Published online by Cambridge University Press: 25 February 2011
Vanadium pentoxide gels V2O5·nH2O are actually hydrous oxides. Water adsorption and dissociation occurs at the surface of the oxide leading to negatively charged oxide particles surrounded by an acid aqueous medium. Ionic conductivity is observed, arising from proton diffusion through the water molecules. This process mainly depends on the nature of adsorbed water molecules. Proton conductivity is strongly related to the water adsorption isotherm.
Ion exchange readily occurs at the oxide-solution interface when the gel is dipped into an aqueous solution of a metal chloride. New vanadium bronzes have been obtained upon heating such gels around 300° C. They exhibit interesting properties as reversible cathodes.
Electrochemical insertion of Li* into the gel phase is quite easy. This is due to the very open structure of the gel and the mixed valence behavior of the vanadium oxide.
Transition metal oxide gels could then be used as thin films or pressed pellets for making micro-ionic devices.