Characterisation of sol–gel crystalline V<sub>2</sub>O<sub>5</sub> thin films after Li intercalation cycling

Alamarguy, David; Castle, J. E.; Ibriş, Neluţă; Salvi, Anna Maria

doi:10.1002/sia.2138

Cited by 14 publications

(9 citation statements)

References 4 publications

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“…Work that considers the use of spectroscopic and microscopic techniques at very high resolution is in progress to better investigate the lateral and in-depth homogeneity of such electrodes in the as-received state and after use. 35 …”

Section: Discussionmentioning

confidence: 97%

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

Ibriş

Salvi

Liberatore

et al. 2005

Surf. Interface Anal.

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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.

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Section: Discussionmentioning

confidence: 97%

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

Ibriş

Salvi

Liberatore

et al. 2005

Surf. Interface Anal.

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“…15 Four samples were prepared by electrochemical cycling at a rate of 0.5 mV/ s, over the range 3.7 V -3.0 V -3.7 V, using a solution of lithium perchlorate in propylene carbonate as the electrolyte and lithium foil for counter-and reference electrodes. 15 Four samples were prepared by electrochemical cycling at a rate of 0.5 mV/ s, over the range 3.7 V -3.0 V -3.7 V, using a solution of lithium perchlorate in propylene carbonate as the electrolyte and lithium foil for counter-and reference electrodes.…”

Section: B Electrochemistrymentioning

confidence: 99%

Factors influencing charge capacity of vanadium pentoxide thin films during lithium ion intercalation/deintercalation cycles

Alamarguy

Castle

Ibriş

et al. 2007

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The intercalation of vanadium pentoxide by lithium ions leads to a change in optical properties, a process that is of value in thin-film electrochromic devices. In this study, films of V 2 O 5 , deposited on indium tin oxide ͑ITO͒ glass coupons by a sol-gel process, were challenged by increasing numbers of charge-discharge cycles ranging from 72 to 589 full cycles. The samples were characterized by x-ray photoelectron spectroscopy ͑XPS͒ and then examined in the deintercalated state by time-of-flight secondary ion mass spectroscopy ͑SIMS͒. XPS enabled measurement of the thickness and composition of the solid-electrolyte interface and provided evidence of the residual V 4+ concentration within the top few nanometers of the surface. The SIMS profile gave direct information on the thickness of the films and on the thickness loss caused by rinsing the samples after the electrochemical exposure. Determination, by SIMS, of the concentration of lithium ions has enabled a correction to be made for the amount of inactive material within the electrochemically active region of the film. The SIMS depth profiles for lithium in the four samples are similar, with a marked buildup of Li at the interface with the ITO. This interphase zone had a thickness of ϳ27 nm and was electrochemically inactive, enabling a further correction to be made. Thus, by means of the XPS and the SIMS results the chemistry and thickness of the films could be fully characterized. The remaining inconsistency between capacity ͑between 35% and 100% of the anticipated charge͒ and number of cycles is ascribed to edge effects arising from the method used for production of the coupons.

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“…The study of lithium-ion chemistry at the buried interface is made difficult by its lack of an Auger electron emission and its weak signal in x-ray photoelectron spectroscopy (XPS). Secondary ion mass spectrometry (SIMS), however, has an excellent sensitivity to Li [3,4] and this article reports on an investigation of the behaviour of lithium ions at the ITO/V 2 O 5 interface using SIMS-depth profiling. The lithium ions were introduced by the widely used technique of electrochemical insertion from a non-aqueous electrolyte and continues an investigation of the Li-V 2 O 5 system by electrochemical and XPS characterisation.…”

Section: Introductionmentioning

confidence: 99%

“…[4] The SIMS profiling was validated by the non-invasive technique of proton-beam reaction profiling: Lithium is identified by the alpha particles emitted from the 7 Li (p, α) reaction [7] and had a bimodal energy distribution corresponding to Li at the surface and the interface. This technique also confirmed the finding of Li in the interface of the non-immersed region of the test piece.…”

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confidence: 99%

XPS and TOF‐SIMS study of the distribution of Li ions in thin films of vanadium pentoxide after electrochemical intercalation

Castle

Decker

Salvi

et al. 2008

Surface & Interface Analysis

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The intercalation of vanadium pentoxide by lithium ions leads to a change in optical properties, a process that is of value in thin-film electrochromic devices. The extent of intercalation can be measured, electrochemically, from the charge capacity of the film and, is in good agreement with that determined in the outermost layers by X-ray photoelectron spectroscopy (XPS), when intercalation occurs homogeneously through the film thickness. SIMS profiles of V 2 O 5 -deposited on ITO-glass coupons have allowed examination of the interface between these layers and in prior work showed a marked build up of Li in this interphase. Investigation of the distribution of lithium within the interphase showed it to be present in parts of the testpiece that were not immersed in the electrolyte used for Li insertion. In this work we have tested the suggestion that the lithium found in the interface can be introduced, during intercalation, via the exposed edge of the V 2 O 5 /ITO interface at the periphery of the sample. A series of intercalation cycles using modified cells to expose either: a) the periphery; or b) the centre; of the thin film have been carried out. The distribution of lithium after intercalation has been examined using a combination of ToF-SIMS and XPS. XPS showed lithium in the film to be related only to the immersed regions of the testpiece whilst SIMS profiles confirmed the widespread distribution of Li through the interface, only when an edge was exposed. We work confirms an important influence of an unsealed edge when samples are produced by cutting from larger glass plates.

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Characterisation of sol–gel crystalline V₂O₅ thin films after Li intercalation cycling

Cited by 14 publications

References 4 publications

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

Factors influencing charge capacity of vanadium pentoxide thin films during lithium ion intercalation/deintercalation cycles

XPS and TOF‐SIMS study of the distribution of Li ions in thin films of vanadium pentoxide after electrochemical intercalation

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Characterisation of sol–gel crystalline V2O5 thin films after Li intercalation cycling

Cited by 14 publications

References 4 publications

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

XPS study of the Li intercalation process in sol-gel-produced V2O5 thin film: influence of substrate and film synthesis modification

Factors influencing charge capacity of vanadium pentoxide thin films during lithium ion intercalation/deintercalation cycles

XPS and TOF‐SIMS study of the distribution of Li ions in thin films of vanadium pentoxide after electrochemical intercalation

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Characterisation of sol–gel crystalline V₂O₅ thin films after Li intercalation cycling