Structure engineering in hexagonal tungsten trioxide/oriented titanium dioxide nanorods arrays with high performances for multi-color electrochromic energy storage device applications

Abstract A novel porous structure of hexagonal WO3/oriented TiO2 nanorods arrays (h-WO3/TiO2 NRAs) hybrid film was successfully prepared by a facile hydrothermal method. Benefiting from elaborately structure engineering, the hybrid film exhibited large transmittance modulation (ΔT633nm = 73.45%), high coloration efficiency (69.2 cm2·C-1), fast Li+ ions insertion kinetics (6.6 s/2.0 s for tc/tb), stable cyclic stability (maintains 92.9% of initial ΔT after 2000 cycles) as well as areal specific capacitance of 10.93 mF·cm−2 at the current density of 0.1 mA·cm−2. An electrochromic energy storage device (EESD) with six multi-color modulation modes (light gray, dark olive green, yellow green, lime green, dark green and dark blue) was successfully assembled by h-WO3/TiO2 NRAs hybrid film and electrodeposited-V2O5 film. Based on the excellent electrochromic and pseudocapacitive properties, the EESD promised a smart visual monitoring of the energy storage level and can light up a LED after charging, indicating a good energy storage application prospect.