Polyol Synthesis of Ti-V₂O₅ Nanoparticles and Their Use as Electrochromic Films

Herein, the successful synthesis of Ti-doped vanadium pentoxide from a polyol process is reported. A high Ti concentration (up to 8.5 mol % of the total metallic content) can be inserted in vanadium oxide thanks to the synthesis route leading to nanometric crystallites. X-ray diffraction patterns were refined showing the insertion of the titanium ions inside the free pentacoordinated sites in opposition to the vanadium square pyramidal sites. This crystal organization was shown in good agreement with the ab initio positioning performed from valence calculation. The nanoparticles, NPs, of Ti-doped V₂O₅ compounds were characterized as electrochromic materials. Films elaborated from a dip-coating process from oxide particle suspensions exhibited three distinct colorations during the redox cycling in lithium-based electrolyte. These colors were associated with three distinct oxidation states for the vanadium ions: +III (blue), +IV (green), and +V (orange). The morphology of the films was shown to drastically impact the electrochromic performances in terms of electrochemical capacity and stability.