Electrochemical Performance of 0.7LiFePO4•0.3Li3V2(PO4)3/C Cathode Materials Using Polyethylene Glycol as Carbon Source

Different molecular weight of polyethylene glycol (PEG), including PEG-200, PEG-600, PEG-1000, PEG-2000 and PEG-6000, were used as carbon sources and reduction agents for preparation of 0.7LiFePO(4)center dot 0.3Li(3)V(2)(PO4)(3)/C composites via spay-drying followed solid-state reaction approach. The structure and morphology of the 0.7LiFePO(4)center dot 0.3Li(3)V(2)(PO4)(3)/C composite samples were characterized by X-ray diffraction(XRD), Raman spectroscope and field-emission scanning electron microscope (FE-SEM). The diffraction peaks of the synthesized compound were composed of both orthorhombic LiFePO4 and monoclinic Li3V2(PO4)(3), indicating the synthesized compound is a mixture phase of LiFePat and Li3V2(PO4)(3). The structure of residual carbon was characterized by Raman spectroscope. A lower intensity ratio of the I-D/I-G band for PEG-200 in Raman spectrum indicated more graphite clusters in the structure of carbon, which would enhance the electronic conductivity of the residual carbon. The composites showed higher discharge capacity, better rate capability and cyclic performance. Even at a high charge-discharge rate of 10C, it still maintained a discharge capacity of 120 mAh/g in the potential range of 2.0-4.3 V.