Carbothermal reduction preparation and performance of LiFePO4/C by using ammonium jarosite extracted from vanadium slag as iron source

LiFePO4/C cathode materials are synthesized by carbothermal reduction process using ammonium jarosite as iron source and rock sugar as carbon source. The ammonium jarosite is synthesized from the iron-rich lixivium which is obtained from the extracted vanadium residue by ammonium sulfate roasting and deionized water leaching. The effects of different molar ratios of C to LiFePO4 on the performance of the as-synthesized LiFePO4/C have been scrutinized using charge–discharge cycling and electrochemical impedance spectroscopy (EIS). The result shows that the LiFePO4/C sample with a molar ratio of C to LiFePO4 of 1.2 prepared from ammonium jarosite exhibits an initial discharge capacity of 163.8 mAh g−1 at the current density of 0.1 C, which is about 96% of the theoretical capacity, and the highest average discharge specific capacity, which is 162.3, 154.9, and 120.9 mAh g−1 at the current density of 0.05, 0.1, and 1 C, respectively. EIS results reveal that the cathode exhibits the lowest charge transfer resistance at 200.8 Ω with a molar ratio of C to LiFePO4 of 1.2. This work proposes a novel and effective method to utilize the industrial waste residue.