SYNTHESIS AND CHARACTERIZATION OF POLYPYRROLE VANADIUM PENTOXIDE NANOCOMPOSITE AEROGELS

Vanadium pentoxide/polypyrrole aerogel (ARG) composites have been synt hesized by sol-gel routes, ana investigated as cathode materials in Li batteries. The primary method utilized simultaneous polymerisation of pyrrole and vanadium alkoxide precursors. Hydrolysis of VO(OC3H7)(3) using pyrrole-water-acetone mixtures yielded monolithic green-black ge ls with polypyrrole/V ratios ranging from 0.15 to 1.0. Supercritical d rying yielded high surface (150-257 m(2) g(-1)) aerogels with densitie s between 0.1 and 0.2 g cm(-3), that were of sufficient mechanical int egrity to allow them to be cut without fracturing. TEM studies of the ARGs show that they are comprised of fibers similar to that of V2O5 AR Gs, but with a significantly shorter chain length. The interaction bet ween the polypyrrole (PPy) and V2O5 aerogel in the nanocomposites was probed using IR spectroscopy. Our results suggest that the inorganic a nd organic components strongly interact during the initial stages, thu s perhaps impeding the vanadium condensation process. Hence, the PPy/V 2O5 nanocomposites exhibited lower electrical conductivity with increa sed polypyrrole content. The addition of(NH4)(2)S2O8 as an oxidizing a gent improved the conductivity of the nanocomposites. The deleterious effect of the conductive polymer on the bulk conductivity does not nec essarily affect the electrochemical properties of these materials; Nan ocomposite materials that were subjected to post-oxidative treatment s how enhanced Li insertion capacity compared to the pristine ARG. The p hysical properties of these 'nanocomposite aerogels' are different fro m 'microcomposites' prepared by an alternate route, in which the oxide gel is formed in the presence of a dispersion of-preformed micrometer -sized polypyrrole particles.