Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (5): 866-872.doi: 10.3866/PKU.WHXB201403041

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Vacuum-Assisted Synthesis of Fe3(PO4)2·8H2O and Its Influence on Structure, Morphology and Electrochemical Performance of LiFePO4/C

REN Jian-Xin1, HU You-Kun1, 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 610065, P. R. China
  • Received:2013-12-16 Revised:2014-03-04 Published:2014-04-25
  • Supported by:

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

Abstract:

A vacuum-assisted precipitation method was used to synthesize Fe3(PO4)2·8H2O (FP). The FP was then used to synthesize carbon-coated LiFePO4 (LFP/C) particles. The influence of FP on the structure, morphology, and electrochemical performance of LFP was investigated. The X-ray diffraction (XRD) patterns and molar ratio of Fe to P showed that the FP which was produced using a vacuum-assisted method was of high purity and gave highly crystalline, impurity-free LFP. Scanning electron microscopy (SEM) showed that the FP contained undeveloped particles. The undeveloped FP results in uniform LFP/C particles, without agglomeration. Transmission electron microscopy (TEM) showed that the LFP particles were coated with a homogeneous carbon layer. The LFP/C showed excellent discharge capacities of 140, 113, and 100 mAh·g-1 at 1C, 10C, and 20C rates, respectively. The cyclic voltammograms (CVs) of LFP showed a low polarization voltage and sharp redox peaks. The charge-discharge platform curves showed that LFP had an excellent high-rate capability. Electrochemical impedance spectroscopy (EIS) tests showed that the lithium-ion diffusion coefficients of LFP/C produced with and without vacuum assistance were 1.42×10-13 and 4.22×10-14 cm2·s-1, respectively, proving that vacuum assistance can improve the diffusion coefficients of LFP/C.

Key words: Fe3(PO42·, 8H2O, LiFePO4/C, Vacuum-assistance, Precipitation, High rate

MSC2000: 

  • O646