• Title, Summary, Keyword: Charge and discharge capacities

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A Study on the Electrochemical Hydrogenation Reaction Mechanism of the Laves Phase Hydrogen Storage Alloys (Laves phase계 수소저장합금의 전기화학적 수소화 반응 매카니즘에 관한 연구)

  • Lee, Ji-Youl;Kim, Chan-Jung;Kim, Dai-Ryong
    • Transactions of the Korean hydrogen and new energy society
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    • v.8 no.1
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    • pp.31-41
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    • 1997
  • In order to investigate the mechanism of electrochemical hydrogenation reaction on Zr-based Laves phase hydrogen storage alloy electrodes, electrochemical charge/discharge characteristics, potentiostatic/dynamic polarizations and electrocehmical impedance spectroscopy(EIS) of Zr-Ti-Mn-Ni and Zr-Ti-Mn-Ni-M(M=Fe, Co, Al) alloys were examined. Electrochemical discharge capacities of the alloys were quite different with gas charge capacities. Therefore, it was considered that discharge capacities of the alloys depend on electrochemical kinetic factors rather then thermodynamic ones. Discharge efficiencies were increased linearly with exchange current densities. The results of potentiostatic/dynamic polarization measurements showed that electrochemical charge and discharge reaction of Zr-based Laves phase hydrogen storage alloys is controlled by charge transfer process at the electrode surface. The EIS measurements also confirmed this result.

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Electrochemical Charge and Discharge Characteristics of Zr-Based Laves Phase Hydrogen Storage Alloys (Zr계 라-베상 수소저장합금의 전기화학적 충·방전특성)

  • Lee, Jae-Myoung;Kim, Chan-Jung;Kim, Dai-Ryong
    • Transactions of the Korean hydrogen and new energy society
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    • v.5 no.2
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    • pp.99-109
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    • 1994
  • To develop high capacity hydrogen storage alloys for secondary Ni/MH batteries, electrochemical charge/discharge characteristics of $Zr_{1-x}Ti_xMn_{1-y}V_yNi_{1-z}M_z$ (M=Al,Co,Fe) alloys were investigated, in which $0.2{\leq}x{\leq}0.6$, $0.2{\leq}y{\leq}0.8$, $0.2{\leq}z{\leq}0.4$. With increasing Ti content(x) and/or decreasing V content(y), lattice constants and maximum theoretical capacities of the alloys were decreased and equilibrium pressure of hydrogen absorption were increased. Electrochemical discharge capacities were increased with increasing Ti content(x). Especially, the alloys of x= 0.4~0.6 showed better charge/discharge efficiencies than those of x<0.4. Discharge capacities of $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Fe_{0.2}$, $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Al_{0.2}$ and $Zr_{0.5}Ti_{0.5}Mn_{0.4}V_{0.6}Ni_{0.6}Co_{0.4}$ were 385, 328 and 333mAh/g, respectively. These alloys were fully activated within five charge/discharge cycles and had a good charge and discharge rate capabilities and temperature characteristics.

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Charge-discharge Properties of Positive Active Material Li(Cr0.4Mn0.6)O2 (정극 활물질 Li(Cr0.4Mn0.6)O2의 충ㆍ방전 특성)

  • Wee, Sung-Dong;Jeong, In-Seong;Gu, Hal-Bon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.10
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    • pp.1085-1089
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    • 2004
  • An impedance properties of the positive active material Li(Cr$_{0.4}$Mn$_{0.6}$)O$_2$ are measured by the changeable trend to the time. The charge-discharge capacities of 297 mAh(g)$^{-1}$ 175 mAh(g)$^{-1}$ are obtained by the made cell with the active material that the Cr was added to LiMnO$_2$ to prevent structural degradation of an electrode active material with impedance of 75 Ω to get at an initial hour. Resultantly, these variations which the impedances enhanced continually, were not watched the impeditive variations as the results of the delay time that the positive thin films and the references have been soaked all together in the solution of electrolyte of 1M LiPF$_{6}$ EC/DEC(l/2). Accordingly, it means an amount increased of the discharged capacities in the view of the results that the impeditive values were decreased are known already through a authorized paper.per.

Electrochemical Property of Positive Active Material $LiMnO_2$ (정극 활물질 $LiMnO_2$의 전기 화학적 특성)

  • Wee, Sung-Dong;Kim, Jong-Uk;Kim, Min-Sung;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.803-806
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    • 2003
  • The impedance of the positive active material $LiMnO_2$ is measured by the changeable trend following the time. The charge capacities of single cell and each cells of four made with thin film prepared in the dry box are measured after measuring the impedance with the interval of 0, 24, 48 and 72 hours. In result, the impedance through the delaying time is not enhanced continuously as result of the time. The variation of capacity enhanced is not watched as the result of the delaying time that all together of the positive thin film and the reference is soaked in the solution of electrolyte of 1M PC $LiClO_4$. But it can be known to increase the discharge capacities as that the impeditive value is decrease.

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The Synthesis and Charge/discharge Properties of $LiNiO_2$ according to heat treatment condition (열처리 조건에 따른 $LiNiO_2$의 합성과 충방전 특성)

  • Lee, H.N.;Chun, D.G.;Choi, H.K.;Kim, K.S.;Gu, H.B.
    • Proceedings of the KIEE Conference
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    • pp.1603-1605
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    • 1997
  • $LiNiO_2$ is prepared by heating LiOH $H_2O$ and $Ni(OH)_2$ (mole ratio 1:1). In this study, we investigated X-ray diffraction, and charge/discharge property heat treatment condition and conductive agent sort and volume of $LiNiO_2$ prepared at various temperature and time. All $LiNiO_2$ prepared at this study showed hexagonal structure. In charge/discharge capacities, heated at $O_2$ than air and $750^{\circ}C$ than $700^{\circ}C$, specific capacity is higher. Therefore, when preliminary heat at $650^{\circ}C$ $O_2$ and heat at $750^{\circ}C$ carried out, charge/discharge property is best.

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Development of Silicone coated by Carbon driven PVDF and its anode characteristics for Lithium Battery (전구체로서 PVDF를 이용한 탄소 도포 실리콘 재료의 개발 및 리튬이차전지 음극 특성)

  • Doh, Chil-Hoon;Jeong, Ki-Young;Jin, Bong-Soo;Kim, Hyun-Soo;Moon, Seong-In;Yun, Mun-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.350-351
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    • 2005
  • The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

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A Study on the Impedance Characteristics and Mechanisms of Li Intecalation on the Tin Oxide-flyash Composite Electrodes (Tin Oxide-flyash Composite 전극의 리튬 이온 Intercalation 메카니즘과 임피던스 특성에 관한 연구)

  • Gu, Hal-Bon;Kim, Jong-Uk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.11
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    • pp.1224-1229
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    • 2004
  • The purpose of this study is to research and develop tin oxide-flyash composite for lithium Ion polymer battery. Tin oxide is one of the promising material as a electrode active material for lithium Ion polymer battery (LIPB). Tin-based oxides have theoretical volumetric and gravimetric capacities that are four and two times that of carbon, respectively. We investigated cyclic voltammetry, AC impedance and charge/discharge cycling of SnO$_2$-flyash/SPE/Li cells. The first discharge capacity of SnO$_2$-flyash composite anode was 639 mAh/g. The discharge capacity of SnO$_2$-flyash composite anode was 563 and 472 mAh/g at 6th and 15th cycle, respectively. The SnO$_2$-flyash composite anode with PVDF-PMMA-PC-EC-LiClO$_4$ electrolyte showed good capacity with cycling.

Development of Silicon Coated by Carbon with PVDF Precursor and Its Anode Characteristics for Lithium Batteries (PVDF 전구체를 이용한 탄소 도포 실리콘 재료의 개발 및 리튬이차전지 음극특성)

  • Doh, Chil-Hoon;Jeong, Ki-Young;Jin, Bong-Soo;Kim, Hyun-Soo;Moon, Seong-In;Yun, Mun-Soo;Choi, Im-Goo;Park, Cheol-Wan;Lee, Kyeong-Jik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.7
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    • pp.636-643
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    • 2006
  • Si-C materials were synthesized by the heating the mixture of silicon and polyvinylidene fluoride (PVDF). The electrochemical properties of the Si-C materials as the high capacitive anode materials of lithium secondary batteries were evaluated by the galvanostatic charge-discharge test through 2032 type $Si-C{\mid}Li$ coin cells. Charge-discharge tests were performed at C/10 hour rate(C = 372 mAh/g). Initial discharge and charge capacities of $Si-C{\mid}Li$ cell using a Si-C material derived from PVDF(20wt.%) were found to be 1,830 and 526 mAh/g respectively. The initial discharge-charge characteristics of the developed Si-C electrode were analyzed by the electrochemical galvanostatic test adopting the capacity limited charge cut-off condition(GISOC). The range of reversible specific capacity IIE(intercalation efficiency at initial discharge-charge) and IICs(surface irreversible specific capacity) were 216 mAh/g, 68 % and 31 mAh/g, respectively.

Electrochemical Properties of Hydrogen Absorbing Ability Ti1-XZrxVNi Ti1-XZrxV0.5Ni1.5 Alloys (Ti1-XZrxVNi 및 Ti1-XZrxV0.5Ni1.5계 수소저장합금의 전기화학적 성질)

  • Cho, Tae-Hwan;Park, Chan-Kyo
    • Transactions of the Korean hydrogen and new energy society
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    • v.2 no.1
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    • pp.15-21
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    • 1990
  • Nickel-hydrogen battery systems with metal hydride alloys are expected to have both higher energy density and lower pollution than nickel-cadmium cells. Nickel-hydrogen storage cells are expected to be well-suited for use in space crafts for a large capacity power storage system. Their major advantages are not only a capability of deep DOD(depth of discharge) using but also with excellent durability under excessive overcharging and overdischarging. In this study, the charge/discharge capacities, anodic polarization characteristics and durability for the continious charge/diacharge cycling of the $Ti_{1-X}Zr_XVNi$ and $Ti_{1-X}Zr_XV_{0.5}Ni_{1.5}$ alloys were measured by electrochemical method. The electrode properties of the copper or nickel plated $Ti_{1-X}Zr_XV_{0.5}Ni_{1.5}$ alloys were examined with a battery charge/discharge testing system in the temperature range of -5 to $25^{\circ}C$.

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Physicochemical and Electrochemical Characteristics of Carbon Nanomaterials and Carbon Nanomaterial-Silicon Composites

  • Kim, Soo-Jin;Hyun, Yura;Lee, Chang-Seop
    • Journal of the Korean Chemical Society
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    • v.60 no.5
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    • pp.299-309
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    • 2016
  • In this study, the physicochemical and electrochemical properties of carbon nanomaterials and synthesized nano-carbon/Si composites were studied. The nano-carbon/Si composites were ball-milled to a nano size and coated with pyrolytic carbon using Chemical Vapor Deposition (CVD). They were then finely mixed with respective nano-carbon materials. The physicochemical properties of samples were analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Raman spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and surface area analyzer. The electrochemical characteristics were investigated using the galvanostatic charge-discharge and cyclic voltammetry (CV) measurements. Three-electrode cells were fabricated using the carbon nanomaterials and nano-carbon/Si composites as anode materials and LiPF6 and LiClO4 as electrolytes of Li secondary batteries. Reversibility using LiClO4 as an electrolyte was superior to that of LiPF6 as the electrolyte. The initial discharge capacities of nano-carbon/Si composites were increased compared to the initial discharge capacities of nano-carbon materials.