Effects of different iron sources on the performance of LiFePO₄/C composite cathode materials

Olivine LiFePO₄/C composite cathode materials were synthesized by a solid state method in N₂ + 5vol% H₂ atmosphere. The effects of different iron sources, including Fe(OH)₃ and FeC₂O₄·2H₂O, on the performance of as-synthesized cathode materials were investigated and the causes were also analyzed. The crystal structure, the morphology, and the electrochemical performance of the prepared samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), laser particle-size distribution measurement, and other electrochemical techniques. The results demonstrate that the LiFePO₄/C materials obtained from Fe(OH)₃ at 800℃ and FeC₂O₄·2H₂O at 700℃ have the similar electrochemical performances. The initial discharge capacities of LiFePO₄/C synthesized from Fe(OH)3 and FeC₂O₄·2H₂O are 134.5 mAh.g^-1 and 137.4 mAh.g^-1 at the C/5 rate, respectively. However, the tap density of the LiFePO₄/C materials obtained from Fe(OH)₃ are higher, which is significant for the improvement of the capacity of the battery.