Synthesis, Structure And Properties Of PANI-V₂O₅ Electrochromic Nanocomposite Films

The synthesis, structure, properties and interface behavior of nanocomposite materials based on layered V2O5 and MoO3, which can be topotactically reacted with alkali-metal ions ( Li+, Na+, etc. ) have attracted more attention in recent years. The intercalation of polymer into the interlayer is expected to improve the interface and interlayer structure of these materials, resulting in desirable novel characteristics. In this dissertation, vanadium pentoxide sols were synthesized by melt quenching. Polyaniline/V2O5 nanocomposites were fabricated by V2O5 sol and aniline (Ani) with in situ oxidative polymerization, as followed the nanocomposite films were prepared with electrophoresis deposition (EDP). Meantime, the structure and properties of the films were investigated by XRD, FTIR, TG/DSC, SEM, etc.V2O5 thin films were successfully prepared on ITO substrate with cathode electrophoresis deposition (CED) through V2O5 sol. It is found that V2O5 thin films deposited by CED are a compact microstructure with finer adhesive force with ITO substrate and the thickness is uniform and controlled. Moreover, the films have an excellent cycle for lithium intercalation/deintercalation and good cycle stability.For PANI/V2O5 nanocomposite, owing to the presence of PANI in its emeraldine salt form, V2O5 act as a counterion to compensate the positive charge present on the nitrogen atom, so the nanocomposite suspension is formed by negatively charged ribbons. Therefore, the nanocomposite film is prepared with anode electrophoresis deposition (AED). Moreover, V2O5 is semiconductor and when PANI intercalated in the interlayer of V2O5, PANI enhances the conductivity of nanocomposite, which increases the electrophoresis velocity of sol particles.The results of XRD, TG/DSC and NMR show that the (001) crystal plane distance of (PANI)xV2O5 nH2O nanocomposite films(the molar ratio ofAni :V2O5=0, 0.25, 0.6, 1) increases from 1.129nm at 0 to 1.355nm at 1 after heat treatment. PANI can be completely intercalated into the interlayer of V2O5 xerogel at 0.5-0.6, whereas partial PANI can not be intercalated into V2O5 xerogel interlayer and exists outside of V2O5 xerogel interlayer at 1. The SEM micrographs of the films show that the surface of the nanocomposite film is highly textured, while V2O5 film is flat and featureless.The FT-IR, Raman and NMR analysis indicate that all vibrational modes change remarkably after PANI was intercalated into V2O5 xerogel interlayer, which shows that V-O-V band is involved in the redox reaction. The stretching vibration of V=O shifts to lower wavenumbers, which can be explained by a banding interaction between PANI and the V2O5 framework, most likely via NH-O=V bondsThe intercalation of PANI effectively shields the electrostatic interaction between Li+ ions and V2O5 layers, resulting in the improvement of the cycling reversibility and stability of Li+ ions insertion/extraction in the interlayer of V2O5 xerogel and the improvement of electrochromic behavior of the films. The electrochromic theory is discussed. The main problems were analyzed and the suggestions for the next research about the relative materials were proposed.