperature using nickel foam as the substrate and the current collector. The structure and morphology of prepared NiO film were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). And, electrochemical properties were characterized by cyclic voltammetry, galvanostatic charge-discharge, and AC impedence measurement. It was found that the NiO film was constructed by many interconnected NiO nano-flakes which arranged vertically to the substrate, forming a net-like structure with large pores. The open macropores may facilitate the electrolyte penetration and ion migration, resulted in the utilization of nickel oxide due to the increased surface area for electrochemical reactions. Furthermore, it was found that the deposition onto nickel foam as substrate and curent collector led to decrease of the ion transfer resistance so that its specific capacitance of a NiO film had high value than NiO nano flake powder.

• Journal of Electrochemical Science and Technology
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• 제8권4호
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• pp.314-322
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• 2017

The electrolyte plays one of the most significant roles in the performance of electrochemical supercapacitors. Most liquid organic electrolytes used commercially have temperature and potential range constraints, which limit the possible energy and power output of the supercapacitor. The effect of elevated temperature on a lithium bis(oxalate)borate(LiBOB) salt-based electrolyte was evaluated in a symmetric supercapacitor assembled with activated carbon electrodes and different electrolyte blends of acetonitrile(ACN) and propylene carbonate(PC). The electrochemical properties were investigated using linear sweep voltammetry, cyclic voltammetry, galvanostatic charge-discharge cycles, and electrochemical impedance spectroscopy. In particular, it was shown that LiBOB is stable at an operational temperature of $80^{\circ}C$, and that, blending the solvents helps to improve the overall performance of the supercapacitor. The cells retained about 81% of the initial specific capacitance after 1000 galvanic cycles in the potential range of 0-2.5 V. Thus, LiBOB/ACN:PC electrolytes exhibit a promising role in supercapacitor applications under elevated temperature conditions.

• 전기화학회지
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• 제6권2호
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• pp.153-157
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• 2003

전기이중층 축전용량(electric double layer capacitance)과 유사축전용량(pseudo-capacitance)을 함께 갖는 하이브리드 전기화학 축전기에 대한 연구를 수행하였다. 양극은 $Ni(OH)_2$ 활성탄소가 복합된 전극을 사용하였으며 음극은 활성탄소를 활물질로 사용하므로써 비대칭 전극 구조를 갖는다. 셀 실험을 위하여 $5\times5cm^2$ 크기인 전극을 제작 사용하였다. Cyclic voltammetry측정 및 교류 임피던스 측정실험을 통하여 각각의 셀들이 갖는 전기화학적 거동을 조사하였고 충 방전 실험을 통하여 양극과 음극의 최적 질량비를 조사하였다.

• 전기화학회지
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• 제6권2호
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• pp.98-102
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• 2003

Urethane acrylate oligomer was synthesized and used in a gel polymer electrolyte (GPE) and then its electrochemical performances were evaluated. $LiCoO_2/GPE/graphite$ cells were prepared and their performances depending on discharge currents and temperatures were evaluated. The precursor containing $5 vol\%$ curable mixture had a low viscosity relatively. ionic conductivity of the gel polymer electrolyte at room temperature and $-20^{\circ}C$ was ca. $5.9\times10^{-3}S{\cdot}cm^{-1}\;and\;1.4times10^{-3}S{\cdot}cm^{-1}$, respectively. GPE showed good electrochemical stability up to potential of 4.5V vs. RLi/Li^+.\;LiCoO_2/GPE/graphite$ cell showed a good high-rate and low-temperature performance.

• 전기화학회지
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• 제16권2호
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• pp.65-69
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• 2013

전기이중층 커패시터용 활성탄의 정전 용량 향상을 위해 우레아를 이용해 활성탄 표면에 펩티드 결합을 유도하였다. 우레아 도입에 따른 활성탄은 소성과정을 거쳐 안정화되었으며, 전기화학적 특성을 순환전류 전압법을 이용하여 정전 용량을 관찰하고, 임피던스를 통해 저항 변화를 관찰하였으며, 충방전 평가를 통해 싸이클 성능을 관찰하였다. 결과적으로 질소성 작용기의 도입으로 정전 용량은 기존 탄소재에 비해 약 22.9%의 향상을 이루었으며, 저항 감소 및 우수한 싸이클 성능을 나타냄을 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제5권4호
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• pp.109-114
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• 2014

The $Li_3V_2(PO_4)_3$/graphene nano-particles composite was successfully synthesized by a facile sol-gel method. The addition of a graphene in $Li_3V_2(PO_4)_3(LVP)$(LVP) showed the high crystallinity and influenced the morphology of the $Li_3V_2(PO_4)_3$ particles observed in X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LVP/graphene samples were well connected, resulting in fast charge transfer. The effect of the addition graphene nano-particles on electrochemical performance of the materials was investigated. Compared with the pristine LVP, the LVP/graphene composite delivered a higher discharge capacity of $122mAh\;g^{-1}$ at 0.1 C-rate, better rate capability and cyclability in the potential range of 3.0-4.3 V. The electrochemical impedance spectra (EIS) measurement showed the improved electronic conductivity for the LVP/graphene composite, which can ensure the high specific capacity and rate capability.

• 전기화학회지
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• 제13권2호
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• pp.110-115
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• 2010

The plasticized polymer electrolytes based on polyvinylidene fluoride-co-hexafluoropropylene (P(VdF-co-HFP)), tetra (ethylene glycol) dimethyl ether (TEGDME), and lithium perchlorate ($LiClO_4$) are prepared for the lithium sulfur batteries by solution casting with a doctor-blade. The polymer electrolyte with EO : Li ratio of 16 : 1 shows the maximum ionic conductivity, $6.5\;{\times}\;10^{-4}\;S/cm$ at room temperature. To understand the effect of the salt concentration on the electrochemical performance, the polymer electrolytes are characterized using electrochemical impedance spectroscopy (EIS), infrared spectroscopy (IR), viscometer, and differential scanning calorimeter (DSC). The optimum concentration and mobility of the charge carriers could lead to enhance the utilization of sulfur active materials and the cyclability of the Li/S unit cell.

• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.180-185
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• 2011

The layered lithium-manganese oxide ($Li_2MnO_3$) as a cathode material of lithium ion secondary batteries was prepared and characterized the physico-chemical and electrochemical properties. The morphological and structural changes of MnO(OH) and $Li_2MnO_3$ are closely connected to the changes of electrochemical properties. The crystallinity of $Li_2MnO_3$ is enhanced as the annealing temperature increase, but its capacity is reduced due to the easier structural changes of less crystalline $Li_2MnO_3$ than highly crystalline one. Moreover, the addition of buffer material such as MnO(OH) into cathode causes to reduce the morphological and structural changes of layered $Li_2MnO_3$ and increase the discharge capacity and cycleability.