• Title, Summary, Keyword: Lithium Secondary Battery

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Electrochemical Characteristics of LiNi0.5Mn1.5O4 Spinel as 5 V Class Cathode Material for Lithium Secondary Batteries (5V급 고전압 양극 LiNi0.5Mn1.5O4 Spinel의 제조와 전기화학적 특성에 관한 연구)

  • Jeon, Sang-Hoon;Oh, Si-Hyoung;Lee, Byung-Jo;Cho, Won-Il;Cho, Byung-Won
    • Journal of the Korean Electrochemical Society
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    • v.8 no.4
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    • pp.172-176
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    • 2005
  • Recently, many researches on the high-voltage 5 V class cathode material have focused on $LiNi_{0.5}Mn_{1.5}O_4$, where $Mn^{3+}$ in the existing $LiMn_2O_4 (Li[Mn^{3+}][Mn^{4+}]O_4)$ is replaced by $Ni^{2+}(Li[Ni^{2+}]_{0.5}[Mn^{4+}]_{1.5}O_4)$ in order to utilize $Ni^{2+}/Ni^{4+}$ redox reaction in the 5V region. The partial substitution of Mn in $LiMn_2O_4$ for other transition metal element, $LiM_yMn_{1-y}O_4$(M=Cr, Al, Ni, Fe, Co, Cu, Ga etc) is known as a good solution to overcome the problems associated with $LiMn_2O_4$ like the gradual capacity fading. In this study, we synthesized $LiNi_{0.5}Mn_{1.5}O_4$ through a mechanochemical process and investigated its morphological, crystallographic and electrochemical characteristics. The results showed that 4 V peaks had been found in the cyclic volammograms of the synthesized powders due to the existence of $Mn^{3+}$ from the incomplete substitution of $Ni^{2+}$ for $Mn^{3+}$ implying that the mechanochemical activation alone was not good enough to synthesize an exact stoichiometric compound of $LiNi_{0.5}Mn_{1.5}O_4$. The synthetic condition of mechanochemical process, such as type of starting materials, ball-mill and calcination condition was optimized for the best electrochemical performance.

The Structural and Electrochemical Properties of Li[Ni0.6-xBaxCo0.1Mn0.3]O2 (x = 0, 0.01) by Barium Doping (Barium 도핑에 따른 Li[Ni0.6-xBaxCo0.1Mn0.3]O2(x=0, 0.01) 의 구조 분석 및 전기화학적 특성)

  • Jang, Byeong-Chan;Yoo, Gi-Won;Yang, Su-Bin;Min, Song-Gi;Son, Jong-Tae
    • Journal of the Korean Electrochemical Society
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    • v.17 no.4
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    • pp.222-228
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    • 2014
  • Ni-rich system $Li[Ni_{1-x-y}Co_xMn_y]O_2$ of lithium secondary battery cathode material keep a high discharge capacity. However, by the Ni content increases, there is a problem that the electrochemical properties and stability of the structure are reduced. In order to solve these problems, research for positive ion doping is performed. The one of the cathode material, barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01), was synthesized by the precursor, $Ni_{0.6}Co_{0.1}Mn_{0.3}(OH)_2$, from the co-precipitation method. The barium doped materials have studied the structural and electrochemical properties. The analysis of structural properties, results of X-ray diffraction analysis, and those results confirmed the change of the lattice from the binding energy in the structure by barium doping. Increased stability of the layered structure was observed by $I_{(006)}+I_{(102)}/I_{(101)}$(R-factor) ratio decrease. we expected that the electrochemical characteristics are improved. 23 mAh/g discharge capacity of barium-doped $Li[Ni_{0.6-x}Ba_xCo_{0.1}Mn_{0.3}]O_2$ (x=0.01) electrode is higher than discharge capacity of $Li[Ni_{0.6}Co_{0.1}Mn_{0.3}]O_2$ due to decrease overvoltage. And, through the structural stability was confirmed that improved the cycle characteristics. We caused a reduction in charge transfer resistance between the electrolyte and the electrode was confirmed that the C-rate characteristics are improved.

A Study on the chemical analysis of synthesized Li-AGICs with changes of intercalant contents (Intercalant 함량 변화에 따라 합성된 Li-AGICs의 화학적 분석에 관한 연구)

  • Oh, Won-Chun;Shim, Sang-Kyun
    • Analytical Science and Technology
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    • v.10 no.3
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    • pp.209-215
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    • 1997
  • Li-AGICs as a anode of secondary battery were synthesized by high-pressure method as a function of the Li-contents. The characteristics of these prepared compounds were determined from the studies with X-ray diffraction method, UV/VIS spectrophotometric and differential scanning calorimeter(DSC) analysis. From the results of X-ray diffraction, it was found that the lower stage intercalation compounds were formed with increase of Li-contents. The mixed stages in these compounds were also observed. In the case of the $Li_{30wt%}$-AGIC, the compounds in the stage 1 structure were formed predominantly, but the structure of only pure stage 1 for structural defect of artificial graphite is not observed. According to UV/VIS spectrophotometric analysis, $Li_{30wt%}$-AGIC shows distinguishable energy state spectrum with the position of $R(%)_{min}$ values, but the characteristic spectra of almost all Li-AGICs are not observed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From the results, it was found that exothermic and endothermic reactions of Li-AGICs are related to thermal stability of lithium between artificial graphite layers.

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The study on the variaty of anode materials, $C_6Li$ for secondary battery (2차 전지 음극 재료용 $C_6Li$의 다양화에 관한 연구)

  • 오원춘;김범수;이영훈;고영신
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.4
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    • pp.660-666
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    • 1998
  • We discussed structure, energy state, characteristics of thermal stability, and electrochemical properties of Li-GFICs, Li-PCICs, and Li-AGICs during the intercalation process. According to X-ray diffraction patterns, we observed phase of stage 2 mainly from Li-GFICs, while stage 1 phase as well as stage 2 from Li-PCICs. For the structure of Li-AGICs, stage 1 phase was dominant, but it was not possible to obtain pure stage 1 compound probably due to structural characteristics of artificial graphite. We measured energy state of the compounds to stage stability, and revealed that Li-AGICs and Li-GFICs were in more stable state than Li-PCICs. Therefore, those two compounds could be excellent candidate for energy reserve material. From the study of thermal degradation, Li-GFICs showed strong exothermic reaction at around 300 and $400^{\circ}C$. In the study of thermal stability of Li-AGIC at various temperatures, we observed that lithium was not completely deintercalated and high stage was maintained even at high temperature. In the case of charge, discharge, and electrochemical studies, Li-GFICs showed the best results.

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Stabilization of LiMn2O4 Electrode for Lithium Secondary Battery(I) - Electrode Characteristics on the Substitution of Metal Oxides in LiMn2O4 Cathode Material - (리튬이차전지용 정극활물질 LiMn2O4의 안정화(I) - LiMn2O4에 대한 금속산화물의 치환에 따른 전극 특성 -)

  • Lee, Jin-Sik;Lee, Chul-Tae
    • Applied Chemistry for Engineering
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    • v.9 no.5
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    • pp.774-780
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    • 1998
  • For the stabilization of the spinel structured $LiMn_2O_4$, a fraction of manganese was substituted with various metals such as Mg, Fe, V, W, Cr, Mo with Mn that had a similar ionic radii ($LiM_xMn_{2-x}O_4(0.05{\leq}x{\leq}0.02)$). The $LiM_xMn_{2-x}O_4$ showed a substantial improvement as lower capacity loss than that of the spinel structured $LiMn_2O_4$ when it was used as a cathode material. And with the partial substitution, the chemical diffusion coefficient for $LiMg_{0.05}Mn_{1.9}O_4$ and $LiCr_{0.1}Mn_{1.9}O_4$ was increased by and order of magnitude compared to that of the $LiMn_2O_4$ with spinel structure. The results showed that significant improvement can be made on the electrochemical characteristics as the structure of the $LiMn_2O_4$ electrode material was stabilized by the partial substitution.

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An Electrochemical Study on the Carbon Black Conductor Prepared by Plasma Pyrolysis of Methane (메탄 플라즈마 분해에 의해 제조된 카본블랙 도전재의 전기화학적 특성에 대한 연구)

  • Yoon, Se-Rah;Lee, Joong-Kee;Cho, Won-Ihl;Baek, Young-Soon;Ju, Jae-Beck;Cho, Byung-Won
    • Journal of the Korean Electrochemical Society
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    • v.6 no.1
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    • pp.6-12
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    • 2003
  • Plasma carbon black(PB) which prepared by plasma pyrolysis of methane was treated at 800, 1300 and $2100^{\circ}C$ under $2\times10^{-2}$ torr. Four different samples including raw PB were added to $LiCoO_2$, cathode active material of lithium secondary battery, to investigate effects of properties of plasma black as conductors on electrochemical characteristics. Based on our experimental results, PB conductors with low amount of surface functional groups and high electrical conductivity enhanced the cyclability and the initial discharge capacity. However, deterioration of rate capability and cyclability were observed (or the plasma black treated at $2100^{\circ}C$ For the plasma black conductor prepared from plasma pyrolysis, the effects of properties of carbon black on electrochemical characteristics were combined results of changes in electrical conductivity and structural properties such as agglomeration of plasma black. The conductivity of plasma black increased with treatment temperature, while dispersion of plasma black decreased. As a result, the high cyclability of cell was observed at $800^{\circ}C$ of heat treatment temperature.

Synthesis and Electrochemical Properties of LiFePO4 Cathode Material obtained by Electrospinning Method (전기방사법을 이용한 LiFePO4 양극 활물질의 합성 및 전기화학적 특성)

  • Lee, Seung-Byung;Cho, Seung-Hyun;Park, Sun-Il;Lee, Wan-Jin;Lee, Yun-Sung
    • Journal of the Korean Electrochemical Society
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    • v.11 no.4
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    • pp.268-272
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    • 2008
  • $LiFePO_4$ material was synthesized by electrospinning method to obtain optimal particle size($50{\sim}100\;nm$) without carbon coating or ball milling. This material showed an orthorthombic structure with Pnma space group without any impurities, such as FeP or $Fe_2P$, in the XRD pattern. The particle morphology and particle shape were observed by SEM analysis. Li/$LiFePO_4$ cell showed a high initial discharge capacity of 135 mAh/g, at current density of $0.1\;mA/cm^2$ with a cut-off voltage of 2.8 to 4.0V. This cell exhibited a perfect cycle performance over 99.9% cycle retention rate up to 50 cycles.

Synthesis and Electrochemical Characterization of Polyaniline/Poly[1,2]bis-thio[1,8]-naphthylidine Composite as Polymer Cathode Material (Polyaniline/Poly[1,2]bis-thio[1,8]-naphthylidine 복합체 고분자 양극재료의 합성과 전기화학적 특성)

  • Oh, Ji-Woo;Ryu, Kwang-Sun
    • Journal of the Korean Electrochemical Society
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    • v.15 no.4
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    • pp.222-229
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    • 2012
  • We studied the electrochemical phenomena and increase of capacity according to the polymer composite electrode of two different polymeric materials with different the voltage range and capacity. Polyaniline (PANI) with relatively high voltage and small capacity and poly [1,2] bis-thio[1,8]-naphthylidine (PTND) with slightly low voltage and large capacity were used as polymer composite electrode materials. After PTND was synthesized, PANI was synthesized on the surface of PTND. The synthesis and the fine structure were analyzed by FT-IR, XPS, FE-SEM, and FE-TEM. Charge/discharge capacity and cyclic voltammetry measurements were carried out for the electrochemical performance as a polymer cathode active material for lithium secondary batteries. The discharge capacities of PANI/PTND after 1,5, and 10 cycles at 1.3~4.0 V voltage range and room temperature 167 mAh/g, 90 mAh/g, and 81 mAh/g. When we compared with PANI (80, 67, and 62 mAh/g), the discharge capacity after 10 cycles was improved about 30%. After 50 cycles, the discharge capacity of PANI/PTND was 67 mAh/g.

Influence of Precursor on the Electrochemical Properties of Li(Ni0.5Co0.2Mn0.3)O2 Cathode for the Lithium Secondary Battery (전구체의 물성에 따른 리튬 2차전지용 Li(Ni0.5Co0.2Mn0.3)O2의 전기화학적 특성 변화)

  • Kang, Donghyun;Arailym, Nurpeissova;Chae, Jeong Eun;Kim, Sung-Soo
    • Journal of the Korean Electrochemical Society
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    • v.16 no.4
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    • pp.191-197
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    • 2013
  • The one of the cathode material, $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$, was synthesized by the precursor, $Ni_{0.5}Co_{0.2}Mn_{0.3}(OH)_2$, from the co-precipitation method and the morphologies of the primary particle of precursors were flake and needle-shape by controlling the precipitation parameters. Identical powder properties, such as particle size, tap density, chemical composition, were obtained by same process of lithiation and heat-treatment. The relation between electrochemical performances of $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$ and the primary particle morphology of precursors was analyzed by SEM, XRD and EELS. In the $Li(Ni_{0.5}Co_{0.2}Mn_{0.3})O_2$ cathode from the needle-shape precursor, the primary particle size was smaller than that from flake-shape precursor and high Li concentration at grain edge comparing grain center. The cycle and rate performances of the cathode from needle-shape precursor shows superior to those from flake-shape precursor, which might be attributed to low charge-transfer resistance by impedance measurement.

Syntheses of LiMn1.92Co0.08O4 and LiNi1-yCoyO2 and Electrochemical Properties of their Mixtures for Lithium Secondary Battery (리튬 이차전지용 LiMn1.92Co0.08O4, LiNi1-yCoyO2 의 합성과 그들의 혼합물의 전기화학적 특성)

  • Kwon, IkHyun;Kim, HunUk;Song, MyoungYoup
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.1
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    • pp.62-71
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    • 2004
  • $LiMn_{1.92}Co_{0.08}O_4-x\;wt.%LiNi_{0.7}Co_{0.3}O_2$를 단순화한 연소법에 의하여 합성하고, 그것들의 전기화학적 특성을 조사하였다. 또한 30분동안 밀링하여 준비한 $LiMn_{1.92}Co_{0.08}O_4-x\;wt.%LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41 and 47) 혼합물 전극의 전기화학적 특성을 조사하였다. x=33 조성의 전극이 가장 큰 초기방전용량(132.0mAh/g at 0.1C)을 나타내었다. x=9조성의 전극은 비교적 큰 초기방전용량(109.9mAh/g at 0.1C)과 우수한 싸이클 특성을 나타내었다. 싸이클링에 따른 혼합물 전극의 방전용량의 감소는 주로 $LiNi_{0.7}Co_{0.3}O_2$의 퇴화에 기인한다고 생각된다. 그런데 $LiNi_{0.7}Co_{0.3}O_2$의 퇴화는 $LiMn_{1.92}Co_{0.08}O_4$로부터 용해된 Mn이 $LiNi_{0.7}Co_{0.3}O_2$를 둘러쌈(coating)으로써 야기되는 것으로 생각된다.