V2O5 aerogel as a versatile host for metal ions

Vanadium pentoxide aerogels have the ability to electrochemically insert a wide variety of metal ions. This paper describes the reversible insertion of Na+, K+, Mg2+, and Ba2+: these ions represent a progression of ion size and charge. A critical factor in their insertion is the role of surface morphology, as it appears that divalent insertion, in particular, is associated with the high surface area of the aerogel. In nearly all cases, the amount of reversible insertion greatly exceeds values reported for other materials. Moreover, this is the first report of reversible electrochemical insertion of Ba2+ in solids. The measurements indicate a general trend of lower specific energy density as charge increases. (C) 2004 Elsevier B.V. All rights reserved.