Effects of Ni doping on the initial electrochemical performance of vanadium oxide nanotubes for Na-ion batteries.

In this study, we demonstrated the intercalation of Na in hydrothermally synthesized VOx nanotubes (NTs) and Ni-doped VOx NTs. The changes induced in the structures of the two nanomaterials during the Na intercalation process were investigated through X-ray diffraction (XRD) analyses. It was observed that the initial capacity and rate performance of the Ni-doped VOx NTs were improved. The results of X-ray photoelectron spectroscopy (XPS) and conductance measurement confirmed that higher initial capacity and rate performance were attributed to an increase in the valence states of vanadium and increased conductivity after the Ni exchange process.