Synthesis and Characterization of LiFePO₄/C Cathode Materials by Sol–Gel Method

The carbon coated LiFePO₄ cathode materials (LiFePO₄/C) were successfully synthesized by sol–gel method with glucose, citric acid and PEG-4000 as dispersant and carbon source, respectively. The microstructure and grain size of LiFePO₄/C composite were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy. The results showed that the carbon source and calcination temperature had important effect on the graphitization degree of carbon; the carbon decomposed by citric acid had higher graphitization degree; with calcination temperature rising, the graphitization degree of carbon increased and the particles size increased. The graphitization degree and grain size were very important for improving the electrochemical performance of LiFePO₄ cathode materials, according to the experimental results, the sample LFP-700 (LFP-C) which was synthesized with citric acid as dispersant at 700 °C had lower polarization and larger discharge capacity.