The Performance Of Conductive Polymer As Carbon Source Coated LiFePO₄ Research

Olivine-type LiFePO₄ is a kind of excellent cathode material for lithium ion battery,which has many advantages such as rich in raw material source,high theoretical specific capacity,environment-friendly,high safety and high cycle stability.However,due to the low diffusion rate of Li+ and the low electronic conductivity of pure LiFePO₄,the electrochemical properties are affected.Therefore,it is necessary to modify the LiFePO₄ to enhance its electrochemical properties.In this paper,the high temperature solid state synthesis method was used to prepare LiFePO₄/C_PANI-Cl composite with uniform carbon coating on the surface of LiFePO₄ by using conductive polymer PANI-Cl as carbon source.The microstructure and morphology of products were analyzed By XRD,TEM,SEM and FTIR.The effects of different PANI-Cl contents and sintering temperature on the properties of LiFePO₄/C_PANI-Cl composites were investigated.It was found that the particle size distribution of LiFePO₄/C_PANI-Cl composite prepared by using 10 wt.%PANI-Cl as the carbon source and sintering temperature of 700 ? is uniform.The initial discharge specific capacity at 0.2C rate is 163 mAh × g-1,and the specific discharge capacity at 10 C rate is 106 mAh×g-1,which is higher than 61 mAh×g-1and 148 m Ah × g-1 of LiFePO₄/C composites prepared by the sucrose as carbon source,respectively.After 100 cycles,the specific discharge capacity of LiFePO₄/C_PANI-Cl composites is only loss 2%,which is much better than that of LiFePO₄/C composite's 5%under the same conditions.In addition,the LiFePO₄/C_PANI were prepared by in-situ polymerization and sintering method using PANI and sucrose as mixed carbon sources.The experimental lithium ion battery prepared with LiFePO₄/C_PANI composite as cathode material has good high rate performance and cycle performance.The initial discharge specific capacity reaches 160.4mAh×g-1 at 0.2C rate,and maintain 136.8 mAh×g-1 at 5C rate,still 94.5 mAh×g-1 at 60 C.