Synthesis And Electrochemical Property Of LiFePO₄/C For Lithium-Ion Battery Cathode Material

The LiFePO4is a kind of extremely potential battery materials because of its high capacity, excellent cycle stability, better thermal stability and less pollution. However, the major obstacle in practical used is in its low electronic conductivity, low ionic diffusion and high cost. In order to reduce the cost and improve the electrochemical properties of LiFePO4, the samples are synthesized by carbothermal reduction method using cheap Fe3+compounds as iron precursors. The microstructure and electrochemical properties of the LiFePO4have been characterized by XRD, SEM and galvanostatic charge-discharge methodes. The main experimental results are listed as follows:(1) The LiFePO4samples are successfully synthesized by carbothermal reduction method using cheap FePO4, Fe2O3, Fe2(SO4)3as iron precursors. The XRD results show that the LiFePO4phase can be found in the samples by using different Fe3+compounds as iron precursors. The SEM photographs of the samples indicate that the grain size of the material synthesized with FePO4as iron precursors is relative small, and the electrochemical property of this sample is quite good. The initial discharge capacity of the material prepared by using FePO4as iron precursor is124.3mAh/g, and its value reaches143.5mAh/g after100charge-discharge cycles, that is, the discharge capacity increased by15.4%after100charge-discharge cycles.(2) The influence of different ways of carbon coating on the microstructure and electrochemical properties of the materials has been studied. The SEM photographs of the samples indicate that the grain size of the material prepared by bi-carbon-coated is smaller than that of the material prepared by uni-carbon-coated. The electrochemical property of the former is better than that of the latter. As the content of C6H12O6in the material prepared by bi-carbon-coated being higher than15%, the electrochemical property of this sample is the most optimized improvement. The initial discharge capacity of this sample is145.2mAh/g, and its value reaches160.1mAh/g after100charge-discharge cycles, that is, the discharge capacity increased by10.3%after100charge-discharge cycles.(3) The experimental results obtained in present work indicate that for the samples prepared by using different Fe3+compounds as iron precursors, the discharge capacity of the material increase with the number of charge-discharge cycles as the charge-discharge cycles less than100.