Analysis of cyclic voltammograms of electrochromic a-WO3 films from voltage-dependent equilibrium capacitance measurements |
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Authors: | Jorge García-Cañadas Ivan Mora-Seró Francisco Fabregat-Santiago Juan Bisquert Germà Garcia-Belmonte |
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Affiliation: | Departament de Ciències Experimentals, Universitat Jaume I, Campus del Riu Sec, E-12080 Castelló, Spain |
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Abstract: | The main features of cyclic voltammograms (CVs) of thin electrochromic films based on a-WO3 were investigated. First, the chemical capacitance is defined in terms of the electrochemical potential variation with the insertion level, x, and is measured under galvanostatic (chronopotentiometry) quasi-equilibrium conditions. An equilibrium capacitance increasing rapidly with respect to insertion level or negative potential is observed, respectively Cch∝xa at x>10?3(a≈0.74) and Cch∝Vα(α≈3). Simulation methods used to generate the observed CVs are described in detail. Major CV peaks can be simply understood as charging and discharging of the variable capacitor, in conjunction with a distortion of the voltage scale due to a series transport process. Therefore a simple RC equivalent circuit allows us to explain the principal CVs characteristics of lithium intercalation and deintercalation in amorphous films. |
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Keywords: | Chronopotentiometry Voltammetry Electrochromic films Capacitance Equivalent circuit |
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