Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (07): 1507-1514.doi: 10.3866/PKU.WHXB201304231

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Synthesis and Electrochemical Properties of LiFe1-xNbxPO4/C Composite Cathode Material by Two-Step Synthesis Route

CAO Yan-Bing1,2, LUO Liang1, DU Ke1, PENG Zhong-Dong1, HU Guo-Rong1, JIANG Feng2   

  1. 1 School of Metallurgical Science and Engineering, Central South University, Changsha 410083;
    2 School of Materials Science and Engineering, Central South University, Changsha 410083
  • Received:2013-01-18 Revised:2013-04-19 Published:2013-06-14
  • Contact: PENG Zhong-Dong E-mail:cybcsu@csu.edu.cn
  • Supported by:

    The project was supported by the National Key Technology R&D Program of China (2007BAE12B01), Fundamental Research Funds for the Central Universities, China (2012QNZT018), China Postdoctoral Science Foundation (2012M521546), and Postdoctoral Science Foundation of Central South University, China.

Abstract:

LiFePO4/C composite was prepared by two-step synthesis route, with LiH2PO4 and FeC2O4· 2H2O as starting materials. In the process, the carbon sources polyvinyl alcohol (PVA) and glucose were added in a stepwise fashion. The well-crystallized LiFePO4/C composite with homogeneous small particles was obtained after reacting at 700℃ for 4 h. This composite had a discharge specific capacity of 157.3 mAh·g-1 at 0.1C rate and 138.4 mAh·g-1 at 1C rate. On the basis of carbon coating modification, Nb-ion-doped LiFe1-xNbxPO4/C (x=0.005, 0.01, 0.015, 0.02) composites were prepared. The optimized LiFe0.99Nb0.01PO4/C cathode displayed a discharge specific capacity 160.5 mAh·g-1 at 0.1C discharge rate, 136.0 mAh·g-1 at 5C and maintained 134.8 mAh·g-1 after 50 cycles, showing good rate properties and cycling stability. Cyclic voltammetry (CV) measurements indicated that aliovalent dopant substituting on the Fe sites can reduce the resistance of Li ion diffusion in the electrode process, increase phase transformation kinetics during cycling, and enhance the reversibility of LiFePO4 electrodes.

Key words: Polyanion cathode material, LiFePO4, Two-step synthesis, Nb doping

MSC2000: 

  • O646