Effect of Vanadium Incorporation on Electrochemical Performance of LiFePO4 for Lithium-Ion Batteries

• Published in: Journal of physical chemistry. C 2011-07, Vol.115 (27), p.13520-13527
• Main Authors: Zhang, Lu-Lu, Liang, Gan, Ignatov, Alexander, Croft, Mark C, Xiong, Xiao-Qin, Hung, I-Ming, Huang, Yun-Hui, Hu, Xian-Luo, Zhang, Wu-Xing, Peng, Yun-Long
• Format: Article
• Language: English
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp2034906

A series of LiFe1–x V x PO4/C samples have been successfully prepared using a two-step solid-state reaction route. The effect of vanadium incorporation on the performance of LiFePO4 has systematically been investigated with X-ray diffraction, Raman spectroscopy, charge/discharge measurements, and cyclic voltammetry tests. It is found that V incorporation significantly enhances the electrochemical performance of LiFePO4. Particularly, the LiFePO4/C sample with 5 at. % vanadium doping exhibits the best performance with a specific discharge capacity of 129 mAh g–1 at 5.0 C after 50 cycles; the capacity retention ratio is higher than 97.5% at all C rates from 0.1 to 5.0 C. X-ray absorption spectroscopy results show that the valence of V in LiFe0.95V0.05PO4/C is between +3 and +4. It is confirmed that the samples with x ≤ 0.03 are in single phase, whereas the samples with 0.05 ≤ x < 1.00 contain two impurity phases: Li3V2(PO4)3 and LiVOPO4. A clear feature of vanadium incorporation in LiFePO4 has been specified.