Finite Element Modeling of Idealized Infiltrated Composite Solid Oxide Fuel Cell Cathodes

Abstract

Using a two-dimensional finite element approach, the polarization resistance of idealized, branched, nano-particulate, composite cathodes was determined. Porous CGO, LSGM, or YSZ networks infiltrated with additional ionic conductor and subsequently infiltrated with LSCF or BSCF were modeled. For fixed mixed conductor particle size, dual nano-particle infiltrations (ionic + mixed conductor) resulted in an order of magnitude polarization resistance decrease, compared to single component mixed conductor infiltrations. For most SOFC relevant temperatures (500-900C), geometries, and material combinations, cathode performance was limited by the charge transfer reaction occurring at the mixed conductor interface and therefore scaled with the cathode surface area, as long as the cathode thickness was <~10microns. For cathodes thicker than ~10microns, losses within the ionic conducting network determined performance, resulting in a breakdown of the linear performance dependence on cathode surface area. The boundary between these regimes varied with ionic conducting cathode arm width, column width, and ionic conductivity.