Preparation and electrochemical performance of Gd-doped LiFePO4/C composites

In this paper, LiFe1-x GdxPO4/C composites (x = 0, 0.02, 0.04, 0.06, 0.07, 0.08) are synthesized via a high-temperature solid-phase reaction. The structure and electrochemical behavior of the materials are investigated using a wide range of techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), particle size analysis, galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). It is found that the maximum discharge capacity of the as-prepared LiFe0.93Gd0.07PO4/C composite can reach up to 150.7 mAh g(-1), 125.9 mAh g(-1), 106.0 mAh g(-1) and 81.3 mAh g(-1) at rates of 0.2 C, 1C, 5C and 10 C, respectively. And at 0.1 C rate, the initial discharge capacity of the composite monotonically increases with temperature from 66.3 to 122.2 mAh g(-1) in the range of -30 to 0 degrees C. It is also demonstrated that the presence of a small amount of Gd3+ ion in the sample prepared in this work can reduce the charge-transfer resistance, resulting in the enhanced electrochemical catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.