Analysis of structural morphological changes from 3DOM V2O5 film to V2O5 nanorods film and its application in electrochromic device

Abstract

Nanoscale V 2 O 5 films possess excellent electrochemical properties and have great potential for application in electrochromic devices. Herein, we report a novel strategy for the transformation of three-dimensionally ordered macroporous(3DOM) V 2 O 5 films into V 2 O 5 nanorods film using a simple low-temperature annealing treatment, in which the heterogeneous nucleation sites provided by PS colloidal sphere surface, the anisotropic bonding of V 2 O 5 , atomic rearrangement, and Ostwald ripening are all important factors affecting the morphological transformation. According to this study, during the preparation of 3DOM V 2 O 5 films, a small number of oxygen vacancies were introduced into the V 2 O 5 lattice, and the annealing treatment (250–400 °C, 4–8 h) controlled the concentration of oxygen vacancies. Compared with the ion storage capacity of V 2 O 5 films prepared by conventional sol-gel dip-coating method (17.79 mC cm −2 for unannealed V 2 O 5 films and 13.90 mC cm −2 for V 2 O 5 films after 6 h of annealing at 350 °C), the 350°C-6h films with nanorod structure had the highest ion-storage performance, the initial value raised to 98.77 mC cm −2 . Further, the cycling stability was excellent, with only a 6.1% decrease after 5000 cycles. This was because of the special nanorod structure and the presence of a certain number of gradient oxygen vacancies in the 350°C-6h film. The 350°C-6h film also had good electrochromic properties, a wide range of transmittance modulation (73.6%), and a fast response time (3.2 s for coloring and 3.9 s for bleaching). In addition, electrochromic devices (ECDs) with 350°C-6h films as both ion-storage layers and electrochromic layers have been successfully assembled, which exhibit high performance. • 3DOM V 2 O 5 film was prepared on ITO substrate by Template assistance sol-gel method. • Annealing induced morphology change from 3DOM to nanorods in V 2 O 5 films. • The annealing affects oxygen vacancy concentration, and in turn affects on ion storage capacity. • V 2 O 5 nanorodsfilms presents excellent capacity and cycle performance for lithium storage. • The electrochromic device assembled with V 2 O 5 film showed fascinating performance.