Preparation and characterization of PPy/LiFePO₄ composite material as cathode

Polypyrrole was coated onto pure LiFePO₄ particles to form polypyrrole/lithium iron phosphate(PPy/LiFePO₄) composite material by chemical oxidative polymerization, with ferric trichloride(FeCl₃) as oxidant, benzene sulfonic acid sodium salt as dopant. The molecular structure and morphology of PPy/LiFePO₄ were characterized by FTIR, XRD and SEM. The electrochemical performances of composite were measured by electrochemical workstation and charge-discharge test system. It is found that the battery with PPy/LiFePO₄ composite as cathode shows better charge-discharge performance. The discharge capacity of PPy/LiFePO₄ composite is 163 mAh穏^-1, which is higher than that of LiFePO₄, when the mass fraction of PPy is 17.0% and the current is 0.1 mA.The discharge specific capacity of composite is still 94.9% of initial capacity after 50 cycles. Compared with pure LiFePO₄, the coating of proper amount of PPy can improve the electronic conductivity of LiFePO₄. As the effective utilization of LiFePO₄ increases, both the specific capacity and cycle performance of PPy/LiFePO₄ composite improves.