Simulation of the calendering process of lithium-ion battery electrodes: evolution of porosity

The electrical properties of Lithium-ion batteries are not only given by their composition, but also by how they are manufactured. The calendering process is an important step of their fabrication, as it will greatly change the internal microstructure of the electrodes and can lead to batteries with completely different properties. We present here a new numerical model using the Discrete Element Method (DEM) to simulate the calendering process of lithium-ion battery electrodes. By introducing the calendering rolls in the simulations, it allows for a more realistic representation of the process with the electrode moving between the rolls, therefore improving the previous calendering models. The study focuses on the influence of the initial microstructure and the calendering parameters on the final characteristics of the electrode, such as porosity and electrical and ionic conductivities. Electrodes with various initial porosities are tested, as well as different calendering speeds and loadings. The first results show that under high calendering compression and without grain breakage, the final porosity of the electrode does not depend on the initial porosity. As expected, the movement of the particles inside the electrode is here more complex than under purely vertical compression, due to the rotation of the rolls. The findings will be used in the future to build a numerical model predicting the final battery properties depending on the composition of the electrodes and the calendering parameters.