Lithium-titanate-nanotube-supported WO3 for enhancing transmittance contrast in electrochromics

Abstract

Lithium titanate nanotubes (Li-TNTs) have been successfully synthesized. The inner and outer diameters of the nanotubes are 5 nm and 8 nm with an interlayer spacing of 0.83 nm. The nanotubes were in accordance with the Li1.81H0.19Ti2O5 · xH2O phase. The chemical component was Li0.9H1.1Ti2O5 · H2O as determined by ICP-AES. The Li-TNT-supported WO3 nanoparticle (WO3/Li-TNTs) thin film was prepared onto ITO glass via spin-coating and then fabricated with an electrochromic device. The Li ion diffusion coefficient in the WO3/Li-TNT film was 6.1 × 10−10 cm2 s−1, which is eight times higher than that for the pure WO3 film. The transmittance contrast of the pure WO3-based ECD was 53.3% at 600 nm. However, this increased to 74.1% for the WO3/Li-TNT-based ECD. Meanwhile, the color-switching times of the WO3/Li-TNT-based ECD were apparently shorter than the ones for the WO3-based ECD.