The fast-charging capability of lithium-ion batteries (LIBs) is significantly influenced by the microstructure of the electrode materials. During the electrode production process, the microstructure is significantly influenced by the calendering step, that involves the compression of electrodes between two rollers. This process step alters the density, porosity and particle orientation as well as the tortuosity, and impacts also the electrode mechanics. However, the extend of the microstructure altering during the calendering process is highly dependent on the electrode composition, especially from the morphology and mechanical properties of the active materials. This highlights the importance of a fundamental understanding of the calendering process of electrodes composed of powders with different properties for the development of high-performance LIBs, especially when aiming fast-charging capabilities within a limited cell volume.
As the electrode manufacturing process is often time consuming and inefficient, and the calendering process has the most significant effect on the electrode mechanics and microstructure, the primary objective of this work is the prediction of the compaction behavior of electrodes based on powder properties. Thus, the main mechanical stress during calendering, namely the compressive stress, is transferred to the powder level. By understanding the relationship between powder and electrode properties, it is possible to efficiently identify suitable active materials based on the powder characteristics. This would allow for significant time and cost savings in the development of fast-charging LIBs, as electrode properties could be predicted from the initial powder compaction properties without the need for extensive experimental testing. Since the focus within this work is on graphite based anodes, two different types of graphite powders were investigated for this study. First, the compaction behavior of these graphites were analyzed with a developed powder compaction method. In the next step, electrodes were fabricated using the two graphite powders, which were then calendered to the same density. The resulting microstructures, including tortuosity and particle orientation were characterized and correlated with the initial powder compaction properties and electrode mechanics. The results reveal a relationship between the powder compaction properties and the microstructure, as well as the mechanics of the electrode.