Polycrystalline vanadium oxide nanorods: growth, structure and improved electrochemical response as a Li-Ion battery cathode material

Abstract

Thermally removing amine molecules that serve as chemical templates for vanadium oxide nanotubes is demonstrated to significantly improve the performance when tested as a cathode material in Li-ion battery cells. Capacity fading issues associated with blocked intercalation sites on the (010) faces of layered vanadium oxide that form the nanotubes are prevented. Thermal treatment of the nanotubes up to 600°C is shown to cause a specific conversion from nanotubes to polycrystalline nanorods and removal of the organic template. The conversion process was monitored by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy and infra-red spectroscopy. In a potential window of 4.0–1.2 V drawing 30 μA (C/30), the nanorods show improved specific capacities of ∼280 mAh g−1 with a modest 6% capacity fade compared to ∼8 mAh g−1 with 62% capacity fade for the VONTs. The improvements in specific capacity and cycling performance are due to the successful removal of amine molecules and conversion to nanorods containing nanoscale crystals. The cathode material also demonstrated enhanced energy densities (∼700 W h kg−1) compared to composites of the same overall weight, without conductive carbon additives or polymeric binders.