Microstructural Analysis of Lithium-Ion Battery Cathodes Using Tomography Methods - Possibilities and Limitations

Abstract

A deep knowledge of the 3D microstructure is essential for optimizing performance in Lithium ion battery electrodes. Tomography methods like focused ion beam-secondary electron microscopy (FIB-SEM) and X-ray tomography are the most frequently used 3D characterization techniques for battery electrodes. While each method has advantages and disadvantages, understanding the complex morphology of electrodes requires a complementary, multi-scale 3D approach.In this work, the possibilities and limitations for both 3D techniques, X-ray and FIB-SEM tomography, are studied using the example of a LiNiCoAlO2-LiCoO2 blend cathode from a commercial cell. The same cathode sample was analyzed with both techniques and moreover with different devices to enable a comparison of the obtained data quality. The material fractions, porosity, surface area and tortuosity are calculated from the different data sets and the results are compared with special emphasis on the differentiation of the different active materials and the carbon-binder phase. The reliable determination of these parameters is essential because they are needed, for example, to compare different electrode structures or to study the influence of the microstructure on the electrode performance to optimize the electrode structure. Figure 1