Issue 24, 2003

Surface analyses of In–V oxide films aged electrochemically by Li insertion reactions

Abstract

The surface of a Li-insertion In–V mixed-oxide electrode and the evolution of its composition and morphology upon prolonged intercalation/deintercalation cycles have been studied by a combination of the following bulk and surface-sensitive analytical techniques: Electrochemical analysis (cyclic voltammetry, impedance spectroscopy), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning photoelectron spectromicroscopy (SPEM). The In–V oxide film, obtained by rf sputtering as a thin film on conductive glass for use as a transparent electrode in electrochromic windows, is a Li-insertion material with good reversibility and high charge capacity, having a surface morphology characterised by a low initial roughness. XPS results showed that Li+-insertion brought about the reduction of V5+ to V4+ and V3+, with the onset of new structures in the valence band, related to the formation of Li2CO3 on the electrode surface. Such chemical changes were largely reversed upon Li-deinsertion and only a barely detectable effect on the surface morphology was seen after up to ten cycles. Extensive Li-charge–discharge cycling induced larger changes in the electrode morphology (increase in grain size and roughness), in the surface composition and microscopic aspect, with a partial passivation effect on the film electrochemical behaviour. The formation of surface deposits with a characteristic, elongated shape has been revealed to occur after 500 Li charge–discharge cycles. Submicron chemical analysis of such deposits onto aged oxide electrodes has been performed by SPEM, which enabled the location and assignment of the surface composition.

Article information

Article type
Paper
Submitted
16 Jun 2003
Accepted
27 Oct 2003
First published
14 Nov 2003

Phys. Chem. Chem. Phys., 2003,5, 5489-5498

Surface analyses of In–V oxide films aged electrochemically by Li insertion reactions

C. Coluzza, N. Cimino, F. Decker, G. Di Santo, M. Liberatore, R. Zanoni, M. Bertolo and S. La Rosa, Phys. Chem. Chem. Phys., 2003, 5, 5489 DOI: 10.1039/B306800E

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