Three-dimensional conductivity model for porous electrodes in lead acid batteries

In this paper, the critical volume fraction (CVF) of electrodes having porosity is predicted with the help of a three-dimensional (3D) conductivity model. The model consists of a 3D lattice of nodes; which in this paper, are assumed to be identical spheres, which are in electrical contact with their neighbors. The porosity that exists between these spheres is referred to as “micro-porosity” while the porosity that occurs from having missing spheres is referred to as “macro-porosity”. The critical volume fraction is the maximum utilization of an electrode's active material and occurs when the electrode's conductivity changes from being conductive to nonconductive. Previous 3D conductivity models used to determine the CVF did not account for porosity. The porosity is modeled from porosity size distribution previously determined experimentally by other researchers.