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

Title
Comparative studies on C-coated and uncoated LiFePO4 cycling at various rates and temperatures using synchrotron based in situ X-ray diffraction
Authors
신호철남경완장원영조병원윤원섭Xiao-Qing Yang정경윤
Keywords
LiFePO4; In situ X-ray diffraction; Low temperature performance; Rate performance; Lithium secondary batteries
Issue Date
2011-01
Publisher
Electrochimica acta
Citation
VOL 56, NO 3, 1182-1189
Abstract
The structural changes of LiFePO4 and C-coated LiFePO4 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 4.5V due to the larger polarization when charged at −20 ◦C.
URI
http://pubs.kist.re.kr/handle/201004/39762
ISSN
0013-4686
Appears in Collections:
KIST Publication > Article
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