• Title/Summary/Keyword: LiFePO4

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Surface Treatment of LiFePo4 Cathode Material for Lithium Secondary Battery

  • Son, Jong-Tae
    • Journal of the Korean Electrochemical Society
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    • v.13 no.4
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    • pp.246-250
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    • 2010
  • In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

The Advanced Research on Electrochemical Properties of $LiFePO_4$ Cathode Materials for Lithium Polymer Batteries. (리튬폴리머전지용 정극활물질 $LiFePO_4$의 전기화학적 특성 향상 연구)

  • Jun, Dae-Kyoo;Jin, En-Mei;Han, Zhen-Ji;Baek, Hyung-Ryul;Gu, Hal-Bon;Park, Bok-Kee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.06a
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    • pp.368-369
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    • 2006
  • The pure $LiFePO_4$, carbon added $LiFePO_4(LiFePO_4/C$) and pyrene added $LiFePO_4(LiFePO_4/P$) are synthesized by using solid-state reaction. XRD patterns show no impurity phase in the three kinds of the cathode materials. The 10wt% pyrene added $LiFePO_4$ shows around 140mAh/g of discharge capacity at 3rd cycle compared to the pure $LiFePO_4$. The carbon added $LiFePO_4$ shows 145mAh/g of discharge capacity at 3rd cycle and stable cycle-life compared to the others.

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Electrochemical Characteristics of Carbon-coated LiFePO4 as a Cathode Material for Lithium Ion Secondary Batteries

  • Shin, Ho-Chul;Lee, Byung-Jo;Cho, Won-Il;Cho, Byung-Won;Jang, Ho
    • Journal of the Korean Electrochemical Society
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    • v.8 no.4
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    • pp.168-171
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    • 2005
  • The electrochemical properties of $LiFePO_4$ as a cathode for Li-ion batteries were improved by incorporating conductive carbon into the $LiFePO_4$. X-ray diffraction analysis and SEM observations revealed that the carbon-coated $LiFePO_4$ consisted of fine single crystalline particles, which were smaller than the bare $LiFePO_4$. The electrochemical performance of the carbon-coated $LiFePO_4$ was tested under various conditions. The carbon-coated $LiFePO_4$ showed much better performance in terms of the discharge capacity and cycling stability than the bare $LiFePO_4$. The improved electrochemical performances were found to be attributed to the reduced particle size and enhanced electrical conductivity of the $LiFePO_4$ by the carbon.

Li Ion Diffusivity and Improved Electrochemical Performances of the Carbon Coated LiFePO4

  • Park, Chang-Kyoo;Park, Sung-Bin;Oh, Si-Hyung;Jang, Ho;Cho, Won-Il
    • Bulletin of the Korean Chemical Society
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    • v.32 no.3
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    • pp.836-840
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    • 2011
  • This study examines the effects of a carbon coating on the electrochemical performances of $LiFePO_4$. The results show that the capacity of bare $LiFePO_4$ decreased sharply, whereas the $LiFePO_4$/C shows a well maintained initial capacity. The Li ion diffusivity of the bare and carbon coated $LiFePO_4$ is calculated using cyclic voltammetry (CV) to determine the correlation between the electrochemical performance of $LiFePO_4$ and Li diffusion. The diffusion constants for $LiFePO_4$ and $LiFePO_4$/C measured from CV are $6.56{\times}10^{-16}$ and $2.48{\times}10^{-15}\;cm^2\;s^{-1}$, respectively, indicating considerable increases in diffusivity after modifications. The Li ion diffusivity (DLi) values as a function of the lithium content in the cathode are estimated by electrochemical impedance spectroscopy (EIS). The effects of the carbon coating as well as the mechanisms for the improved electrochemical performances after modification are discussed based on the diffusivity data.

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.

Effects of doping on the electrical conductivity and particle size in olivine type $LiFePO_4$ powders (올리빈형 $LiFePO_4$ 분말의 전기전도도와 입도 크기에 미치는 도핑의 영향)

  • Bai, Jin-Tao;Ha, Jung-Soo;Kim, Chang-Sam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.18 no.6
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    • pp.248-252
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    • 2008
  • To get a fine $LiFePO_4$ powder with high electrical conductivity, the influences of doping of aliovalent elements(Cr+B and Cr+Al) on electrical conductivity and of heat treatment conditions on particle size of the doped powders were studied. Two kinds of the doped powders $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.065}Cr_{0.03}Al_{0.005}PO_4$ were synthesized using mechanochemical milling and subsequent heat treatment at $675{\sim}750^{\circ}C$ for $5{\sim}10\;h$. The doping enhanced grain growth and electrical conductivity. The electrical conductivity at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$ in the doped with Cr and Al, and $5{\times}10^{-10}S/cm$ in the undoped one.

Re-synthesis and Electrochemical Characteristics of LiFePO4 Cathode Materials Recycled from Scrap Electrodes

  • Kim, Hyung Sun;Shin, Eun Jung
    • Bulletin of the Korean Chemical Society
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    • v.34 no.3
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    • pp.851-855
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    • 2013
  • This paper describes an environmentally friendly process for the recovery of $LiFePO_4$ cathode materials from scrap electrodes by a simple thermal treatment method. The active materials were easily separated from the aluminum substrate foil and polymeric binders were also decomposed at different temperatures ($400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$) for 30 min under nitrogen gas flow. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), Raman spectroscopy, Thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The electrochemical properties of the recycled $LiFePO_4$ cathode were evaluated by galvanostatic charge and discharge modes. The specific charge/discharge capacities of the recycled $LiFePO_4$ cathode were similar to those of the original $LiFePO_4$ cathode. The $LiFePO_4$ cathode material recovered at $500^{\circ}C$ exhibits a somewhat higher capacity than those of other recovered materials at high current rates. The recycled $LiFePO_4$ cathode also showed a good cycling performance.

The Root Cause of the Rate Performance Improvement After Metal Doping: A Case Study of LiFePO4

  • Park, Chang-Kyoo;Park, Sung-Bin;Park, Ji-Hun;Shin, Ho-Chul;Cho, Won-Il;Jang, Ho
    • Bulletin of the Korean Chemical Society
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    • v.32 no.3
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    • pp.921-926
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    • 2011
  • This study investigates a root cause of the improved rate performance of $LiFePO_4$ after metal doping to Fesites. This is because the metal doped $LiFePO_4$/C maintains its initial capacity at higher C-rates than undoped one. Using $LiFePO_4$/C and doped $LiFe_{0.97}M_{0.03}PO_4$/C (M=$Al^{3+}$, $Cr^{3+}$, $Zr^{4+}$), which are synthesized by a mechanochemical process followed by one-step heat treatment, the Li content before and after chemical delithiation in the $LiFePO_4$/C and the binding energy are compared using atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS). The results from AAS and XPS indicate that the low Li content of the metal doped $LiFePO_4$/C after chemical delithiation is attributed to the low binding energy induced by weak Li-O interactions. The improved capacity retention of the doped $LiFePO_4$/C at high discharge rates is, therefore, achieved by relatively low binding energy between Li and O ions, which leads to fast Li diffusivity.

Electrochemical Properties of LiMPO4(M = Fe, Mn) Synthesized by Sol-Gel Method (졸-겔법에 의해 제조된 LiMPO4(M = Fe, Mn) 양극 활물질의 전기화학적 특성)

  • Kim, Jae-Kwang;Baek, Dong-Ho;Shin, Yong-Jo;Ahn, Jou-Hyeon;Seo, Yang-Gon;Kim, Chi-Su;Yoon, Seok-Jun;Cho, Myung-Hun
    • Journal of the Korean Electrochemical Society
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    • v.11 no.2
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    • pp.120-124
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    • 2008
  • Carbon-coated $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ cathode materials for lithium batteries were synthesized by a sol-gel method. X-ray diffraction and scanning electron microscopy data showed that the cathode materials are pure crystalline and are surrounded by porous carbon. The initial discharge capacities of $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ with the liquid electrolyte of 1M $LiPF_6$ in EC/DMC are 132 mAh/g and 145 mAh/g, respectively, at current density of 0.1 C-rate. $LiFePO_4$ and $LiMn_{0.4}Fe_{0.6}PO_4$ with an electrospun polymer-based electrolyte exhibit initial discharge capacities of 114 and 130 mAh/g at 0.1 C-rate at room temperature, respectively.

The electrochemical properties of $LiFe_xMn_{1-x}PO_4$ cathode materials for lithium polymer batteries (리튬 폴리머 전지용 $LiFe_xMn_{1-x}PO_4$ 정극활물질의 전기화학적 특성)

  • Jun, Dae-Kyoo;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.424-425
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    • 2005
  • The purpose of this study is to research and develop $LiFe_xMn_{1-x}PO_4$ cathode for lithium polymer batteries. $LiFe_xMn_{1-x}PO_4$ cathode active materials were prepared using a solid-state reaction by adding carbon black to the synthetic precursors. We investigated cyclic voltammetry and charge/discharge cycling of $LiFe_xMn_{1-x}PO_4$/SPE/Li cells. The discharge capacity of $LiFe_{0.5}Mn_{0.5}PO_4$ was l26mAh/g and 110mAh/g at 1st and 10th cycle.

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