Amorphous titanium-oxide supercapacitors with high capacitance

An amorphous titanium-oxide film oxidized anodically on amorphous Ti-10at%V-15at%Si alloy ribbons demonstrated excellent electric properties. Specifically, it showed a remarkable increase in parallel capacitance Cp, series capacitance Cs, time constant RCs, and decrease in the dielectric loss with decreasing frequency. The oblate semicircle after a semicircle with a Warburg region in the Nyquist diagram and rapid increases in the real impedance in the low-frequency region in the Bode diagram demonstrated a parallel circuit comprising an electric transport resistance Re (0.64 MΩ), and a high electric double-layer capacitance C _dl (604.0 μF/cm ²) at a nanometer-sized (∼53 nm in convex size) uneven surface between an upper (Ti_0.84V_0.11Si_0.05)O_1.655 layer approximately 45-nm deep and air. The superior capacitances could be elucidated by electrostatic induction of a large positive charge to the uneven oxide surface based on the electronic conduction state derived from TiO₂/VO₂ nanostructural interfaces in the upper oxide layer.