Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (1): 75-82.doi: 10.3866/PKU.WHXB201311261

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Synthesis of Rod-Like LiFePO4/C Materials with Different Aspect Ratios by Polyol Process

HU You-Kun1, REN Jian-Xin1, WEI Qiao-Ling1,3, GUO Xiao-Dong1, TANG Yan1, ZHONG Ben-He1, LIU Heng2   

  1. 1 College of Chemical Engineering, Sichuan University, Chengdu 610065, P. R. China;
    2 College of Materials Science and Engineering, Sichuan University, Chengdu 610064, P. R. China;
    3 Department of Chemical Engineering, Tsinghua University, Beijing 100084, P. R. China
  • Received:2013-08-11 Revised:2013-11-25 Published:2014-01-01
  • Contact: GUO Xiao-Dong E-mail:xiaodong2009@scu.edu.cn
  • Supported by:

    The project was supported by the Sichuan University Funds for Young Scientists, China (2011SCU11081) and Research Fund for the Doctoral Program of Higher Education, Ministry of Education, China (20120181120103).

Abstract:

Rod-like LiFePO4/C particles with different aspect ratios were synthesized by controlling the reflux reaction time in polyol medium at a low temperature, using an Fe3+ salt as the iron source. The precursors and final LiFePO4/C samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge test. The results show that the reflux reaction time has a significant effect on the characteristics of the LiFePO4 precursors and electrochemical performance of the final LiFePO4/C samples. The morphology of the precursors is transformed from irregular short rod-like particles into regular long rod-like particles, and the aspect ratios of the rods increase with increasing reflux reaction time from 4 to 16 h. At a reflux reaction time of 10 h, the material contains multifarious morphologies, which is beneficial to the electron transmission, and displays an excellent electrochemical performance at low discharge rates, the discharge capacity is 163 mAh·g-1 at 0.1C rate. Extension of the reflux reaction time to 16 h, the material reveals the biggest aspect ratio, which is conducive to the diffusion of lithium ions, and gives good electrochemical performance at high discharge rates, the discharge capacities are measured to be 135, 125, 118, 110, and 98 mAh·g-1 at 1C, 3C, 5C, 10C, and 20C rates, respectively, revealing good cycling performance and little capacity fading.

Key words: LiFePO4, Lithium-ion battery, Polyol process, Triethylene glycol, Reflux reaction time

MSC2000: 

  • O646