X‐Ray Tomography of Porous, Transition Metal Oxide Based Lithium Ion Battery Electrodes

We report the use of synchrotron radiation X-ray tomographic microscopy (SRXTM) to obtain statistically significant volume (~ 700 × 700 × 70 µm³) 3D reconstructions of porous electrode microstructures of transition metal oxide based electrodes. We implement a segmentation algorithm that allows identification of individual particles and validate it by showing that the calculated particle size distribution (PSD) is in agreement with experimentally determined PSD obtained with laser diffraction. We study the microstructure of LiNi_1/3Mn_1/3Co_1/3O₂ (NMC)-based cathodes, prepared with varying weight percent of carbon black and binder (2-5 wt%) and different compressions (0-2000 bar), and their electrochemical performance. Tomographic data (raw and processed with particles identified and labeled) and the corresponding electrochemical data for 16 different cathodes is provided open source. The microstructure datasets can be used to study electrode properties like porosity, tortuosity, electrode anisotropy, and homogeneity, or as realistic geometries for three dimensional (3D) electrochemical simulations. The electrochemical data is intended to aid in the verification of simulation models. The large number of studied particles (approx. 7000-19000 per electrode) allows us to investigate spatially resolved PSD and shows that the vicinity of electrode boundaries is populated by smaller particles than the bulk electrode. In addition to insight into electrode morphology, we demonstrate that the technique is capable of resolving features on the sub-particle level such as particle fracture, which is observed here under high compression conditions.