Lithium-ion battery electrode as a cohesive granular material

International audienceLi-ion Batteries finds their application in a wide range of industrial and customer products. Their performances, such as charging rate and energy storage capacity, are highly influenced by the microstructure of the electrodes, and thus the manufacturing process. For modern batteries, it involves a compaction step called calendering where the thickness of the electrode is reduced between two cylinders in order to increase its density. However, this compaction step increases also the tortuosity of the electrode, which decreases the final charging rate of the battery ; thus, a compromise is necessary between energy storage and charging rate. Simulations are a useful tool to investigate this compromise and better understand the link between grains properties, operational parameters and final electrodes properties and performance.The microstructure of the electrode involves a granular media, therefore its behaviour is here simulated using the Discrete Element Method. The models usually employed in the literature lack of some physics as they tend to misrepresent the cohesive and plastic aspects of the grains and binder. We developed and tested a new contact law dedicated to Li-Ion battery which allows to implicitly take into account the presence of the binder and its mechanical contribution. Moreover the simulations performed here use a direct simulation of the calendering rolls, whereas studies from the literature use an uniaxial compression approximation.We tested and validated our contact law against experimental data and tested the influence of operational parameters such as calendering speed and loading. We observe a huge impact of the applied loading on the electrode properties, but no significant impact of the calendering speed as long as the speed is relatively low. We show that this model can be used to predict correctly the final properties of the electrode based on its composition and the calendering parameters used