Influence of carbon sources on LiFePO4/C composites synthesized by the high-temperature high-energy ball milling method

Carbon-coated LiFePO4 composites were synthesized by a new method of high-temperature high-energy ball milling (HTHEBM). Fe2O3 and LiH2PO4 were used as raw materials. Glucose, sucrose, citric acid and active carbon were used as reducing agents and carbon sources, respectively. In this method, high-energy ball milling and carbon coating worked together and, therefore, fine and homogeneous LiFePO4/C particles with excellent properties were obtained in a relatively short synthesis time of 9 h. Moreover, the synthesis process could be completely finished at a relatively lower temperature of 600 °C for high-energy ball milling transforming mechanical energy into thermal energy. The results of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical performance tests indicated that carbon source had an important influence on the properties of LiFePO4/C composites synthesized by the HTHEBM method. It was proved that the LiFePO4 composites coated with glucose had the best properties with 1 μm geometric mean diameter and 150.3 mA h g−1 initial discharge capacity at a current rate of 0.1 C. After the 20th cycle test, the reversible capacity was 148 mA h g−1 at 0.1 C, showing a retention ratio to the initial capacity of 98.5%.