Synthesis and electrochemical properties of InVO ₄ nanotube arrays

This paper reports an experimental study on the synthesis and electrochemical properties of InVO4 nanotube arrays fabricated by capillary-enforced sol-filling in templates in combination with solvent-evaporation induced deposition. InVO4 sol was synthesized using the sol–gel route from vanadium oxoisopropoxide and indium nitrate with ethanol as the solvent. Nanotube arrays of InVO4 were prepared by filling the sol into pores of polycarbonate membranes and pyrolyzing through sintering. Another type of InVO4 nanotube array (InVO4–acac) was obtained from the sol with the addition of acetyl acetone (acac). For comparison purposes, InVO4 films were prepared by drop casting from the same InVO4 sol. Films and the two types of nanotube array of InVO4 annealed at 500 °C consisted of mixed monoclinic (InVO4-I) and orthorhombic (InVO4-III) phases. Scanning electron microscopy (SEM) characterization indicated that the nanotubes were aligned perpendicular to the substrate surface with an outer diameter of ∼200 nm for short InVO4 nanotubes and ∼170 nm for long InVO4–acac nanotubes. Chronopotentiometry results revealed that the InVO4–acac nanotube array has the highest charge capacity (790 mAh g−1), followed by the InVO4 nanotube array (600 mAh g−1) then the InVO4 film (290 mAh g−1). Such enhanced lithium-ion intercalation properties were ascribed to the large surface area and short diffusion distance offered by nanostructures and amorphisation caused by acetyl acetone in the case of InVO4–acac nanotube arrays.