• Title/Summary/Keyword: LI4

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7Li MAS NMR studies of Li4P2O7 and LiFePO4 materials (LiFePO4와 Li4P2O77Li MAS NMR 특성 연구)

  • Han, Doug-Young;Park, Nam-Sin;Lee, Sang-Hyuk;Lee, Hak-Man;Kim, Chang-Sam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.21 no.1
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    • pp.15-20
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    • 2011
  • [ $^7Li$ ]Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in $Li_4P_2O_7$ and$LiFePO_4$ materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of $LiFePO_4$ as cathode material. $Li_4P_2O_7$ and $LiFePO_4$ were prepared by a solid-state reaction. The $^7Li$ MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in $Li_4P_2O_7$ system. The $^7Li$ MAS NMR spectra of in $Li_4P_2O_7$ indicate that the lithium local environments in $Li_4P_2O_7$ were not changed in the temperature range between $27^{\circ}C$ and $97^{\circ}C$ Through this work, we confirmed that the small amount of $Li_4P_2O_7$ less than 5.0 wt% in $LiFePO_4$ could be clearly measured by the $^7Li$ MAS NMR spectroscopy at high spinning rate over than 11 kHz.

Charge/Discharge Properties of Camon Added $LiFeO_4$

  • Jin, En-Mei;Li, Hu;Jeon, Yeon-Su;Park, Kyung-Hee;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.361-362
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    • 2007
  • Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD) and FE-SEM. $LiFePO_4/SPE/Li$ and $LiFePO_4$-C/SPE/Li cells were characterized electrochemically by charge/discharge experiments. The results showed that the discharge capacity of $LiFePO_4$-C/SPE/Li cell was 103 mAh/g at the first cycle. The discharge capacity of $LiFePO_4$-C/SPE/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/SPE/Li cells, 126 mAh/g at the first cycle and 123 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/SPE/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/SPE/Li cell.

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The relation of the crystal phase and the charge/discharge capacity of $Li[Li_yMn_{2-y}]O_4$ cathode materials substituted Li (Li 치환된 $Li[Li_yMn_{2-y}]O_4$ 정극 활물질의 결정 구조와 충방전 용량과의 관계)

  • Jeong, In-Seong;Gu, Hal-Bon;Park, Bok-Gi;Son, Myeng-Mo;Lee, Heon-Su
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.04b
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    • pp.117-120
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    • 2000
  • The relation of crystal phase and charge/discharge capacity of $Li[Li_yMn_{2-y}]O_4$ were studied for different degrees of Li substitution (y). All cathode material showed spinel phase based on cubic phase in X-ray diffraction. Other peaks didn't show in spite of the increase of y value in $Li[Li_yMn_{2-y}]O_4$. Ununiform of $Li[Li_yMn_{2-y}]O_4$ which calcinated by (111) face and (222) face was more stable than that of pure $LiMn_2O_4$. In addition, At TG analysis, calcined $Li[Li_{0.1}Mn_{1.9}]O_4$ exhibited much mass loss at $800{\mu}m$. The cycle performance of the $Li(Li_yMn_{2-y}]O_4$ was improved by the substitution of $Li^{1+}$ for $Mn^{3+}$ in the octahedral sites. Specially, $Li[Li_{0.08}Mn_{1.92}]O_4$ and $Li[Li_{0.1}Mn_{1.9}]O_4$ cathode materials showed the charge and discharge capacity of about 125mAh/g at first cycle, and about 95mAh/g after 70th cycle. It is excellent than that of pure $LiMn_2O_4$, which 125mAh/g at first cycle, 65mAh/g at 70th.

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Synthesis LiFePO4- poly(sodium 4-styrenesulfonate) composite cathode material for rechargeable lithium battery by hydrothermal method

  • Hiep, Nguyen Van;Wang, Wan Lin;Jin, En Mei;Gu, Hal-Bon
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.137.2-137.2
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    • 2011
  • Poly (sodium 4-styrenesulfonate) (PSS) is ionomer based on polystyrene that is electrical conductivity and isoviscosity. LiFePO4 has been a promising electrode material however its poor conductivity limits practical application. To enhance the electronic conductivity of LiFePO4, in this study we prepared LiFePO4- PSS composite by the hydrothermal method. LiFePO4 was heated at $170^{\circ}C$ for 12h and then different wt% PSS (0%, 2.91%, 4.75%, 7.36%, 10%) are added to LiFePO4 and milled at 300rpm for 10h. And then the obtained powders were subsequently heated at $500^{\circ}C$ for 1h under argon flow. The cathode electrode were made from mixtures of LiFePO4-PSS: SP-270- PVDF in a weighting ratio 75%: 25%:5%. The electrochemical properties of LiFePO4- PSS/Li batteries were analyzed by cyclic voltammetry and charge/discharge tests. LiFePO4-C/Li battery with 4.75 wt% PSS displays discharge capacity of 128 mAh g-1 at room temperature that is considerably higher than pure LiFePO4/Li battery ( 113.48 mAhg-1).

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Fabrication and Characterization of ${LiMn_2}{O_4}$ Cathode for Lithium Rechargeable Battery by R.F.Magnetron Sputtering (R.F. Magnetron Sputtering을 이용한 리튬이차전지 정극용 ${LiMn_2}{O_4}$의 제조 및 특성)

  • 우태욱;손영국
    • Journal of the Korean Ceramic Society
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    • v.37 no.6
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    • pp.552-558
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    • 2000
  • LiMn2O4 thin fiolm cathodes for Li-ion secondary battery were fabricated by r.f. magnetron sputtering technique. As-deposited films were amorphous. A spinel structure could not be obtained LiMn2O4 films by in-situ thermal annealing. After post thermal annealing over $700^{\circ}C$ in oxygen atmosphere, LiMn2O4 films prepared above 100 W r.f. power could be crystallized into a spinel structure. The electrochemical property of the LiMn2O4 film cathodes was tested in a Li/1 M LiClO4 in PC/LiMn2O4 cell. From cyclic voltammetry at scan rate of 2mV/sec of 2.5~4.5V, LiMn2O4 electrode prepared by post annealing at 75$0^{\circ}C$ showed good initial capacity. LiMn2O4 electrode prepared by post annealing at 80$0^{\circ}C$ showed the best crycling performance.

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Structural and Electrochemical Characterization of LiFePO4 Synthesized by Hydrothermal Method

  • Jeon, Yeon-Su;Jin, En-Mei;Jin, Bo;Jun, Dae-Kyoo;Han, Zhen-Ji;Gu, Hal-Bon
    • Transactions on Electrical and Electronic Materials
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    • v.8 no.1
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    • pp.41-45
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    • 2007
  • Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4$-C/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4$-C/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/Li cell.

Structural and Electrochemical Characterization of $LiFePO_4$ Synthesized by Hydrothermal Method

  • Jeon, Yeon-Su;Jin, En-Mei;Jin, Bo;Jun, Dae-Kyoo;Han, Zhen Ji;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.12a
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    • pp.48-52
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    • 2006
  • Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity' of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). $LiFePO_4$/Li and $LiFePO_4-C$/Li cells were characterized electrochemically by cyclic voltammogram (CV), charge/discharge experiments and ac impedance spectroscopy. The results showed that the discharge capacity of $LiFePO_4$/Li cell was 147 mAh/g at the first cycle and 118 mAh/g after 30 cycles, respectively. The discharge capacity of $LiFePO_4-C$/Li cell with 5wt% carbon black was the largest among $LiFePO_4-C$/Li cells, 133 mAh/g at the first cycle and 128 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4-C$/Li cell with 5wt% carbon black was better than that of $LiFePO_4$/Li cell.

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Electrochemical Characteristics of $LiFePO_4$ with Conductivity Materials for Lithium Polymer Batteries

  • Jin, En Mei;Wang, Jiao;Zhao, Xing Guan;Park, Kyung-Hee;Gu, Hal-Bon;Park, Bok-Kee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.132-132
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    • 2009
  • Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. In this study, Multi-walled carbon nanotube (MWCNT) and Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. $LiFePO_4$, $LiFePO_4$-MWCNT and $LiFePO_4$-C particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) transmission electron microscope (TEM). $LiFePO_4/SPE/Li$, $LiFePO_4$-MWCMT/SPE/Li and $LiFePO_4$-C/SPE/Li cells were characterized electrochemically by charge/discharge experiments at a constant current density of $0.1mA\;cm^{-2}$ in a range between 2.5 and 4.3 V vs. $Li/Li^+$ and cyclic voltammetry (CV).

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Solid Solution and Defect Structure of LiCrO2 in the Pseudo-binary Systems : Li2Cr2O4-MgAl2O4 (의사이성분계, Li2Cr2O4-MgCr2O4와 Li2Cr2O4-MgAl2O4에서의 LiCrO2 고용체 형성과 결합구조)

  • 정영서;오근호;김호기
    • Journal of the Korean Ceramic Society
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    • v.25 no.1
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    • pp.35-41
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    • 1988
  • In the system of Li2O-MgO-Al2O3-Cr2O3, the crystalline solid solution of LiCrO2 along the pseudo-binary join between rocksalt structure(LiCrO2) and spinel structure(MgCr2O4 or MgAl2O4) have been investigated by x-ray diffraction techniques. In this study, order-disorder phase transition of LiCrO2 was observed and the unit cell of the disordered LiCrO2 structure has been established. It has been found that LiCrO2 makes a solid solution over a wide range with MgAl2O4, while not with MgCr2O4. This difference was explained as being due to the ability of oxygen lattice distortion which depended on the relative sizes and chemical bonding characteristics of the substituted ions.

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Preparation and Electrochemical Properties of LiFePO4-PSS Composite Cathode for Lithium-ion Batteries

  • Nguyen, Hiep Van;Jin, En Mei;Gu, Hal-Bon
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.4
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    • pp.177-180
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    • 2012
  • In this study, we prepared $LiFePO_4$- poly (sodium 4-styrenesulfonate) (PSS) composite by the hydrothermal method and ball-milling process. Different wt% PSS were added to $LiFePO_4$. The cathode electrodes were made from mixtures of $LiFePO_4$-PSS: SP-270: PVDF in a weighting ratio of 70%: 25%: 5%. $LiFePO_4$-PSS powders were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The electrochemical properties of $LiFePO_4$-PSS/Li batteries were analyzed by cyclic voltammetry, charge/discharge tests, and AC impedance spectroscopy. A Li/$LiFePO_4$-PSS battery with 4.75 wt% PSS shows the best electrochemical properties, with a discharge capacity of 128 mAh/g.