PANI-PEG copolymer modified LiFePO4 as a cathode material for high-performance lithium ion batteries

The poor electronic conductivity and low lithium ion diffusion rate of a LiFePO4 cathode material are the two major obstacles for its commercial applications in the power lithium ion batteries. This article utilized an electroactive and ion conductive copolymer, polyaniline-poly(ethylene glycol) (PANI-PEG), to modify carbon-LiFePO4 (cLFP) by a facile in situ chemical copolymerization method. The structure and morphology of the cLFP/PANI-PEG composite were confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compared with a cLFP/PANI composite, the cLFP/PANI-PEG composite exhibited a more uniform and full polymer coating layer. Furthermore, this cLFP/PANI-PEG cathode material exhibits excellent cyclic stability (95.7% capacity retention after 100 cycles at 0.1 C) and high rate capability (125.3 mA h g(-1) at 5 C) as the PANI-PEG copolymer coating layer facilitated electron and ion transport within the electrode. Electrochemical impedance spectroscopy (EIS) proved that the lithium ion diffusion in the cLFP/PANI-PEG composite was increased significantly by one order of magnitude compared with cLFP, indicating its possibility to be served as a cathode material for high-performance lithium ion batteries.