Model Development for Binder Migration within Lithium-Ion Battery Electrodes during the Drying Process

Abstract

In the drying process of electrodes for lithium-ion batteries, the layer structure is defined and can only be influenced slightly in the subsequent process steps. An essential point in the drying process is the fixation of the binder, ensuring both the adhesive and cohesive strength of the electrode. It is known that high drying rates lead to the segregation of the binder in the direction of the coating surface, which results in reduced mechanical stability of the electrode. In a previous publication, an experimental approach was used to investigate the underlying processes that influence binder migration. These results are now used in a model-based approach to describe the binder migration using the convection–diffusion equation. The convective term originates from the shrinkage behavior of the layer during drying due to the relative movement between the active material particles and the solvent in which the binder is dissolved or dispersed; it is expected to be the cause of the binder migration. The diffusive term, representing the binder movement in the solvent, counteracts segregation. The interaction of these forces is simulated at different drying temperatures and the associated drying rates.