Preheating of Lithium-Ion Battery Electrodes as Basis for Heated Calendering: A Numerical Approach

Lithium-ion batteries are state of the art and, still, their performance is constantly improving. To increase the energy density and electric conductivity, electrodes are usually calendered. Hereby, a higher degree of compaction, while reducing structural damage, can be reached by heating the calendering rolls. For industrially relevant line speeds, it is however questionable whether the contact time between electrode and roll is sufficient to reach the full positive effect of the increased temperature. This study shows a numerical approach based on the discrete element method to simulate the heating behavior of electrodes before and during calendering using a typical NMC-622-cathode as a model structure. To improve the results of existing, more simplified discrete element method simulations, which neglect the heat transfer through the carbon black–binder matrix, an extension with heat transfer through the carbon black–binder matrix has been implemented. Considering process parameters, such as calender roll temperature and line speed, as well as electrode parameters, such as thickness and porosity, this model can provide an individual calculation of the heating behavior to evaluate the need for a preheating device. Specifically, this study provides an in depth analysis of the influence of the mass loading on the heating time. It becomes clear that preheating can be of great relevance especially for high mass loadings, as well as high line speeds, as the required heating time increases by 116% when the basis weight is increased by 50%.