Synthesis, Structure And Properties Of PEO-V₂O₅-MoO₃ Nanocomposite

The synthesis, structure, properties and interface behavior of nanocomposite materials based on layered MoO3 and V2O5 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, the (PEO)X V2O5-MoO3 nH2O (x=0, 0.5, 1, 2) nanocomposite films were prepared by polymer solution direct intercalation via sol-gel method. Meantime, the structure and properties of the films were investigated.The results of XRD, DTA-TG show that V2O5-MoO3 nH2O xerogel is a uniform single state, having a one-order layered structure which arranges in c-direction. The (001) crystal plane distance of (PEO)X V2O5-MoO3 nH2O (x=0, 0.5, 1, 2) nanocomposite films increases from 1.3171nm at x=0 to 1.8945nm at x=2 after heat-treatment. PEO can be completely intercalated into the interlayer of V2O5-MoO3 xerogel in form of amorphous state at x 1, whereas partial PEO can not be intercalated into V2O5-MoO3 xerogel interlayer and exists outside of V2O5-MoO3 xerogel interlayer in form of crystalline state at x=2. The SEM micrographs of xerogel thin films show that the surface of the films is homogeneous, no cracks and holes are observed and it has a fiber-like microstructure.The IR analyses indicate that all vibrational modes change remarkably after PEO was intercalated into V2O5-MoO3xerogel interlayer. The stretching vibration of V=O shifts to low mavenumber, which is contributed to the M=O-O bonding interaction which is similar with H-bonding but stronger than H-bonding between PEO and V2O5-MoO3 layers.The XPS analyses show that there were two different chemical conditions of Li+ ions when Li+ ions were inserted into V2O5-MoO3 xerogel, corresponding to the Li+ ions in the interlayer and interstitial positions ( localized by the layers ) of V2O5-MoO3 lattice, respectively. After the intercalation of PEO, the content of Li+ ions in the interlayer was greatly increased and the interaction between Li+ ions and their environments was decreased.The increase of electrical conductivity of V2O5-MoO3 nanocomposite films to V2O5 films results from the substitution of Mo for V, which leads to the increase of V4+ ion content. The PEO-V2O5-MoO3 xerogel thin films show the excellent cycling reversibility and stability of Li+ ions insertion/extraction in the interlayer of V2O5-MoO3 xerogel. The intercalation of PEO leads to the structural rearrangement, resulting in the improvement of the Li+ ions content in the films. Moreover, the intercalation of PEO enhances the electrochromic efficiency, resulting in the improvement of electrochromic behavior of the films.This work was supported by the National Natural Science Foundation of China (Grant No. 59802009 and No. 50172036) and the Natural Science Foundation of Hubei Province.