Characteristics of xLiFePO4·y Li3V2(PO4)3 electrodes for lithium batteries

A series of mechanical mixture of lithium–iron–vanadium–phosphate compositions that can be represented in two-component notation, xLiFePO4·y Li3V2(PO4)3 (LFVP), has been evaluated as electrodes in lithium cells for x:y = 0:1, 1:1, 5:1, 10:1, and 1:0, in which an olivine component, LiFePO4 (LFP), and a monoclinic component, Li3V2(PO4)3 (LVP), coexisted. Powder X-ray diffraction (XRD) patterns show that the end members and the electrochemical profiles of cells with these electrodes are consistent with those expected for the olivine LiFePO4(x = 1, y = 0) and for monoclinic Li3V2(PO4)3 (x = 0, y = 1). XRD data and the changes of cell parameters indicate that there existed some V- and Fe-doping in the composite xLiFePO4·y Li3V2(PO4)3, resulting with a good performance compared with single LiFePO4 and Li3V2(PO4)3. Electrochemical characteristics were evaluated by using cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the electron transfer activity and the lithium ion diffusion rate in LFVP are better than single LFP and LVP.