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XPS study of the Li intercalation process in sol–gel‐produced V 2 O 5 thin film: influence of substrate and film synthesis modification
Author(s) -
Ibris Neluta,
Salvi Anna Maria,
Liberatore Massimiliano,
Decker Franco,
Surca Angela
Publication year - 2005
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.2084
Subject(s) - x ray photoelectron spectroscopy , intercalation (chemistry) , lithium (medication) , substrate (aquarium) , materials science , thin film , vanadium , sol gel , electrochemistry , silicon , heterojunction , electrode , chemical engineering , analytical chemistry (journal) , inorganic chemistry , chemistry , nanotechnology , organic chemistry , medicine , oceanography , optoelectronics , geology , engineering , metallurgy , endocrinology
We report on the process of lithium intercalation in V 2 O 5 thin films deposited onto standard ITO‐coated glass substrates. The films were deposited via a well‐established sol–gel route, and the samples were examined as working electrodes in a range of potentials versus lithium reference electrode. This paper follows up issues arising from parallel spectroscopic characterizations of the films by X‐ray photoelectron spectroscopy (XPS). Specifically, the XPS examination showed that not all of the Li‐ion charge inserted was accounted for by the V(5) to V(4) reduction, but the stoichiometric balance could be maintained only by considering additional oxygens arising from the intercalation procedure, leading to Li 2 O formation. In this work, we have examined the possibility that the source of oxygen is the ITO substrate. To this purpose, films of V 2 O 5 deposited on silicon substrates have been prepared using the sol–gel process and examined by XPS after electrochemical intercalation/de‐intercalation cycles. We show that in this case a perfect balance between electrochemical charge, inserted Li and reduced vanadium is obtained. A further indication of ITO‐substrate effects was obtained from examination, by the same methods, of some unconventional V 2 O 5 films that had been co‐precipitated with a siloxane, designed to provide a template structure. The results obtained from this material imply that a barrier layer is formed at the ITO interface and, therefore, the formation of Li 2 O is avoided. The results are discussed in terms of the possible degradation of conventional V 2 O 5 on ITO as a result of electrochemically induced interface reactions. Copyright © 2005 John Wiley & Sons, Ltd.