Preparation of lithium iron phosphate with superior electrochemical performances from titanium white by-product ferrous sulfate

In this paper, FePO₄∙2H₂O and FePO₄ have been successfully accomplished by utilizing titanium white by-product ferrous sulfate via two-step synthesis method, which is further employed to react with Li₂CO₃ via carbothermal reduction to prepare LiFePO₄ cathode materials. The composition and structure characteristics of obtained samples are studied in detail by TG-DSC, XRD, XPS, FESEM and TEM, and the electrochemical performances of prepared LiFePO₄ are also carefully investigated. The results indicate that the discharge specific capacity of LiFePO₄ synthesized from FePO₄ achieves 162.4 and 153.7 mAh∙g⁻¹ at 0.1C and 1C, which is 2.2 and 2.9 mAh∙g⁻¹ higher than that from FePO₄∙2H₂O, and the capacity retention rate reaches as high as 97.5 % after 450 cycles at 1C, correspondingly 94.8 % for LiFePO₄ from FePO₄∙2H₂O. It is mainly ascribed to the smaller particle size of LiFePO₄ synthesized from FePO₄, and the intimately ordered interface structure between the carbon layer and LiFePO₄, which greatly promotes the migration of lithium ions in the lithiation and delithiation process.