Synthesis and electrochemical performance of lithium iron phosphate/carbon composites based on controlling the secondary morphology of precursors

In this study, dihydrate iron phosphates with primary and secondary morphology were first prepared with ferric sulfate and phosphoric acid as the major raw materials, which were then taken as the precursor to prepare carbon-coated lithium iron phosphate composite material. Results show that structures of synthesized lithium iron phosphate/Carbon materials are the same, however, the morphologies are significantly different, especially the one synthesized with the secondary morphology iron phosphate precursor. Thus, the particle size, specific surface area and carbon coating effect of the material are changed accordingly, which can affect the electrochemical performance of the composite. The lithium iron phosphate/Carbon synthesized with spherical aggregation morphology (secondary morphology) iron phosphate precursor showed the best electrochemical property. At 0.5C and 10C rates, the first specific discharge capacity is 155.6 and 103.8 mA h/g respectively, which is better than that prepared with cabbage shape aggregation morphology (secondary morphology) and near-spherical simplex (primary morphology), increasing 1.38%, 1.37% and 3.58%, 9.05%, respectively. This research result provided new thoughts to further improve the electrochemical property of lithium iron phosphate/Carbon composites.