One-step microwave synthesis and characterization of carbon-modified nanocrystalline LiFePO4

Abstract The precursors of LiFePO 4 were prepared by a sol–gel method using lithium acetate dihydrate, ferrous sulfate, phosphoric acid, citric acid and polyethylene glycol as raw materials, and then the carbon-modified nanocrystalline LiFePO 4 (LiFePO 4 /C) cathode material was synthesized by a one-step microwave method with the domestic microwave oven. The effect of microwave time and carbon content on the performance of the resulting LiFePO 4 /C material was investigated. Structural characterization by X-ray diffraction and scanning electron microscopy proved that the olivine phase LiFePO 4 was synthesized and the grain size of the samples was several hundred nanometers. Under the optimal conditions of microwave time and carbon content, the charge–discharge performance indicated that the nanosized LiFePO 4 /C had a high electrochemical capacity at 0.2 C (152 mAh g −1 ) and improved capacity retention; the exchange current density was 1.6977 mA cm −2 . Furthermore, the rate capability was improved effectively after LiFePO 4 was modified with carbon, with 59 mAh g −1 being obtained at 20 C.