Cobalt-doped V2O5 nanowire arrays on Ti foil for enhanced lithium-ion storage

Cobalt (Co)-doped V2O5 nanowire arrays are prepared using a simple hydrothermal method by controlling appropriate molar ratios of cobaltous acetate (Co(CH3COO)2·4H2O) and ammonium vanadate (NH4VO3). The products are characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Fourier-transform infrared spectroscopy. The nanowires are identified as cobalt-doped V2O5 when the molar ratio of cobalt/vanadium precursors is less than 0.064 (calculated from raw materials); while as the molar ratio increases to 0.128, the nanowires are composed of a mixture of V2O5 and Co3O4. The valence states of Co, O and V are tested by X-ray photoelectron spectroscopy, and the distribution of these elements is confirmed by elemental mapping. The prepared samples are studied and compared with their lithium-storage properties using cyclic voltammetry, charge-discharge test and rate performances. The Co-doped V2O5 nanowires have a higher electrochemical lithium-storage capacity than that of the mixed V2O5/Co3O4 nanowires. At a current density of 30 mA g−1, an initial discharge capacity of 624.64 mAh g−1 is achieved in a voltage range of 2-4 V.