LiFePO₄ Cathode Nanocomposite with PPy/PEG Conductive Network

Abstract

The polypyrrole-LiFePO4 composites were synthesized by simple chemical oxidative polymerization of pyrrole (Py) monomer directly on the surface of LiFePO4 particles. Properties of resulting polypyrrole-LiFePO4 (PPy-LiFePO4) samples (especially conductivity) are strongly affected by the preparation technique, polymer additives and conditions during synthesis. The polyethylene glycol (PEG) as additive during polymerization was used to increase the PPy-LiFePO4 conductivity. The electrochemical behaviour of samples was examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and the chemical stability was evaluated using X-ray photoelectron spectrometry (XPS). It was found that PPy-PEG composite polymer decrease particle to particle contact resistance. Impedance measurements showed that the coating of PPy-PEG significantly decreases the charge transfer resistance of LiFePO4 electrodes. Addition of polyethylene glycol (PEG) during PPy polymerisation leads to enhanced electronic conductivities.