Microstructural X-Ray Tomographic Analysis of Commercial Lib Electrodes

Systematic characterization, understanding, and improvement of Lithium Ion Battery (LIB) electrodes at the micro- and nanometer scales is essential to improving LIB capacity, safety and lifetime. The visualization and quantification of LIB electrode microstructures using X-ray tomographic microscopy (XTM) of ex-situ electrode samples [1-4] and using in-operando setups [5] has proved highly valuable for electrode micro-structure understanding and optimization.

Here we present the XTM structural analysis of different commercial carbon based anode LIB electrodes. Electrode samples have been scanned in absorption contrast mode at the TOMCAT beamline of the Swiss Light Source at Paul Scherrer Intitute in Switzerland resulting in voxel edge length of 0.33 micrometer. The segmented XTM data sets were analyzed for the distributions of porosity, tortuosity, effective relative diffusivity, and pore space constrictions.

The cross sections of four different commercial anodes are shown in Figure a) and display distinct microstructures. As shown in the histograms in Figure b), these differences can be quantified by assessing the spread in through-plane (perpendicular to current collector) and in-plane (parallel to current collector) tortuosities calculated for multiple 1050 μm²regions throughout the cell. Such analysis of the electrode microstructure is linked to the corresponding rate capability that is determined using half-cell based three-dimensional electrochemical modeling [6]. Furthermore, because electrodes typically fail at localized weak points, special focus is put on quantifying constrictions in the pore structure and understanding their potential impact on electrochemical performance and cell life.

References

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