Investigating the influence of the calendering process on the 3D microstructure of single-layer and two-layer cathodes in lithium-ion batteries using synchrotron tomography

Further improvement of the performance of lithium-ion batteries is a central goal in state-of-the-art battery research to satisfy the permanently growing demands. This can be achieved by optimizing the 3D microstructure of the electrodes, which in turn depends on the material composition used as well as on the corresponding production parameters. Since the calendering process of electrodes has a significant impact on their microstructure, the goal of this paper is to further deepen the understanding of how varying the compaction load changes the microstructure of lithium-ion battery cathodes. For this purpose, three different sample sets are analyzed and compared to each other, using image data gained by synchrotron tomography. More precisely, we consider differently compacted thin and thick cathodes as well as a set of porosity-graded two-layer cathode samples. A phase-based as well as a particle-based segmentation of the tomographic image data is performed to allow for an extensive morphological analysis of the cathode samples, where, among others, mean geodesic tortuosity of the pore space and particle connectivity are considered to quantify changes of the 3D microstructure. Furthermore, for the two-layer sample set, a special focus is put on microstructural changes of both layers and the interface between them. • 3D microstructure analysis of differently compacted lithium-ion battery cathodes. • Phase-based and particle-based segmentation of tomographic image data. • Thin, thick and two-layer electrodes are quantitatively compared. • Negative effects of higher compaction loads are more pronounced for thick samples. • Two layer coating preferable compared to a single thick layer.