PERMEATION OF FLUIDS IN POROUS PARTICULATE ELECTRODES - A PERCOLATION MODEL

Permeation of fluids (electrolytes and gases) in porous/particulate systems is important in batteries, fuel cells and other electrochemical reactors. A percolation model is proposed which describes the electrocapillary equilibrium in porous networks. Based on a set of doubly discrete non-linear difference equations, the local and global levels of flooding are numerically computed as a function of the bonds-filling factor p which incorporates system/input parameters such as electrode potentials, pressure differentials across fluid phase boundaries, electrocapillary characteristics and pore size distribution. A percolation threshold is identified at a value of p different from that corresponding to the infinite lattice. Differences between semi-infinite porous electrodes and infinite lattices are highlighted. The notion of a ''flooded porous electrode'' is sharpened. For non-wetting fluids, the possibility of an interesting transition is predicted which switches the porous electrode from a state of complete flooding to one