Electrochromic and electrical properties of layered and tubular vanadium pentoxide thin films

Due to its lithium ion intercalation capability, vanadium pentoxide is extensively studied for applications such as electrode material for pseudocapacitors, electrochromic devices, and cathodes in high capacity lithium ion batteries. Vanadium oxide has a layered structure and, in order to enhance lithium ion intercalation, templating methods are proposed in this work to create porosity in the film. The aim of this work is to evaluate how the morphology of vanadium pentoxide thin films is instrumental in obtaining a material with a high lithium ion intercalation capacity. With an appropriate morphology, the performance of vanadium oxide as electrochromic material and as cathode in lithium ion batteries can be improved significantly. For this purpose, both layered (dense and porous) and nanorod films were prepared and characterized. Scanning electron microscopy, cyclic voltammetry and electrical impedance spectroscopy measurements were used for the characterization of the different V₂O₅ films. The results showed the very good electrochromic properties of the porous film built up with polystyrene microspheres and triblock copolymer as templating materials as well as of the nanorod films fabricated by thermal annealing.