Abstract
LiFePO4 powders were synthesized by the semi-solid-state method. Different from the traditional solid state method, this method combined a precipitation method with a post heat treatment. The self-assembled Fe precursor precipitates had a specialized morphology, which was unique. The mixture obtained by uniformly mixed the Fe precursor with sucrose was heat treated under 600-800℃ for the synthesis of LiFePO4/C. To optimize the carbon coating in the LiFePO4 powders, various amounts of carbon was added to the mixture prior to the high temperature treatment. It was found that sample with 15% sucrose addition sintered at 750℃ for 3 hours had a better carbon coating. Carbon here acted as a reducing agent to prevent divalent iron ions from oxidation, and the carbon coating on the LiFePO4 particles enhance the electronic conductivity. Moreover, carbon could suppress particles from growing at high temperature. LiFePO4/C doped with metal (eg. Mg doping) can also increase the electronic conductivity. In addition, it had higher surface area than LiFePO4/C without doping.