Dynamic Processes in the Coloration of WO[sub 3] by Lithium Insertion

Abstract

Electrochemical impedance spectroscopy was used in the study of lithium insertion in a WO3 film. Spectra obtained at different potentials showed the characteristic shape of a diffusion process, with a Warburg regime at high frequencies and a capacitive branch at low frequencies arising from the charge storage associated with the intercalation of Li+. But the low frequency wing showed, as in many other reports, a pronounced dispersion which could not be accounted for solely by the diffusion capacitance. The possibility of an additional kinetic process was investigated. A number of models accounting for such effect were considered, including the constant phase element restricted diffusion model that differentiates diffusion from blocking effects and another model with fast and slow charging processes. The evolution of the impedance with charge-discharge cycles was considered as well. It was found that a suitable interpretation of the experimental results is provided by a new model that considers the coupling of diffusion and the solid-state reaction whereby inserted ions are incorporated in fixed sites of the lattice. This model could be further elaborated on the basis of a diffusion and multiple trapping scheme, which provides an ordinary or Warburg diffusion region in the range of highest frequencies, and additional components at lower frequencies which reflect the kinetics of the ion immobilizing process, and which in some cases show an anomalous diffusion pattern. This explanation was found consistent with the results of complementary techniques of measurement such as the electro-optical transfer function. © 2001 The Electrochemical Society. All rights reserved.

Study of the lithium insertion–deinsertion mechanism in nanocrystalline γ-Fe2O3 electrodes by means of electrochemical impedance spectroscopy

“…12 a, b, c and d respectively. The n value remains sensibly constant over the whole OCV range at a value similar to that obtained by Bisquert et al [38]. In the case of fitted ω d , a sensibly constant value was observed for the discharged battery down to about 2.6 V vs. Li + /Li (Fig.…”

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Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping

“…Ion-trapping in a host material is a complex phenomenon and coupled to a variety of processes occurring in the solid state. [15][16][17] For lithium intercalation in metal oxides, a widely adopted picture considers two main limiting steps for the kinetics: 18 (i) the overcoming of a barrier at the ion injection interface (the electrolyte/TiO 2 interface), and…”

Voltammetric and Electrochemical Impedance Spectroscopy Study of Prussian Blue/Polyamidoamine Dendrimer Films on Optically Transparent Electrodes

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