Percolation Theory in Solid Oxide Fuel Cell Composite Electrodes with a Mixed Electronic and Ionic Conductor

Abstract

Percolation theory is generalized to predict the effective properties of specific solid oxide fuel cell composite electrodes, which consist of a pure ion conducting material (e.g., YSZ or GDC) and a mixed electron and ion conducting material (e.g., LSCF, LSCM or CeO 2 ). The investigated properties include the probabilities of an LSCF particle belonging to the electron and ion conducting paths, percolated three-phase-boundary electrochemical reaction sites, which are based on different assumptions, the exposed LSCF surface electrochemical reaction sites and the revised expressions for the inter-particle ionic conductivities among LSCF and YSZ materials. The effects of the microstructure parameters, such as the volume fraction of the LSCF material, the particle size distributions of both the LSCF and YSZ materials (i.e., the mean particle radii and the non-dimensional standard deviations, which represent the particle size distributions) and the porosity are studied. Finally, all of the calculated results are presented in non-dimensional forms to provide generality for practical application. Based on these results, the relevant properties can be easily evaluated, and the microstructure parameters and intrinsic properties of each material are specified.Keywords: solid oxide fuel cell; percolation theory; mixed electron and ion conductor; LSCF; coordination number; three-phase-boundary sites; electrochemically active sites

Optimization of the Interconnect Ribs for a Cathode-Supported Solid Oxide Fuel Cell

“…The coordination number theory based percolation micro-model reveals the relationship between the effective electrode properties and the microstructure parameters [36][37][38][39]. Considering a binary system with random packing of spheres, corresponding to the electrode-particles (denoted as el) and electrolyte-particles (denoted as io), The effective electric conductivity of k-phase is estimated as [40]:…”

“…where 0 k σ is the electric conductivity of k-material in dense solid; k φ the volume fractions of k -particles in the solid structure; t k φ is the threshold volume fraction of k-particles, which is determined by [35,38] …”

Stochastic geometrical modeling of solid oxide cells electrodes validated on 3D reconstructions

“…Nevertheless, the electrodes present a complex three dimensional microstructure for which the basic relationships between the three-dimensional characteristics of the microstructure and the electrode properties are not still precisely understood. Thus, 3 several studies [11][12][13][14] have been recently proposed in an attempt to improve the knowledge of such relations, which are essential before optimizing the microstructure.…”

“…In general, the evolution of microstructural parameters such as the specific surface area, the tortuosity factor or the Triple Phase Boundaries lengths TPBls (defined as the lines where the electronic, ionic and gas phase meet) are plotted as function of the phase volume fractions with few points [23,24]. These data are thus insufficient to fully understand and validate the proposed complex relationships linking the electrode microstructure parameters [11,13]. In order to increase the amount of data required to fit accurately these relationships, an alternative method consists of generating representative synthetic microstructures by numerical means.…”

Thermal conductivity prediction of closed-cell aluminum alloy considering micropore effect

“…4 For the random dispersion of two School of Power Engineering, Jiangsu University of Science and Technology, Zhenjiang, China components, the effective conductivity is modeled well by the EMT equation. 8 However, the aforementioned models are only applicative in single porosity situation, namely, the porous media with relatively uniform pore distribution. The dual-porosity model has already been successfully used in explaining the soil infiltration mechanism.…”