A Novel Strategy for the Synthesis of Fe3(PO4)2 Using Fe–P Waste Slag and CO2 Followed by Its Use as the Precursor for LiFePO4 Preparation

A novel method whose starting materials was Fe–P waste slag and CO2 using a closed-loop carbon and energy cycle to synthesize LiFePO4/C materials was proposed recently. In the first step, Fe–P slag was calcinated in a CO2 atmosphere to manufacture Fe3(PO4)2, in which the solid products were tested by XRD (X-ray diffraction) analysis and the gaseous products were analyzed by the gas detection method. In the second step, as-synthesized Fe3(PO4)2 was further used as the Fe and P source to manufacture LiFePO4/C materials. Also, the influence of the preparation conditions of Fe3(PO4)2, including calcination time and calcination temperature, on the energy storage properties of as-obtained LiFePO4/C was investigated. It was found that the LiFePO4/C materials, which was synthesized from Fe3(PO4)2 obtained by calcining Fe–P waste slag at 800 °C for 10 h in CO2, exhibited a higher capacity, better reversibility, and lower polarization than other samples. The discharge capacity of as-obtained LiFePO4/C can reach 145 mAh/g at 0.1 C current rate. This work puts forward an environment-friendly method of manufacturing LiFePO4/C cathode materials, which has a closed-loop carbon and energy cycle.