▎ 摘　　要

Vanadium oxides (VOx) have been extensively investigated over the past years as promising electrode materials for alkali ion batteries owing to their rich and interesting electrochemical properties. Further improvements on electrochemistry of VOx materials have been possible by working at the nanoscale as well as by realising hierarchical composites with various carbon allotropes. However, the nanocomposite synthesis methods are not always efficient, nor green, requiring either expensive precursors, extended synthesis time or harmful reagents. Herein, we report on rapid and environmentally friendly synthesis methods of a library of VOx@rGO composites via impregnation and hydrothermal protocols using a cheap and commercially available V2O5 precursor. Different oxidation states, crystalline phases and nanoscale morphologies can be reproducibly accessed and their physico-chemical properties have been characterized. The electrochemical properties (lithium and sodium ion storage) of the synthesized VOx@rGO nanocomposites and phases have been critically inter-compared between these but also with respect to commercial (CM) VOx-based electrodes. Whereas nanostructuring is found to impact the power-rate performances, the amount of stored charge and the cycling stability are sensitively dependent on the cycling potential window, while being minorly affected by the morphology and synthesis method. The composites are also found to exhibit different electrochemistry for sodium storage, with more sloping potential profiles. Peculiarly, the synthesized V2O3@rGO composite shows no signs of electrochemical activity pointing towards the electrochemical inertness of this particular V2O3 composite and phase. This work could serve as reference for future developments on this class of important battery materials as it is one of the few studies describing a comprehensive and comparative study of several different influential parameters on the electrochemical behaviour of vanadium oxides in different oxidation states, crystalline phases and morphologies.