An Impedance Model for a Porous Intercalation Electrode with Mixed Conductivity

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A mathematical model for the impedance of porous intercalation electrodes of mixed conductivity has been derived. The model is based on an agglomerate model and dilute-solution theory. With respect to the impedance of similar electrodes of metallic conductivity, two corrections were identified. The first is related to the diffusional component of interparticle transport in the porous electrode. The second is an impedance related to the exchange of electrons with the electrode at the electrode–support interface. These two corrections may lead to significant deviations in the low frequency region of the impedance spectra of the mixed conductor. In the high frequency region, however, no significant differences were found between the impedance of the metallic electrode and that of mixed conductivity for similar parameter sets. Recombination of charge carriers in the system has been included through a spherical Gerischer impedance, giving rise to substantial deviations in the low frequency regions if reaction rates are significant.

©2009 The Electrochemical Society