MONTE-CARLO SIMULATIONS OF POLARIZATION RESISTANCE OF COMPOSITE ELECTRODES FOR SOLID OXIDE FUEL-CELLS

The polarization resistance of composite electrodes for solid oxide fu el cells was modeled by three-dimensional random-resistor networks. Th ese were generated on a computer by identifying neighbors in cubic lat tices randomly occupied by electrolyte particles (ionic conductors) or electrode particles (electronic conductors), or in random packings ge nerated by sequential deposition of such particles in random order. Th e polarization resistances between electrode and electrolyte particles were taken to be in parallel with interfacial capacitances, and the p olarization resistance of the composite was calculated as the differen ce between high- and low-frequency resistance of the resistor networks . The volume fraction of electrode particles at which the minimum in p olarization resistance occurs was found to increase with the ratio bet ween electrode-particle radius and electrolyte-particle radius. This w as rationalized by investigating the limits within which the composite may be expected to contain electrode-electrolyte interfaces in which both the participating clusters extend throughout the composite. if su ch interfaces are present, there will be a thickness dependence in the polarization resistance to a degree depending on the component conduc tivities and polarization conductances, otherwise not. The results are in reasonable agreement with experimental data.