Structural and Electrochemical Behaviour of Sputtered Vanadium Oxide Films: Oxygen Non-stoichiometry and Lithium Ion Sequestration

Rao, KJ and Pecquenard, B and Gies, A and Levasseur, A and Etourneau, J (2006) Structural and Electrochemical Behaviour of Sputtered Vanadium Oxide Films: Oxygen Non-stoichiometry and Lithium Ion Sequestration. In: Bulletin of Materials Science, 29 (5). pp. 535-546.

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Abstract

Structural and electrochemical aspects of vanadium oxide films recently reported from ICMCB/ENSCPB have been examined using appropriate structural models. It is shown that amorphous films are nonstoichiometric as a result of pre-deposition decomposition of $V_2O_5$. It is proposed that the structure of amorphous films corresponds to a nanotextured mosaic of $V_2O_5$ and $V_2O_4$ regions. Lithium intercalation into these regions is considered to occur sequentially and determined by differences in group electronegativities. Open circuit voltages (OCV) have been calculated for various stoichiometric levels of lithiation using available thermodynamic data with approximate corrections. Sequestration of lithium observed in experiments is shown to be an interfacial phenomenon. X-ray photoelectron spectroscopic observation of the formation of $V^{3+}$ even when $V^{5+}$ has not been completely reduced to $V^{4+}$ is shown to be entirely consistent with the proposed structural model and a consequence of initial oxygen nonstoichiometry. Based on the structural data available on $V_2O_5$ and its lithiated products, it is argued that the geometry of $VO_n$ polyhedron changes from square pyramid to trigonal bipyramid to octahedron with increase of lithiation. A molecular orbital based energy band diagram is presented which suggests that lithiated vanadium oxides, $Li_xV_2O_5$, become metallic for high values of x.

Item Type:	Journal Article
Publication:	Bulletin of Materials Science
Publisher:	Indian Academy of Sciences
Additional Information:	Copyright of this article belongs to Indian Academy of Sciences.
Keywords:	Amorphous films;Vanadium oxide films;Structural and electrochemical properties.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	13 Dec 2006
Last Modified:	19 Sep 2010 04:33
URI:	http://eprints.iisc.ac.in/id/eprint/9087

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