3D-Modelling and Performance Evaluation of Mixed Conducting (MIEC) Cathodes

Abstract

Mixed electronic/ionic conducting (MIEC) cathode materials are qualified for the application in intermediate-temperature SOFCs. The area specific resistance of MIEC cathodes is likewise determined by chemical composition and microstructure. A three-dimensional finite element method model, which is capable to analyze and predict the performance of MIEC cathodes, was developed. Representations for the actual cathode microstructure are automatically generated according to characteristic measures like cathode thickness, composition, porosity and average particle size. The model calculates the spatial distributions of the oxygen activity, the diffusive oxygen flux in the pores as well as the ionic current density inside the MIEC-cathode and inside the electrolyte material. Based on these values the area specific resistance of the cathode and the penetration depth of the ionic current can be evaluated. This paper will analyze the effect of surface-exchange kO and bulk-diffusion coefficient DO as well as the influence of microstructure properties on the cathode performance.

Progress in 3D electrode microstructure modelling for fuel cells and batteries: transport and electrochemical performance

“…The popularity of FEM in the electrochemical energy community has been boosted by the widespread use of commercial software, among which COMSOL Multiphysics [127] is probably the most popular one for electrochemistry [33,98,111,114,116,[128][129][130][131][132][133][134][135][136][137]. Nonetheless, open-source codes based on deal.ii library [138], such as OpenFCST [99] and ParCell3D [115,139], Sandia's Sierra…”

“…Nevertheless, FEM is useful when more physics are simulated together, such as different transport mechanisms occurring in different domains coupled by interfacial (or TPB) charge-transfer kinetics. This is the standard problem simulated in all the microstructure-resolved 3D electrochemical models [98,99,115,116,118,128,132,136,137,139]. Conversely, multiple parallel reaction pathways are seldom considered.…”

Electrochemical Performance of Nanoscaled La0.6Sr0.4CoO3-δ as Intermediate Temperature SOFC Cathode

“…All these parameters are material related and were taken from (12). The term r O ⋅ (α f + α b ) equals k*⋅ c mc and is therefore related to the surface exchange coefficient k* obtained by 18 O 2 -exchange experiments, with c mc being the concentration of oxygen lattice sites in the MIEC material. The solid phase tortuosity τ and the volume specific surface area a are geometry related parameters and were calculated with the aid of a 3D finite element method (FEM) microstructure model (18).…”

Oxygen Surface Exchange and Bulk Diffusion Coefficients Evaluated from Porous Mixed Ionic-Electronic Conducting Cathodes

“…1 a). The parameters tortuosity and surface area were calculated for different porosity (ε) and particle size (ps) combinations with a 3D FEM microstructure model (18). Values for oxygen lattice sites, O 2-concentration and the thermodynamic factor were taken from literature.…”