Kinetic Study of Li_xWO₃ Electrochromism

Abstract

Coloring/bleaching processes of Li x WO3 electrochromism were examined in terms of emf, chronoamperometry, voltammetry and ac impedance measurements. The current-potential relation was found to be ohmic in the short time region and expressed by i=(E app-emf (x))/R. Satisfactory fittings were obtained for chronoamperometry and voltammetry measurements on the basis of the assumption of diffusion-limited process with above i-E relation. Diffusion coefficient was estimated to be about 5×10-10 cm2/sec. It was elucidated from the detailed analysis of impedance that R was given by the summation of the resistances of solution, electrode, charge transfer and material transfer. Since it was found that the WO3 film was regarded as a large condenser with a serially connected resistor, color/bleach processes were understood as charging/discharging processes of WO3 film.

Analysis of cyclic voltammograms of electrochromic a-WO3 films from voltage-dependent equilibrium capacitance measurements

“…In this paper we apply this type of analysis to investigate the principal features of CVs of lithium intercalation and deintercalation in thin electrochromic films based on a-WO 3 . Nagai and Kamimori [8] also studied the implication of the underlying electrochemical mechanisms on CVs shapes, attempting to provide a simplified equivalent circuit that accounts for them. Here we show first, the determination of chemical capacitance from measurements in galvanostatic quasiequilibrium conditions.…”

Thermo Optic Coefficients and Electronic Polarizabilities of Tungsten Bronzes Using Ellipsometry

“…The density of evaporated WO 3 was determined to be 6.0 ± 0.3 gm/c.c [41], [47]. Tungsten oxide films evaporated from WO 3 powder (at room temperature) have been reported to be defect compounds of the type WO 3−y , and the stoichiometry of the evaporated WO 3 thin films was reported to be ∼2.72 (O/W ratio) by many workers [from different techniques, e.g., Proton backscattering, Auger electron spectroscopy (AES) and Electron spectroscopy for chemical analysis (ESCA)] [52]- [54].…”

Dynamics in Electrochromic Windows Interpreted with an Extended Logistic Model

“…The time dependence of the coloration of amorphous WO 3 at low voltages was described in terms of a barrier for current at the WO 3 -electrolyte interface. 2,3 The coloring and bleaching processes of Li x WO 3 films were examined in short time ranges considering diffusion-limited process, 4 whereas the kinetics of electrochemical reactions in WO 3 was found to be governed by the resistance that depends on the conductivity of electrolyte, reduced forms of WO 3 and transparent conducting layers. 5 The ion transport in host electrodes was reviewed in Refs.…”