Study On Modification Of Lithium Iron Phosphate Cathode Material

Due to its low cost, good safety and cycling performance, thermal stability, free-pollution, thermally stable, smooth charge and discharge platform, the olivine structure of lithium iron phosphate (LiFePO4) as a kind of cathode materials in lithium-ion battery obtained extensive attentions. However, its mass application in industry has been limited by its low electronic conductivity and ionic conductivity, bad consistency and low tap density.In our study, the LiFePO4/C was synthesized by high temperature solid-state reaction method with dry ball-milling, Li2CO3, FeC2O4·2H2O and (NH4)HPO4were used as raw materials. By changing the synthesis conditions including ball-milling time, calcine time and calcine temperature, the best synthesis condition has been found. Glucose and citric acid were choosed as carbon sources. The characteristics and morphologies of the composites were investigated by XRD, SEM, TEM, Grading analysis, Four-point probe instrument, Raman spectrum analysis.The electrochemical performances LiFePO4/C were evaluated by battery testing system. The experiment results showed that the best synthesis condition is:dry ball-milling2houres and calcine10hours with the temperature of750℃.In this way, the discharge capcity of0.2C is131.4mAh/g. Different carbon sources brought difterent results. When the ratio of glucose and citric acid was1and carbon content was3.08%, the carbon layer’s degree of graphitization is the highest. The discharge capacity of LiFePO4/C composite material was158.2mAh/g at the rate of0.2C.