Effect of consumption amount of lithium salt on the properties of LiFePO4/C cathode materials

LiFePO4/C composites were synthesized by carbothermal reduction method and the effect of consumption amount of lithium salt on the properties of LiFePO4/C materials was systematically investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), carbon/sulfur determinator and constant-current charge/discharge test. The results showed that the lithium salt addition should exceed the theoretical value in order to make up for the lithium ion loss during the synthesis and SEI film formation process and the resulting carbon contents in these samples were all about 2.3 wt%. The optimal addition of lithium salt was 8% excess of the theoretical value. Electrochemical results showed that the optimal sample exhibited high discharge capacities of 157.6 and 143.5 mAh/g at 0.2C and 1C rates, respectively. The capacity was reduced to 128.8 mAh/g after 100 cycles at 2C rate, with a cycling capacity retention rate of 99.8%.