The Study On The Polyaniline/Vanadium Pentoxide Composite Electrode Material

V₂O₅ xerogel is a promising cathode material for use in Li-ion battery due to its high theoretical specific capacity and processability, however, poor electronic conductivity,low diffusion coefficients of Li+ and structural changes within the host matrix still remain as issues to be addressed. Hybridization of this oxide with electronically conducting polymer has been regarded as an interesting approach to overcoming these disadvantages. In this dissertation, the synthesis,structure and electrochemical behavior of a composite material, polyaniline/vanadium pentoxide (PAn/V₂O₅), were studied. We have investigated the influence of An/V₂O₅ molar ratio,reaction temperature and time of this hybrid in order to optimize its performance as electrode materials. PAn/V₂O₅ hybrid has been synthesized by the oxidation of aniline with V₂O₅ xerogel as oxidant. FT-IR spectra shows that the polyaniline is present primarily in the emeraldine salt form, and the polymeric chains interact with inorganic framework, most likely via V=O…HN hydrogen bonding. XRD,TG and DSC indicate that the lamellar structure of the V₂O₅ is preserved, PAn chains eliminate water form the interlamellar region and are partially inserted between the layers, and exist with extended-chain conformation owing to the confined environment.Electrochemical investigation in the range of 1.8³.8V (vs. Li) shows that PAn/V₂O₅ hybrid demonstrates substantially better reversibility and cycleability than V₂O₅ xerogel, which is attributed to the higher ion and/or electron transport and enhanced bidimensionality induced by incorporation of the polymer. In the PAn/V₂O₅ hybrid electrode, V₂O₅ is the major active substance, and the content,location,chain conjugation length and ordering of PAn are also factors of great importance. The optimal PAn/V₂O₅ hybrid exhibits an initial discharge capacity of 210mAh/g (0.8mA/cm2) with an average voltage of 2.78V (vs. Li), this leads to an energy density of 584Wh/kg. However, our datum show a slow but continued decrease in specific capacity and point out the need for an improved cycleability.