Improved electrochemical properties of (1-x) LiFePO4•xLi3V2(PO4)3/C composites prepared by a novel sol-gel method

In this study, (1 - x) LiFePO4 center dot xLi(3)V(2)(PO4)(3)/C (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1) composite cathode materials are synthesized using CH3COOLi center dot 2H(2)O, Fe(CH3COO)(2)center dot 4H(2)O, V2O5, and H3PO4 as starting materials with N, N-dimethyl formamide as a dispersing agent using a novel sol-gel method. The structure, morphology, and electrochemical properties of the composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge measurements. XRD patterns of the compound indicate the coexistence of LiFePO4 and Li3V2(PO4)(3). Compared to pristine LiFePO4 and Li3V2(PO4)(3), the composite materials exhibit smaller particle size, which can facilitate Li+ extraction and insertion, thereby leading to an improvement in the electrochemical properties. Among all the composites synthesized, 0.8LiFePO(4)center dot 0.2Li(3)V(2)(PO4)(3)/C exhibits the best electrochemical performance with an initial specific discharge capacity of 158.7 mA h g(-1) at 0.1C in the voltage range of 2.5-4.3 V. When the current rate is increased to 5C and 10C, the capacity of 0.8LiFePO(4)center dot 0.2Li(3)V(2)(PO4)(3)/C is retained at 125.8 and 110.8 mA h g(-1), respectively, indicating the cycling stability of the composite.