Two methods were developed to create microporous membranes of vanadium pentoxide (V2O5). In one method, the membranes were made from aqueous solutions of V2O5 polymers by phase inversion in acetone. Subsequent supercritical drying removed liquid from the pores to yield a V2O5 aerogel with a specific surface area of 165 ± 30 m2/g and a mean pore diameter near 50 nm. However, air-drying destroyed the pore structure to produce a dense V2O5 xerogel with a surface area under 10 m2/g. The second method eliminated the need for supercritical drying. The phase inversion of aqueous solutions of V2O5 polymers now occurred in a mixture of acetone and propylene carbonate. Partial air-drying removed the acetone, but not the liquid propylene carbonate. The resulting V2O5 was a wet gel with a specific surface area of 270 ± 70 m2/g and a mean pore diameter near 40 nm. Scanning electron micrographs of the V2O5 gels made by the first and second method showed similar microstructures with randomly entangled fibers. Electrochemical characterization of both materials suggested their performance as cathodes in lithium batteries is limited by electronic conductivity rather than lithium diffusion.
Bibliographical noteFunding Information:
Sameer Desai took the micrographs. M.G.K. is grateful to the National Chemical Laboratory, Pune, India, for a leave. This paper was largely supported by the Defense Advanced Research Projects Agency DARPA Grant 92-05112. Other support came from the National Science Foundation (Grants CTS 95-38755).
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