Structural and electrochemical studies of PPy/PEG-LiFePO4 cathode material for Li-ion batteries

A simple chemical oxidative polymerization of pyrrole (Py) directly onto the surface of LiFePO4 particles was applied to the synthesis of polypyrrole-LiFePO4 (PPy-LiFePO4) powder. The LiFePO4 sample without carbon coating was synthesized by a solvothermal method. The polyethylene glycol (PEG) was used as additive during Py polymerization for increasing the PPy-LiFePO4 conductivity. Properties of resulting LiFePO4, PPy-LiFePO4 and PPy/PEG-LiFePO4 samples were characterized by XRD, SEM, TGA and galvanostatic charge–discharge measurements. These methods confirmed the presence of polypyrrole on LiFePO4 particles and its homogeneous distribution in the resulting powder material. The PPy/PEG-LiFePO4 composites show higher discharge capacity than pure LiFePO4, as PPy/PEG network improves the electron conductivity. It presents specific discharge capacity of 153 mAh/g at C/5 rate.