Enhanced rate performance of two-phase carbon coated LiFePO4/(C+G) using natural graphite as carbon source

The electrochemical performance of LiFePO4/C samples synthesized by different carbon sources varies considerably, the structural difference of residual carbon in LiFePO4/C accounts for the performance variation. Higher performance is associated with a larger ratio of graphitic carbon, which exhibits better electronic conductivity than amorphous carbon. To improve the electronic conductivity, we prepared LiFePO4/(C+G) composites by a one-step solid-state method, in which natural graphite is used as reducing agent and conducting additives. The samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM). Raman microprobe spectroscope and other electrochemical methods. The results show that reversible capacity and rate performance of LiFePO4 are improved considerably by the two-phase carbon coating. Therefore, LiFePO4/(C+G) composites are a promising candidate for lithium ion batteries. (C) 2011 Elsevier B.V. All rights reserved.