Liquid permeation through cast tape of graphite particles based on non-uniform packing structure

In the present study, the rate of liquid permeation is measured for green and pressed tapes used as an anode film of lithium ion battery. The tape was made of graphite particles of various shapes which were modified by high-speed rotational blending. The packing structure was measured by image analysis on the cross-sections of the tape in three dimensions and was characterized by a distribution of void sizes among particles. Based on the void size distribution, the mathematical model of permeation was developed considering the tape porous structure as the bundle of parallel pipes of various sizes. As a result, the liquid permeation data with the graphite tapes can successfully be described with the developed model, in contrast with much higher permeation rate by Kozeny–Carmanʹs equation. The permeation rate was also confirmed to get higher for the tape made of spherical particles as a result of higher equivalent diameter due to wider void size distribution and lower tortuosity owing to more regular packing structure.