• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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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.

• Transactions on Electrical and Electronic Materials
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• 제8권1호
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.241-242
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• 2006

In this work, the $LiFePO_4-LiCoO_2$ mixed cathode electrodes were prepared and their electrochemical performances were measured in different current density. The cell of $LiFePO_4-LiCoO_2$ observed two voltage plateau regions at 3.4 and 3.9V. The cell of $LiFePO_4-LiCoO_2$ (90:10 wt%) mixed cathode delivered a discharge capacity of ca. 139.8 mAh/g at a 0.2C rate. The capacity of the cell decreased with the current rate and a useful capacity of ca 85.7mAh/g was obtained at a 2C rate.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.79-88
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• 2013

$LiFePO_4$ is a promising active material (AM) suitable for use in high performance lithium-ion batteries used in automotive applications that require high current capabilities and a high degree of safety and reliability. In this study, an optimization of the electrode design parameters was performed to produce high capacity lithium-ion batteries based on $LiFePO_4$/graphite electrodes. The electrode thickness and porosity (AM density) are the two most important design parameters influencing the cell capacity. We quantified the effects of cathode thickness and porosity ($LiFePO_4$ electrode) on cell performance using a detailed one-dimensional electrochemical model. In addition, the effects of those parameters were experimentally studied through various coin cell tests. Based on the numerical and experimental results, the optimal ranges for the electrode thickness and porosity were determined to maximize the cell capacity of the $LiFePO_4$/graphite lithium-ion batteries.

• Korean Chemical Engineering Research
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• 제57권4호
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• pp.547-552
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• 2019

Electrochemical properties of $LiMn_{0.8}Fe_{0.2}PO_4$ cathode were investigated with gel polymer electrolyte (GPE). To access fast and efficient transport of ions and electrons during the charge/discharge process, a pure and well-crystallized $LiMn_{0.8}Fe_{0.2}PO_4$ cathode material was directly synthesized via spray-pyrolysis method. For high operation voltage, polyacrylonitrile (PAN)-based gel polymer electrolyte was then prepared by electrospinning process. The gel polymer electrolyte showed high ionic conductivity of $2.9{\times}10^{-3}S\;cm^{-1}$ at $25^{\circ}C$ and good electrochemical stability. $Li/GEP/LiMn_{0.8}Fe_{0.2}PO_4$ cell delivered a discharge capacity of $159mAh\;g^{-1}$ at 0.1 C rate that was close to the theoretical value ($170mAh\;g^{-1}$). The cell allows stable cycle performance (99.3% capacity retention) with discharge capacity of $133.5mAh\;g^{-1}$ for over 300 cycles at 1 C rate and exhibits high rate-capability. PAN-based gel polymer is a suitable electrolyte for application in $LiMn_{0.8}Fe_{0.2}PO_4/Li$ batteries with perspective in high energy density and safety.

• 한국광물학회지
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• 제26권1호
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• pp.35-44
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• 2013

유사 올리빈 구조를 가지는 탄소코팅 합성 $Li^+Fe^{2+}(PO_4)^{3-}$ 분말시료에 대한 상온-고압실험을 대칭 다이아몬드 앤빌기기를 이용하여 35.0 GPa까지 시행하였다. $LiFePO_4$의 압축 데이터를 이용하여 계산된 체적탄성률은 $130.1{\pm}10.3$ GPa이다. 18 GPa 이상의 압력에서 d = 3.386 ${\AA}$ 위치에 새로운 피크가 관찰되고 35 GPa에서는 d = 2.854 ${\AA}$에 또 다른 피크가 관찰되고 있으나 주 결정구조는 사방정계인 것으로 판단된다. 압력에 대한 단위 포 부피의 압축은 M1($Li^+O_6$)의 수축이 두드러지고 M2($Fe^{2+}O_6$)와 사면체($PO_4$)의 수축은 상대적으로 작은 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.852-856
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• 2011

The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped $LiFePO_4$ were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with $LiFePO_4$ cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped $LiFePO_4$ resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.303-303
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• 2008

$LiMn_2O_4$는 출력특성이 좋고 가격이 저렴하지만 전해액 중에서 $Mn^{2+}$이 용출되어 나오는 것과 반복적인 충방전시 구조가 파괴되는 단점이 있어 이것을 보완하고자 $FePO_4\cdot2H_2O$를 $LiMn_2O_4$의 표면에 코팅하였다, $LiMn_2O_4$를 모재로, $FePO_4\cdot2H_2O$를 코팅재로 사용하여 $FePO_4\cdot2H_2O$의 코팅량 변화와, 열처리 온도변화에 따른 물성 변화를살펴보았다, LiOH 와 $MnO_2$의 혼합물을 $1000^{\circ}C$ 에서 소성하여 $LiMn_2O_4$를 합성하고, Fe$(NO_3)_3$ 수용액과 $NH_4H_2PO_4$ 수용액을 혼합하여 $FePO_4\cdot2H_2O$를 제조하였다, $LiMn_2O_4$에 $FePO_4\cdot2H_2O$를 1wt%, 2wt%, 3wt% 비율로 ball milling 을 통해 코팅한 후, 온도를 변화시키면서 열처리 하였다. 코팅한 물질을 XRD를 통해 구조를 분석하고 SEM을 이용하여 형상을 관찰하였다. 또한 고온에서의 $Mn^{2+}$의 용출량을 ICP로 측정하고 half-cell을 만들어 충방전 test를 통해 충방전 특성을 조사하였다. 아울러, 코팅량과 열처리 온도 등 합성변수들이 소재특성 및 전기화학적 특성에 미치는 영향을 조사하였다.

• Journal of Electrochemical Science and Technology
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• 제4권3호
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.