Acta Phys. -Chim. Sin. ›› 2009, Vol. 25 ›› Issue (09): 1916-1920.doi: 10.3866/PKU.WHXB20090929

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A Coalescence Mechanism for the Composite Cathode Material xLiFePO4·yLi3V2(PO4)3

ZHENG Jun-Chao, LI Xin-Hai, WANG Zhi-Xing, LI Jin-Hui, WU Ling, LI Ling-Jun, GUO Hua-Jun   

  1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, P. R. China|School of Materials and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi Province, P. R. China
  • Received:2009-04-17 Revised:2009-06-12 Published:2009-09-03
  • Contact: LI Xin-Hai E-mail:tonyson_011@163.com

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Abstract:

Composite cathode material xLiFePO4·yLi3V2(PO4)3 was obtained from wet chemical reduction and lithiation method by using FePO4·xH2O, V2O5, NH4H2PO4, Li2CO3 as raw materials and oxalic acid as reductant. X-ray diffraction (XRD) results showed that the composite material contained olivine LiFePO4 and monoclinic Li3V2(PO4)3 phases. High resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometry (EDAX) results indicated that some LiFePO4 and Li3V2(PO4)3 in the composite material were doped by V and Fe, respectively, and formed a solid solution. The valences of Fe and V doping in Li3V2(PO4)3 and LiFePO4 are +2 and +3, respectively. Charge and discharge tests showed that the synthesized composite material exhibited better electrochemical performance than individual LiFePO4 and Li3V2(PO4)3. Cyclic voltammetry indicated the composite material showing good lithium ions extraction/insertion property.

Key words: Lithium ion battery, Composite cathode material, Doping, xLiFePO4·yLi3V2(PO4)3