Preparation of high performance LiFePO4/C by extracting iron element from iron tailings by concentrated sulfuric acid hot dip method

Abstract

LiFePO4/C cathode materials are synthesized by carbothermal reduction process using FePO4 as iron and phosphorus source, and starch as carbon source. The FePO4 precursor was prepared by leaching iron tailings with concentrated sulfuric acid and then leaching with phosphoric acid and hydrogen peroxide. The morphology and structure of FePO4 precursors prepared under different pH conditions were studied by using thermogravimetric-differential analysis (TG-DTA), infrared analysis (FTIR), x-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The effect of the FePO4 material on the properties of the synthesized LiFePO4 cathode was investigated by charge and discharge cycles. On this basis, the effects of different molar ratios of C and LiFePO4 on the performance of synthetic product LiFePO4/C were studied using starch as carbon source. The results show that the FePO4 precursor prepared under the condition of pH 2 is the raw material, and the LiFePO4/C cathode material synthesized by adding 45% carbon has the best performance. The first cycle discharge capacity reached 142.6 mAh g−1 at a current density of 0.1 °C, reaching 83.9% of its theoretical capacity. This work proposes a novel and effective method to utilize the iron tailings.