Comparative studies on C-coated and uncoated LiFePO4 cycling at various rates and temperatures using synchrotron based in situ X-ray diffraction

Ho Chul Shin, Kyung Wan Nam, Won Young Chang, Byung Won Cho, Won Sub Yoon, Xiao Qing Yang, Kyung Yoon Chung

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

The structural changes of LiFePO4 and C-coated LiFePO 4 during charging at various C-rates and temperatures are investigated using synchrotron based in situ X-ray diffraction technique. The XRD patterns collected during cycling show the structural evidence of the positive effects of carbon coating on LiFePO4 for the electrochemical performance improvements at different temperatures, especially at low temperatures. At -10 °C, the C-coated LiFePO4 shows comparable capacities with the sample cycled at room temperature when cycled at C/5 rate with a slight shift of the plateau to a higher voltage during charging. The in situ XRD patterns collected simultaneously show a complete phase transformation from triphylite to heterosite. At -20 °C, the C-coated LiFePO4 delivers 55.6% of its theoretical capacities at C/5 rate. However, the plateau in the charging curve becomes sloppy and shifts to a higher voltage. The in situ XRD patterns show that the phase transformation from triphylite to heterosite is not completed when charged to 4.5 V due to the larger polarization when charged at -20 °C.

Original languageEnglish
Pages (from-to)1182-1189
Number of pages8
JournalElectrochimica Acta
Volume56
Issue number3
DOIs
StatePublished - 1 Jan 2011

Keywords

  • In situ X-ray diffraction
  • LiFePO
  • Lithium secondary batteries
  • Low temperature performance
  • Rate performance

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