From Amorphous Macroporous Film to 3D Crystalline Nanorod Architecture: A New Approach to Obtain High-Performance V2O5 Electrochromism

A 3D crystalline V2O5 nanorod architecture on indium tin oxide substrates is prepared by simple annealing treatment of a colloidal crystal-assisted electrodeposited amorphous three-dimensionally ordered macroporous film at a low temperature of 350 degrees C. The crystalline nanorods exhibit a low length/diameter ratio with the typical width range of 80-180 nm, length range of 190-500 nm, and thickness of 30-50 nm. Colloidal sphere-assisted heterogeneous nucleation during electrodeposition and the anisotropic bonding of the V2O5-layered structure are two important factors for the morphological changes. Because of the large surface area, short lithium ion diffusion distance, and good electrolyte penetration, the 3D crystalline V2O5 nanorod architecture exhibits a highly reversible Li-ion insertion/extraction process (columbic efficiency up to 96.9%) with a five-color-change electrochromic performance, good transmittance modulation, and acceptable response times (8.8 s for coloration and 9.3 s for bleaching), making it a promising film electrode for electrochromic devices.