Coupled numerical simulation of the drying and calendering for Lithium-ion battery anodes with non-spherical particles
Mark Lippke, Caroline Willuhn, Tobias Ohnimus, Thilo Heckmann, Philip Scharfer, Wilhelm Schabel, Carsten Schilde, Arno Kwade
Abstract
As the drying and calendering processes are crucial to the resulting electrode microstructure and, therefore, electrode performance, various approaches have been developed for modeling these two processes. In this work, the drying and calendering processes of graphite anodes were modeled using the Discrete Element Method to predict the anode microstructure, inactive material distribution and final film thickness. The drying model comprised a drying-kinetic model, a binder model, and a structure-oriented model. Calendering was modeled using anode structures obtained from the drying model. Although drying and calendering has been modeled for spherical cathode active materials, the modeling of irregular graphite particles is much more challenging. Unprecedentedly, in this study, the flake-like shape of the graphite particles was considered. While the drying model was able to accurately predict coating thickness and porosity, the calendering model was able to reproduce experimental calendering results up to a moderate degree of compaction. Finally, the deformation behavior of graphite anodes was investigated experimentally. It was found that beyond a certain calendering stress of approximately 5 MPa, further anode deformation is completely plastic. This was identified as the reason for the calendering model limitations. Ideas for contact model modifications were suggested. • Coupling of different modeling techniques for anode production. • Approach that covers kinetics, structure formation and binder migration. • Explicit consideration of particle shapes on calendering behavior.