Anode microstructures from high-energy and high-power lithium-ion cylindrical cells obtained by X-ray nano-tomography

Graphite negative electrodes from a high-power and a high-energy cylindrical lithium-ion cell are reconstructed using X-ray nano-tomography. Large volumes and high resolution are required for an in-depth comparison of the design aspects for high-power and high-energy anode. Hence, quite big volumes of 2.37·106 μm3 and 1.27·106 μm3 have to be analyzed to cover the entire thickness of both anode layers. High resolutions of 273 nm and 233 nm voxel size are chosen for assessing volume specific graphite surface area, among other parameters, precisely. A hysteresis segmentation method is adapted for segmentation, featuring a symmetrical growing of both graphite and pore phase. Surface areas are calculated using the marching cube algorithm, particle sizes are calculated based on the Euclidean distance transform (EDT) and tortuosity values are calculated by solving the transport equation using a finite volume scheme in MATLAB. Analysis of these parameters leads to the assumption, that the electrolyte transport is limited by the pore structure of the high-energy graphite anode.