Effect of Calcination Temperature on the Compositions and Electrochemical Performance of Products in the Synthesis of LiFePO_4

LiFePO4/C composite cathode materials were synthesized by carbothermal reduction(CTR)method using FePO4 as precursor.The precursors and the products were characterized by TG-DTA,FTIR,XRD,and the reaction mechanism was investigated.The compositions and electrochemical performance of the products at different calcination temperatures were studied.The results showed that LiFePO4 in the sample prepared at 300 ℃ was primary phase,so the crystallization temperature in this route was lower than that of other methods.At 300,400,500 ℃,Li3PO4 and Fe2O3 as impurity phases existed in the samples and the higher temperature led to less impurity phases.The sample calcined at 600 ℃ had no impurity,but Li4P2O7 appeared at 700 ℃.The sample prepared at 600 ℃ for 24 h had the best electrochemical performance,which could deliver a discharge capacity of 146 mAh·g-1 at 0.1C and retain a discharge capacity of 141 mAh·g-1 after 15 cycles.