Synthesis of LiFePO4/C cathode material from ferric oxide and organic lithium salts

LiFePO4/C cathode material has been simply synthesized via a modified in situ solid-state reaction route using the raw materials of Fe2O3, NH4H2PO4, Li2C2O4 and lithium polyacrylate (PAALi). The sintering temperature of LiFePO4/C precursor is studied by thermo-gravimetric (TG)/differential thermal analysis (DTA). The physical properties of LiFePO4/C are then investigated through analysis using by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and the electrochemical properties are investigated by electrochemical impedance spectra (EIS), cyclic voltammogram (CV) and constant current charge/discharge test. The LiFePO4/C composite with the particle size of ∼200 nm shows better discharge capacity (156.4 mAh g−1) than bare LiFePO4 (52.3 mAh g−1) at 0.2 C due to the improved electronic conductivity which is demonstrated by EIS. The as-prepared LiFePO4/C through this method also shows excellent high-rate characteristic and cycle performance. The initial discharge capacity of the sample is 120.5 mAh g−1 and the capacity retention rate is 100.6% after 50 cycles at 5 C rate. The results prove that the using of organic lithium salts can obtain a high performance LiFePO4/C composite.

Research highlights
► LiFePO4 can be synthesized from Fe2O3 by a sequence of free-radical reactions.
► Organic lithium salts can avoid the composition segregation of the precursor.
► Low cost ferric oxide and environmentally friendly distilled water are used.