• Title, Summary, Keyword: Coin-type Cell

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Effect of Electrolyte Amounts on Electrochemical Properties of Coin-Type Lithium-Ion Cells (액체전해액의 함량에 따른 리튬이온전지 코인셀의 전기화학적 특성 연구)

  • Yoon, Byeolhee;Han, Taeyeong;Kim, Seokwoo;Jin, Dahee;Lee, Yong min;Ryou, Myung-Hyun
    • Journal of the Korean Electrochemical Society
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    • v.21 no.2
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    • pp.39-46
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    • 2018
  • Many studies on the electrochemical performance of Li secondary batteries have been obtained using coin-type cells due to the ease of assembly, low cost and ensuring reproducibility. The coin-type cell consists of a case, a gasket, a spacer disk, and a wave spring. These structural features require a greater amount of liquid electrolyte to assemble than other types of cells such as laminated cells and cylindrical cells. Nevertheless, little research has been conducted on the effect of excess liquid electrolytes on the electrochemical performances of Li secondary batteries. In this study, we investigate the effect of different amounts of electrolyte on the coin-type cells. The amount of electrolytes is adjusted to 30 and $100mg\;mAh^{-1}$. Cycle performances at room temperature ($25^{\circ}C$) and high temperature ($60^{\circ}C$) and high voltage are performed to investigate the electrochemical properties of the different amount of electrolytes. In the case of the unit cell including the electrolyte of $30mg\;mAh^{-1}$, the discharging capacity retention characteristic is excellent in comparison with the case of $100mg\;mAh^{-1}$ under the high temperature and high voltage condition. The former shows a larger increase in internal resistance than the latter, confirming that the amount of electrolyte significantly influences the discharge capacity retention characteristics of the battery.

Fabrication Characteristics and Performance Evaluation of a Large Unit Cell for Solid Oxide Fuel Cell (고체산화물연료전지용 대면적 단위전지 제조특성 및 성능평가)

  • Shin, Y.C.;Kim, Y.M.;Oh, I.H.;Kim, H.S.;Lee, M.S.;Hyun, S.H.
    • 한국신재생에너지학회:학술대회논문집
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    • pp.13-16
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    • 2008
  • Solid oxide fuel cell(SOFC) is an electrochemical energy conversion system with high efficiency and low-emission of pollution. In order to reduce the operating temperature of SOFC system under $800^{\circ}C$, the thickness reduction of YSZ electrolyte to be as thin as possible, e.g., less than 10 ${\mu}m$ are considered with the microstructure control and optimum design of unit cell. Methods for reducing the thickness of YSZ electrolyte have been investigated in coin cell. Moreover, a large unit cell($8cm{\times}8cm$) for SOFC was fabricated using an anode-supported electrolyte assembly with a thinner electrolyte layer, which was prepared by a tape casting method with a co-sintering technique. we studied the design factors such as active layer, electrolyte thickness, cathode composition, etc,. by the coin type of unit cell ahead of the fabrication process of a large unit cell and also reviewed about the evaluation technique of a large size unit cell such as interconnect design, sealing materials and current collector and so forth. Electrochemical evaluations of the unit cells, including measurements such as power density and impedance, were performed and analyzed. Maximum power density and polarization impedance of coin cell were 0.34W/$cm^2$ and $0.45{\Omega}cm^2$ at $800^{\circ}C$, respectively. However, Maxium power density of a large unit cell($5cm{\times}5cm$) decreased to 0.21W/$cm^2$ at $800^{\circ}C$ due to the increase of ohmic resistance. However, It was found that the potential value of a large unit cell loaded by 0.22A/$cm^2$ showed 0.76V at 100hrs without the degradation of unit cell.

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Synthesis and Electrochemical Characteristics of Carbon added Li3V2(PO4)3 (탄소첨가한 Li3V2(PO4)3의 합성 및 전기화학적 특성)

  • Jo, Yeong-Im;Na, Byung-Ki
    • Journal of the Korean Electrochemical Society
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    • v.15 no.2
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    • pp.101-108
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    • 2012
  • The purpose of this study was to improve the conductivity of $Li_3V_2(PO_4){_3}$ by adding carbon source so that the discharge rate and cyclic properties were improved. Glucose and CNT were added to $Li_3V_2(PO_4){_3}$ and the structure and electrochemical properties were studied. $Li_3V_2(PO_4){_3}$, $Li_3V_2(PO_4){_3}$/C and $Li_3V_2(PO_4){_3}$/CNT were synthesised by solid state reaction using hydrogen reduction method at 600, 700, 800, $900^{\circ}C$. The cathode materials were assembled to coin cell type 2032 with Lithium metal as a counter electrode. The coin cell was galvanostatically evaluated in the voltage range of 3.0~4.8 V.

Electrochemical Performance of Hybrid (Activated Carbon+LiCoO2) Electrode (하이브리드 (활성탄소+LiCoO2) 전극의 전기화학적 특성)

  • Kim, Ick-Jun;Jeon, Min-Je;Yang, Sun-Hye;Kim, Hyun-Soo;Moon, Sung-In;Oh, Dae-Hee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.9
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    • pp.849-854
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    • 2006
  • In this study, the hybrid electrodes, composed of the activated carbon powders and $LiCoO_{2}$ powders, were prepared as a cathode for the high-capacitance type hybrid capacitor, and the electrochemical properties of the hybrid electrodes were examined in terms of the weight composition and the milling time of $LiCoO_{2}$ powders. The specific volumetric capacities were increased with increasing of the composition of $LiCoO_{2}$ powders in the hybrid electrodes. On the other hand the coin cell capacitors, using the hybrid electrodes with $LiCoO_{2}$ poweders milled for 200 h, have exhibited the lower internal resistivities and the better capacity retention after 100 charge-discharge cycle than those of the coin cell capacitors using the hybrid electrodes with raw $LiCoO_{2}$ powders.

Performance Analysis with Various Amounts of Electrolyte in a Molten Carbonate Fuel Cell

  • Kim, Yu-Jeong;Kim, Tae-Kyun;Lee, Ki-Jeong;Lee, Choong-Gon
    • Journal of Electrochemical Science and Technology
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    • v.7 no.3
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    • pp.234-240
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    • 2016
  • The effect of initial electrolyte loading (IEL) on cell performance in a coin-type molten carbonate fuel cell (MCFC) was investigated in this work. Since the material of MCFC depends on the manufacturer, optimisation requires experimental investigation. In total, four IEL values, 1.5, 2.0, 3.0, and 4.0 g, were used, corresponding to a pore filling ratio (PFR) of 38, 51, 77, and 102%, respectively. The cell performance with respect to the PFR was analysed via steady-state polarisation, step-chronopotentiomtery, and impedance methods. The electrochemical analyses revealed that internal resistance and overpotential of the cell decreased with increasing PFR, and a large overpotential was observed when the PFR was 102%, probably due to the flooding phenomenon. After operation, cross-section of the cell was analysed via surface analysis of SEM and EDS methods, and the remaining electrolyte was estimated by dissolution of the cell in 10 wt% acetic acid. A linear relationship between IEL and the weight reduction ratio by dissolution was obtained. Thus, the remaining amount of electrolyte could be measured after operation. The results of SEM and EDS showed that a PFR of 38 and 102% showed a lack and flooding of electrolytes at the cell, respectively, which led to a large overpotential. This work reports that MCFC performance is allowed only in the narrow range of PFR.

Analysis of Cell Performance with Varied Electrolyte Species and Amounts in a Molten Carbonate Fuel Cell

  • Lee, Ki-Jeong;Kim, Yu-Jeong;Koomson, Samuel;Lee, Choong-Gon
    • Journal of Electrochemical Science and Technology
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    • v.9 no.2
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    • pp.141-148
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    • 2018
  • This study evaluated the performance characteristics of varied electrolyte species and amounts in a molten carbonate fuel cell (MCFC). Coin-type MCFCs were used at the condition of $650^{\circ}C$ and 1 atm. In order to measure the effects of varied electrolyte species and amounts, electrolytes of $(Li+K)_2CO_3$ and $(Li+Na)_2CO_3$ were selected and the amounts of 1.5 g, 2.0 g, 3.0 g, and 4.0 g were used. Insignificant performance differences were observed in the cell using different electrolytes, but the cell performance was sensitive to the amount of the electrolyte used. The pore-filling ratio (PFR), a ratio of pore filling in the components by the liquid carbonate electrolytes, was used to determine the optimum performance range. Consequently, 77% PFR demonstrated the optimum performance for both electrolytes. Thus, the MCFC had a permissible but narrow optimum performance range. The remaining amounts of electrolyte in the cells were determined using the weight reduction ratio (WRR) method after several hours of cell operation. The WRR used the relationship between the initial loaded amount of electrolyte and weight reduction of components in 10 wt% acetic acid. The relationships were linear and identical between the two electrolyte species.

Characteristics of Solid Fuel Oxidation in a Molten Carbonate Fuel Cell

  • Lee, Choong-Gon;Kim, Yu-Jeong;Kim, Tae-Kyun;Lee, Sang-Woo
    • Journal of Electrochemical Science and Technology
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    • v.7 no.2
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    • pp.91-96
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    • 2016
  • Oxidation behaviours of ash free coal (AFC), carbon, and H2 fuels were investigated with a coin type molten carbonate fuel cell. Because AFC has no electrical conductivity, its oxidation occurs via gasification to H2 and CO. An interesting behaviour of mass transfer resistance reduction at higher current density was observed. Since the anode reaction has the positive reaction order of H2, CO2 and H2O, the lack of CO2 and H2O from AFC results in a significant mass transfer resistance. However, the anode products of CO2 and H2O at higher current densities raise their partial pressure and mitigate the resistance. The addition of CO2 to AFC reduced the resistance sufficiently, thus the resistance reduction at higher current densities did not appear. Electrochemical impedance results also indicate that the addition of CO2 reduces mass transfer resistance. Carbon and H2 fuels without CO2 and H2O also show similar behaviour to AFC: mass transfer resistance is diminished by raising current density and adding CO2.

Study on the Thickness Effect of the Separator for Lithium Secondary Batteries (리튬이차전지용 분리막의 두께에 따른 특성 연구)

  • Kim, Sang Woo;Seok, Ji-Hoo;Kim, Byung-Hyun Daniel;Cho, Hee-Min;Cho, Kuk Young
    • Journal of the Korean Electrochemical Society
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    • v.17 no.1
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    • pp.7-12
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    • 2014
  • There is increasing demand on the reducing the weight and the volume of the major components in lithium secondary battery to improve energy density. Separator not only provides pathway for lithium ion movement but also prevents direct contact between anode and cathode. Herein we fabricated polyethylene separator by varying biaxial stretching ratio to obtain membrane thickness of 16, 12, and $9{\mu}m$. Mechanical and thermal properties of the separator with different thickness were investigated. Also rate capability and charge-discharge cycle property up to 500 cycles were studied using coin type full-cell with $LiCoO_2$ and graphite as a cathode and an anode, respectively. All the cells using separator with different thickness demonstrated excellent capacity retention after 500cycles (around 80%). Considering the rate capability, cell using separator with thickness of $9{\mu}m$ showed best performance. Interestingly, separator thickness of $9{\mu}m$ was more resistant to heat contraction compared to that of $16{\mu}m$ separator.

Novel Design of Two-Phase PM Vibration Motor Used for Cell-Phones (새로운 형태의 휴대폰용 2 상 진동모터의 설계)

  • Lee, Hong-Joo;Kim, Kwang-Suk;Lee, Chang-Min;Hwang, Gun-Yong;Hwang, Sang-Moon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.218-223
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    • 2008
  • Cell-phone becomes a necessary communication device in modern society. However, a paging signal by a sound transducer often acts as an unpleasant noise, thus necessitating a paging signal by a vibration motor. The conventional flat type vibration motor uses three-phase windings with three phase coils. In this article, a new design of a vibration motor using a V connection with two phase coils is presented, increasing mass productivity. For electromagnetic field analysis, due to the motor symmetry, two-dimensional modeling can be implemented for fast computation, and performance is predicted by the finite element method. The winding distribution angle turns out to be the most important design parameter for the elimination of dead points, and a new coil configuration is suggested which has no adverse effect on motor size and weight. Experimental tests of vibration confirm the validity of the proposed design.

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Electrochemical Characteristics of Graphite/Silicon/Pitch Anode Composites for Lithium Ion Batteries using Silica-Coated Graphite (실리카로 코팅된 흑연을 이용한 리튬 이차전지용 흑연/실리콘/피치 복합소재의 전기화학적 특성)

  • Lee, Su Hyeon;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.58 no.1
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    • pp.142-149
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    • 2020
  • In this study, the electrochemical performance of Graphite/Silicon/Pitch composites as anode material was investigated to improve the low theoretical capacity of artificial graphite. Spherical artificial graphite surface was coated with polyvinylpyrrolidone (PVP) amphiphiles material to synthesize Graphite/Silica material by silica islands growth. The Graphite/Silicon/Pitch composites were prepared by petroleum pitch coating and magnesiothermic reduction. The Graphite/Silicon/Pitch composite electrodes manufactured using poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) binders. The coin type half cell was assembled using various electrolytes and additives. The Graphite/Silicon/Pitch composites were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and a thermogravimetric analyzer (TGA). The electrochemical characteristics of Graphite/Silicon/Pitch composite were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy. The Graphite/Silicon/Pitch composites showed high cycle stability at a graphite/silica/pitch ratio (1:4:8 wt%). When the electrode is prepared using PAA binder, the high capacity and stability is obtained. The coin type half cell assembled using EC: DMC: EMC electrolyte showed high initial capacity (719 mAh/g) and excellent cycle stability. The rate performance has an capacity retention (77%) at 2 C/0.1 C and an capacity recovery (88%) at 0.1 C / 0.1 C when the vinylene carbonate (VC) was added.