Reactive Deposition of Ultrathin Conformal Vanadium Pentoxide within Carbon Nanotube Buckypaper in Supercritical Fluid CO2 for Electrochemical Capacitor

Vanadium oxide carbon nanotubes sheets (buckypaper) composite electrodes were fabricated by supercritical fluid deposition to produce high performance, binder-free electrochemical capacitor electrodes. The precursor vanadium acetylacetonate (V­(acac)3) was deposited using carbon dioxide within the buckypaper followed by in situ oxidation by oxygen. The deposition process, and the morphology, structure and electrochemical properties of the composite electrodes, were analyzed in detail. Continuous ultrathin layers of V2O5 (up to ∼1 nm) of high conformity were deposited on the carbon nanotubes and uniformly distributed throughout the buckypaper, which was up to ∼200 μm thick. Compared to deposition by physical adsorption, substantially higher loading of the vanadium oxide was achieved, which resulted in excellent electrode performance. For example, a composite with 50 wt % of V2O5 was achieved, which had a total capacitance of 187 F/g in KCl aqueous electrolyte.