Abstract:

High-density LiFePO4/C composites were successfully synthesized by a solid state-carbothermal reduction method using Fe2O3 and citrate ferric as Fe3+ precursors in which the citrate acid radical acted as both reducing agent and carbon source. The reaction mechanism was investigated using thermogravimetric and differential scanning calorimetry (TG-DSC). The structures and physicochemical properties of the LiFePO4/C composites were characterized by X-ray diffraction, scanning electron microscopy, laser particle-size distribution measurement, tap-density testing and galvanostatic charge-discharge. Results indicated that the material calcined at 700 ℃ possessed a crystal olivine structure, a moderate particle size, excellent electrochemical performance and a high tap-density. It had a high initial discharge capacity of 129 mAh·g-1 at 17 mA·g-1 charge-discharge current density without decaying after twenty cycles. This material, which had a multi-peak particle size distribution, consisted of nanometer-sized and micrometer-sized particles and had high tap-density of 1.41 g·cm-3.

Key words: Li-ion battery, Cathode material, LiFePO4, Carbothermal reduction method, Citrate ferric