CALCULATION OF CONDUCTIVITY AND POLARIZATION RESISTANCE OF COMPOSITE SOFC ELECTRODES FROM RANDOM RESISTOR NETWORKS

A model for total conductivity and polarization resistance of composite electrodes in solid oxide fuel cells is proposed. The model is based on numerically solving Kirchoff's current law for the resistor network resulting from scattering predetermined fractions of electrode and electrolyte particles at random on the sites of a three-dimensional cubic lattice. The model predicts an almost abrupt rise in total conductivity at an electrode-particle volume-fraction of 0.3, and a polarization resistance with a relatively broad minimum close to this percolation threshold, in good agreement with experimental results.