Characterization of Li–V–O nanorod phases and their effect on electrochemical properties of Li1+xV3O8 cathode materials synthesized by hydrothermal reaction and subsequent heat treatment

Lithium vanadium oxide (Li1+xV3O8, x = 0.2) cathode materials were synthesized via a simple hydrothermal reaction followed by heat treatment at elevated temperatures, and the electrochemical performance of as-synthesized LiV3O8 as a cathode material for lithium ion batteries was investigated using galvanostatic discharge–charge cycling and electrochemical impedance spectroscopy. It reveals that different thermal treatment histories resulted in drastic changes in sizes/morphologies and electrochemical properties. The samples that were heat treated at 300 °C contained many nanorod-like particles, particularly at the surface of agglomerated LiV3O8 particles. Such nanorod-shaped Li–V–O compounds exhibit two different crystal structures: either a defective LiV3O8 or a Li0.3V2O5 structure. In addition, the nanorod-shaped Li–V–O compounds in the galvanostatically cycled samples could not be observed using high-resolution scanning electron microscopy (HRSEM) because of their structural instability, which can be attributed to the deterioration of their electrochemical properties during cycling. In contrast, the samples treated at 400 and 500 °C exhibited a bi-modal particle distribution and estimated sheet-like morphologies with no impurities, respectively. They also indicated excellent electrochemical properties.

► LiV3O8 were synthesized via a hydrothermal reaction followed by heat treatment. ► The electrochemical performance of as-synthesized LiV3O8 was investigated. ► Nanorod-shaped Li–V–O either a LiV3O8 or a Li0.3V2O5 structure were observed. ► Such nanorod phases are structurally defective or instable against cycling. ► The reason for the drastic capacity fading was discussed using HRTEM, HRSEM and EIS.