The Relationship Between Nanoscale Structure and Electrochemical Properties of Vanadium Oxide Nanorolls

Authors


  • We thank Dr. Prikhodko in the Material Science and Engineering Department at UCLA for assistance with TEM. This work is supported by the Office of Naval Research through MURI grant N00014-01-1-0757. SHT is an Alfred P. Sloan Foundation research fellow.

Abstract

In this paper, we explore the relationship between the nanoscale structure and electrochemical performance of nanoscale scrolls of vanadium oxides (vanadium oxide nanorolls). The vanadium oxide nanorolls, which are synthesized through a ligand-assisted templating method, exhibit different morphologies and properties depending upon the synthetic conditions. Under highly reducing conditions, nearly perfect scrolls can be produced which have essentially no cracks in the walls (well-ordered nanorolls). If the materials are produced under less reducing conditions, nanorolls with many cracks in the oxide walls can be generated (defect-rich nanorolls). Both types of samples were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS) to characterize their local structure, local redox state, and nanoscale structure. After ion-exchange to replace the templating ammonium ions with Na+, the ability of these materials to electrochemically intercalate lithium reversibly was investigated. In sweep voltammetry experiments, the well-ordered nanorolls showed responses similar to those seen in crystalline orthorhombic V2O5. In contrast, the defect-rich vanadium oxide nanorolls behaved electrochemically more like sol–gel-prepared vanadium oxide materials. Moreover, the specific capacity of the well-ordered nanorolls was about 240 mA h g–1 while that of the defect rich nanorolls was found to be as much as 340 mA h g–1 under these same conditions. Disorders on both the atomic and nanometer length scales are believed to contribute to this difference.

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