Effects of solid phase reaction conditions on electrochemical performance of lithium iron phosphate

The lithium iron phosphate in olivine crystal structure was prepared by solid phase reaction method, using lithium carbonate(Li₂CO₃) as the lithium source, ammonium dihydrogen phosphate(NH₄H₂PO₄) as the phosphorus source, ferrous oxalate(FeC₂O₄·2H₂ O) as the iron source, and citric acid(C₆H₈O₇·H₂O) the carbon source. The phase composition, structure, morphology, and electrochemical properties of the synthesized lithium iron phosphate material were characterized by X-ray diffractometer(XRD), scanning electron microscope(SEM), energy dispersive spectroscope(EDS), specific surface area analyzer(BET), and electrochemical test. The effects of calcination temperature and holding time in solid phase reaction on the electrochemical performance of lithium iron phosphate were investigated, and the synthesized samples were modified by carbon coating. The results show that the lithium iron phosphate cathode material prepared at the calcination temperature of 700 ℃ and the holding time of 12 h has the best electrochemical performance and the carbon coating can effectively improve the performance of the electrode material. The lithium iron phosphate electrode material coated with carbon has a first discharge specific capacity of 319.2 mAh·g^-1 at a charging current density of 0.2 C. After circulating 100 times at a charging current density of 1 C, the discharge specific capacity is maintained at 168.1 mAh·g^-1.