A Precise, Reduced-Parameter Model of Thin Film Electrolyte Impedance
Date
2015-03-07
Journal Title
Journal ISSN
Volume Title
Publisher
The Electrochemical Society
Abstract
he extreme shape factors inherent in characterizing thin film electrolytes can present a challenge
to quantitative interpretation
f impedance spectra. Here, the impedance of a thin film ceramic electrolyte with surface
microelectrodes is modeled via direct umerical solution of current conservation. Faradaic and
non-faradaic currents at the electrode-electrolyte interface are modeled phe- omenologically using
a formulation based on the Butler-Volmer equation. The model is able to reproduce complex,
experimentally btained impedance spectra for Pt/YSZ and Pt/GDC cells using only four adjustable,
physically intuitive parameters: electrolyte onductivity, permittivity, exchange current density,
and double layer capacitance. Equivalent circuit models typically used to fit hese spectra instead
require six or more adjustable parameters with ambiguous physical meaning. Notably, the model
described here s able to capture a heretofore unexplained intermediate frequency arc seen in the
experimental results. A parametric study enables he mechanism of the intermediate frequency feature
to be identified as a spreading resistance in the electrolyte that vanishes at high requencies due
to low-impedance dielectric transport of current across the electrode-electrolyte interface. The
fitting results are validated by comparison of the parameter values with literature reports.
Description
Publisher's PDF.
Keywords
Citation
J. Electrochem. Soc. 2015 volume 162, issue 6, F537-F546