3. Electrode modeling

3.1 Characterization of porous media

The electrode of a lithium-ion battery is a composite porous medium consisting of an active material (graphite on the negative side or lithium metal oxide on the positive side), a conductive additive (carbon black) and a binder. The electrolyte fills the pores of this solid matrix. The porosity of the electrode substantially increases its active surface, enabling it to deliver high currents.

The porous electrode is not easy to model, however, as the pores are not uniform in size. The volume fraction of the electrolyte varies within the electrode, as does the volume fraction of the solid matrix. Electrode properties (electrical conductivity and ionic transport) are necessarily affected by these variations. For this reason,...