Influence of carbon sources on electrochemical performances of LiFePO4/C composites

LiFePO4/C was synthesized via a solid-state reaction under N-2 atmosphere, and the reaction precursor was prepared by a sol-get method. The XRD results prove that the sintering temperature and carbon source have played a very important role in the crystallinity of LiFePO4/C composite. Complete crystallization occurred in the temperature range of 650-700 degrees C. The X-ray diffraction intensity of LiFePO4/C composite dropped, when the carbon source content was beyond 20%. The particles of synthesized LiFePO4/C were fine and homogeneous in size, with an average diameter of 100 nm. Charge-discharge tests were done with the synthesized LiFePO4/C served as cathode materials. It was found that the carbon source has a close relation to the initial discharge capacity of the composites. At a discharge rate of 0.1 C, the initial discharge capacities were 125.3, 133.3 and 155.0 mAh center dot g(-1) with the 20% content of acetylene black, sucrose and glucose as the carbon sources respectively. The LiFePO4/C composite prepared with glucose as the carbon source exhibited excellent large current charge-discharge properties. At discharge rates of 1 C and 3 C, the initial discharge capacities were 90% and 80%, respectively of that at 0.1 C. (C) 2008 Elsevier B.V. All rights reserved.