• 제목/요약/키워드: Charge Transfer Resistance

검색결과 155건 처리시간 0.034초

Ni 및 Cu무전해 도금법에 의해 제조한 $LaNi_5$ 전극의 전기화학적 특성 (Electrochemical Characteristics of $LaNi_5$ Electrode Fabricated by Ni and Cu Electroless Plating Techniques)

  • 이수열;이재봉
    • 전기화학회지
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    • 제3권2호
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    • pp.121-126
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    • 2000
  • [ $AB_5$ ] 수소저장합금인 $LaNi_5$, 합금분말에 Ni 및 Cu 무전해 도금의 영향을 전기 화학적 실험을 통하여 고찰하였다. 전기 화학적 실험은 정전류 충$\cdot$방전 실험, 순환전류전위 실험, 교류 임피던스 실험 등을 실시하여 도금하지 않은 $LaNi_5$ 전극과 Ni 및 Cu 무전해 도금한 전극간의 특성을 비교 연구하였다. 현상학적인 분석으로는 SEM을 이용하여 분말상의 미세조직을 관찰하였으며 X-선 회절시험을 실시하였다 무전해 도금을 실시하여 Ni 및 Cu박막이 피복된 수소저장 합금은 활성화 특성파 싸이클 수명 등의 특성이 개선되었으며 도금하지 않은 전극에 비하여 반응속도가 증가하였다. 또한 충$\cdot$방전이 반복됨에 따라 전극과 전해질 계면에서의 전하이동저항이 현저하게 감소하였다. 따라서 본 연구에서 실시한 $LaNi_5$, 활물질에 Ni및 Cu 무전해 도금을 실시하면 초기 활성화반응을 촉진시키며 $LaNi_5$활물질이 전해질과의 직접 접촉을 피하게 되어 전극의 수명을 증가시키는 것을 알 수 있었다.

리튬 망간산화물 박막에서의 전극 반응의 개선 (Improvement of Electrochemical Reaction Kinetics in Lithium Manganese Oxide Thin Films)

  • 박영신;김찬수;주승기
    • 전기화학회지
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    • 제3권2호
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    • pp.96-99
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    • 2000
  • 리튬 망간 산화물 박막의 고율 방전 특성을 향상시키기 위하여 사진 식각 법을 이용하여 미세 패턴된 양극 박막을 제조하였다. 방전 전류 밀도를 달리하여 측정한 결과, 리튬 이온의 intercalations kinetic레 관계하는 전하 전달 저항 값이 감소하게 되어 고율 방전 특성이 향상되었다.

Supercapacitor용 활성탄 전극의 전기 화학적 특성 (Electrochemical Characteristics of Activated Carbon Electrode for Supercapacitor)

  • 김경민;이용욱;강안수
    • 대한안전경영과학회:학술대회논문집
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    • 대한안전경영과학회 2002년도 추계학술대회
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    • pp.273-277
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    • 2002
  • In the electrode fabrication of unit cell, we found that optimal the electrochemical characteristics were obtained with at 90 wt.% of activated carbon(BP-20), 5 wt.% of conducting agent(Ppy, Super P) and 5 wt.% of P(VdF-co-HFP)/PVP mixed binder. The electrochemical characteristics of unit cell with Ppy improver were as follows : 37.6 F/g of specific capacitance, 0.98 $\Omega$ of AC-ESR, 2.92 Wh/kg and 6.05 Wh/L of energy density, and 754 W/kg and 1,562 W/L of power density. It was confirmed that internal resistance were reduced due to the increase of electrical conductivity and filling density by the introduction of conductivity agent, and content of conducting agent was suitable in the range of 4~6 wt.%. According to the impedance measurement of the electrode with conductivity agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance(AC-ESR), fast charge transfer rate at interface between electrode and electrolyte, and low RC time constant.

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유기계 슈퍼커패시터에서 도전재의 양이 전기화학적 특성에 미치는 영향 (Effect of Conductive Additive Amount on Electrochemical Performances of Organic Supercapacitors)

  • 양인찬;이기훈;정지철
    • 한국재료학회지
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    • 제26권12호
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    • pp.696-703
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    • 2016
  • In this study, we intensively investigated the effect of conductive additive amount on electrochemical performance of organic supercapacitors. For this purpose, we assembled coin-type organic supercapacitor cells with a variation of conductive additive(carbon black) amount; carbon aerogel and polyvinylidene fluoride were employed as active material and binder, respectively. Carbon aerogel, which is a highly mesoporous and ultralight material, was prepared via pyrolysis of resorcinol-formaldehyde gels synthesized from polycondensation of two starting materials using sodium carbonate as the base catalyst. Successful formation of carbon aerogel was well confirmed by Fourier-transform infrared spectroscopy and $N_2$ adsorption-desorption analysis. Electrochemical performances of the assembled organic supercapacitor cells were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements. Amount of conductive additive was found to strongly affect the charge transfer resistance of the supercapacitor electrodes, leading to a different optimal amount of conductive additive in organic supercapacitor electrodes depending on the applied charge-discharge rate. A high-rate charge-discharge process required a relatively high amount of conductive additive. Through this work, we came to conclude that determining the optimal amount of conductive additive in developing an efficient organic supercapacitor should include a significant consideration of supercapacitor end use, especially the rate employed for the charge-discharge process.

충방전 온도에 따른 $LiM_{y}Mn_{2-y}O_{4}$정극 활물질의 임피던스 특성 분석 (The AC impedance of $LiM_{y}Mn_{2-y}O_{4}$cathode material by charge and discharge temperature)

  • 정인성;구할본
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2000년도 추계학술대회 논문집
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    • pp.351-354
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    • 2000
  • AC impedance of LiM $n_2$ $O_4$ and LiM $g_{0.1}$M $n_{1.9}$ $O_4$ samples have been studied at various temperature with charge-discharge test. AC impedance of LiM $n_2$ $O_4$ measured at -2$0^{\circ}C$, room temperature and 5$0^{\circ}C$ revealed that initial impedance before charge-discharge test was gradually decreased and become small by becoming law temperature. It indicates that the Li ion diffusion and the transfer resistance of the cathode are related to the temperature of cycling. Impedance at high temperature was suddenly increased because Mn dissolution and decomposition of electrolyte had been increased during cycling, compared to impedance at low temperature. Therefore, charge-discharge capacity was suddenly decreased at high but was slowly at low. In LiM $g_{0.1}$M $n_{1.9}$ $O_4$, impedance and capacity were stability at room temperature than there at 5$0^{\circ}C$, too. Initial impedance at 5$0^{\circ}C$ before charge-discharge test was small and impedance was suddenly increased during cycling than that at room temperature.ure.ure.

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겔식 납축 전지의 충전상태에 따른 임피던스 특성 연구 (Impedance Characteristics of the Gel Type VRLA Battery at the Various State-of-Charge)

  • 안상용;정의덕;원미숙;심윤보
    • 전기화학회지
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    • 제11권1호
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    • pp.33-36
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    • 2008
  • 본 연구에서는 겔식 VRLA (valve regulated lead acid번지의 충전상태(SoC) 판단을 위해 임피던스 기법을 이용하여 조사하였다. 임피던스는 VRLA전지 (2V/1.2Ah)의 다양한 충전상태에서 진폭 10mV로 100kHz에서${\sim}$10mHz까지 측정하였다. 측정된 임피던스 데이터로부터 등가회로를 유도하고, CNLS (Complex Non-linear Least Squares) 법을 사용하여 분석하였다. 양극 쪽의 전하전이 저항과 전기이중층 커패시턴스가 음극보다 높았다. 겔 저항은 충전상태가 감소함에 따라 증가하며 이는 VRLA 전지의 충전상태를 판단하는데 중요한 파라미터임을 확인하였다.

저온 폐열회수용 진동세관형 히트파이프 열교환기의 작동 유체에 따른 열전달 특성 (Influence of Working Fluids to Heat Transfer Characteristics of the Heat Exchanger using Oscillating Capillary Tube Heat Pipe for Low Temperature Waste Heat Recovery)

  • 이욱현;임용빈;김정훈;김종수
    • 설비공학논문집
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    • 제12권7호
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    • pp.659-666
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    • 2000
  • Heat transfer characteristics of a heat exchanger for low temperature waste heat recovery using oscillating capillary tube heat pipe were evaluated against the charge ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working fluids. The heat exchanger was composed of heat pipe with capillary tube bundles, having a 2.6mm in outer diameter, 1.4mm in inner diameter with 101m long, and 40 turns. Charge ratio of working fluid was 40% and 50%. Water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and9~27 kg /$m^2s$,, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-l42b and R-290 and it was proportional to Figure of merit for thermosyphons. As a result, it was thought that R-22 was the most suitable working fluid of waste heat recovery for low temperature waste heat recovery.

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PtCo/C 촉매를 사용한 PEMFC MEA의 활성화 프로토콜 비교 (The Comparison of Activation Protocols for PEMFC MEA with PtCo/C Catalyst)

  • 이기성;정현승;현진호;박찬호
    • 한국수소및신에너지학회논문집
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    • 제34권2호
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    • pp.178-186
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    • 2023
  • Three activation methods (constant voltage, current cycling, and hydrogen pumping) were applied to investigate the effects on the performance of the membrane electrode assembly (MEA) loaded with PtCo/C catalyst. The current cycling protocol took the shortest time to activate the MEA, while the performance after activation was the worst among the all activation methods. The constant voltage method took a moderate activation time and exhibited the best performance after activation. The hydrogen pumping protocol took the longest time to activate the MEA with moderate performance after activation. According to the distribution of relaxation time analysis, the improved performance after the activation mainly comes from the decrease of charge transfer resistance rather than the ionic resistance in the cathode catalyst layer, which suggests that the existence of water on the electrode is the key factor for activation.

Strain-Sensing Characteristics of Multi-Walled Carbon Nanotube Sheet

  • Jung, Daewoong;Lee, Gil S.
    • 센서학회지
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    • 제22권5호
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    • pp.315-320
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    • 2013
  • In this paper, the properties of strain sensors made of spin-capable multi-walled carbon nanotubes (MWCNTs) were characterized and their sensing mechanisms analyzed. The key contribution of this paper is a new fabrication technique that introduces a simpler transfer method compared to spin-coating or dispersion CNT. Resistance of the MWCNT sheet strain sensor increased linearly with higher strain. To investigate the effect of CNT concentration on sensitivity, two strain sensors with different layer numbers of MWCNT sheets (one and three layers) were fabricated. According to the results, the sensor with a three-layer sheet showed higher sensitivity than that with one layer. In addition, experiments were conducted to examine the effects of environmental factors, temperature, and gas on sensor sensitivity. An increase in temperature resulted in a reduction in sensor sensitivity. It was also observed that ambient gas influenced the properties of the MWCNT sheet due to charge transfer. Experimental results showed that there was a linear change in resistance in response to strain, and the resistance of the sensor fully recovered to its unstressed state and exhibited stable electromechanical properties.

염료감응형 태양전지의 $TiO_2$ Layer 다분할 효과에 따른 효율 향상 연구 (Improvement of Efficiency about $TiO_2$ Layer Multi-dividing Effect in Dye-sensitized Solar Cell)

  • 손민규;서현웅;이경준;홍지태;김희제
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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    • pp.425-427
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    • 2008
  • Active area of dye-sensitized solar cell (DSSC) has an effect on the efficiency of DSSC. As the active area increases, the efficiency goes down in a general way. This is caused by the increase of internal resistance in DSSC. The internal resistances are related to various resistant elements. The charge transfer processes at Pt counter electrode and the sheet resistance of TCO are two of these resistant elements. In this study, we try to divide the active area into several small sections in a large sized cell to reduce these two internal resistant elements. As a result, we find out that the fill factor is increased and then the conversion efficiency is improved as the number of dividing active area into several small sections is increased.

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