Reaction Mechanisms on Solvothermal Synthesis of Nano LiFePO₄ Crystals and Defect Analysis

A solvothermal process was used to synthesize LiFePO 4 nanomaterials for lithium ion batteries. Reaction parameters such as reaction temperature and residence time were explored to obtain the optimal LiFePO 4 sample. A three-stage reaction mechanism is proposed to better understand the solvothermal synthesis process. X-ray diffraction, scanning electron microscopy, and Fourier transform IR spectroscopy were used to investigate the prepared samples under different conditions. The LiFePO 4 formation reaction occurred at a temperature as low as 89 °C. Defect analysis results showed that after 4 h of solvothermal treatment the concentration of lithium vacancy and Li–Fe antisite defects was too low to be detected. The charge–discharge data of the obtained LiFePO 4 showed that the carbon-coated LiFePO 4 samples prepared at 180 °C after 4 h of solvothermal treatment had a discharge capacity of 160.6 mA h g –1 at a discharge rate of 0.1C and 129.6 mA h g –1 at 10C.