Structural and electrochemical characterization of thermally treated vanadium oxide nanotubes for Li-ion batteries

Vanadium oxide nanotubes (VONTs) have been successfully synthesized by hydrothermal treatment of a mixture of vanadium oxide xerogel and nonylamine. Traditionally dodecylamine and hexadecylamine are used as the structure maintaining template. In this study, however, evidence of high quality nanotubes templated with nonylamine is presented. Thermogravimetric analysis was used to determine the temperature at which the amine molecules can be removed from the nanotubes. The removal of amines is desirable as heavy functionalization of VONTs by amine molecules can impede the intercalation of lithium ions. The removal of the amine chains resulted in a change in morphology from pristine nanotubes to polycrystalline vanadium oxide nanorods. High resolution transmission electron microscopy was used to characterize the VONTs before and after annealing to high temperatures. Fourier transform infrared spectroscopy confirmed the removal of the amine template after annealing. Galvanostatic discharge tests were performed to compare the electrochemical behavior of bulk V₂O₅ powder, VONTs and polycrystalline nanorods (poly-NRs). A comparison of their specific capacity values after the first discharge is also presented.