Synthesis of LiFePO4/C Composites Using Fe2P2O7 as Precursor by a Two-Setp Solid-State Method

Fe2P2O7 was prepared from Fe-P waste slag and CO2 using a solid-state method, and it was furtherly used as precursor of LiFePO4. The compositions and microstructures of the as-synthesized Fe2P2O7 and LiFePO4 were characterized by TG/DSC, XRD and SEM. It is found that Fe1.5P can be oxidized to Fe2P2O7 over 700 degrees C in CO2 atmosphere. The optimized synthesis of Fe2P2O7 is described as: mixture of Fe1.5P and H3PO4 (extra P source) is calcined at 800 degrees C for 6 h, which gives the highest specific capacity of LiFePO4. The discharge capacity of the as-synthesized LiFePO4 can reach as high as 130, 126, 117, and 108 mAh center dot g(-1) with C-rates of 0.1C, 0.2C, 0.5C and 1C, respectively.