Comparative studies on C-coated and uncoated LiFePO4 cycling at various rates and temperatures using synchrotron based in situ X-ray diffraction
- Comparative studies on C-coated and uncoated LiFePO4 cycling at various rates and temperatures using synchrotron based in situ X-ray diffraction
- 신호철; 남경완; 장원영; 조병원; 윤원섭; Xiao-Qing Yang; 정경윤
- LiFePO4; In situ X-ray diffraction; Low temperature performance; Rate performance; Lithium secondary batteries
- Issue Date
- Electrochimica acta
- VOL 56, NO 3, 1182-1189
- 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.
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