Synthesis And Properties Of Vanadium Penoxide/Grapnene Nanocomoosite Films

Electrochromic materials show potential applications in numerous fields, such as energy efficient smart windows, non-radiative displays and automatically dimming rearview mirrors. With the increase of energy consumption and the development of science, electrochromic materials have drawn more and more attention and will become even more important in the future. V2O5nanofilms have drawn great attention because of the multi-electrochromic behavior and high reversibility. However the moderate electrical conductivity of V2O5xerogel needs to be improved in order to be used in electrochromic devices effectively. The discovery of graphene with fast electron transportation property provides a new way to improve the response rate of V2O5xerogel. In this dissertation, we have synthesized V2O5graphene nanocomposite films by sol-gel method. It is expected that the unique nanocomposite films can be formed through synergistic effect of the two components. The structure, electrochemical property and electrochromic property of the films were characterized. The optimum content of graphene was determined and its action mechanism was discussed. This dissertation mainly include the following conclusions:V2O5/graphene nanocomposite films are layered structure with V2O5matrix structure. The inserted graphene expanded the interlayer distance which was in favor of the intercalation of Li+. FESEM images showed that the nanocomposite films were smooth, and the thickness was about300nm. As electrochromic material, the V2O5/graphene nanocomposite films showed transmissive color change of yellow-green-blue in the electrochromic process. We analyzed CV curve, capacity charge and the response rate of nanocomposite films with different content of graphene, and found that the content is the major factor that affects the performance of nanocomposite films, and the optimum content of graphene was4.0wt%. The nanocomposite films present improved cycle stability and reversibility. After50cycles, the Li+intercalation/deintercalation reversibility of V2O5/graphene nanocomposite films was95.8%, and the charge retention rate was86.3%. The response time of V2O5graphene nanocomposite films is less than that of V2O5xerogel films. This is due to improved conductivity of nanocomposite films. One of the most important characteristics of electrochromic materials is the optical modulatory range. The UV-vis transmittance spectra showed that the addition of graphene enlarged the optical modulatory range of V2O5xerogel films. The optical modulatory range of V2O5/graphene nanocomposite films was1.5times larger than V2O5xerogel films. The V2O5/graphene nanocomposite films are suitable for fast switching electrochromic devices.