Effect of carbon content and calcination temperature on the electrochemical performance of lithium iron phosphate/carbon composites as cathode materials for lithium-ion batteries

Lithium iron phosphate/carbon (LiFePO4/C) composites were prepared by a convenient method with water-soluble phenol-formaldehyde resin as the carbon precursor. The morphology, crystalline structure, thermal stability, and composition of as-prepared LiFePO4/C composites were investigated by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and Raman spectrometry. Their electrochemical performance was examined based on cyclic voltammogram with a LAND battery testing system while the effect of carbon content and calcination temperature was highlighted. Results show that carbon content and calcination temperature dramatically influence the discharge capacities and rate performance of LiFePO4/C composites. The optimal calcination temperature is 700 °C, and the optimal carbon content (mass fraction) is 8.7%. The LiFePO4/C composite prepared under the optimal conditions exhibits an initial room temperature discharge capacity of 150.2 mA h g−1 at a 0.2 C rate and a constant discharge capacity of about 105.7 mA h g−1 at a 20.0 C rate after 50 cycles, showing promising potential as a novel cathode material for lithium ion batteries.