Preparation and Characterization of Li-Ion Graphite Anodes Using Synchrotron Tomography

Abstract

We present an approach for multi-layer preparation to perform microstructure analysis of a Li-ion cell anode active material using synchrotron tomography. All necessary steps, from the disassembly of differently-housed cells (pouch and cylindrical), via selection of interesting layer regions, to the separation of the graphite-compound and current collector, are described in detail. The proposed stacking method improves the efficiency of synchrotron tomography by measuring up to ten layers in parallel, without the loss of image resolution nor quality, resulting in a maximization of acquired data. Additionally, we perform an analysis of the obtained 3D volumes by calculating microstructural characteristics, like porosity, tortuosity and specific surface area. Due to a large amount of measurable layers within one stacked sample, differences between aged and pristine material (e.g., significant differences in tortuosity and specific surface area, while porosity remains constant), as well as the homogeneity of the material within one cell could be recognized.

A New Method for Quantitative Marking of Deposited Lithium by Chemical Treatment on Graphite Anodes in Lithium‐Ion Cells

“…The XRPD patterns of the uncycled and pristine anode show one dominant peak indicating 2H-graphite (Figure 3a). Additional minor peaks representing Li 2 CO 3 are present in the powder pattern of the plated sample A1.H ence, the film on the surface can therefore be identifieda sL i 2 CO 3 .C ompared to previous work, [9,11] we want to point out the safe chemicalt reatment with IPAt ov isualize lithium deposition performed on large automotive lithiumi on cells andt he precise verification of Li 2 CO 3 by XRPD (denoted by arrow). This is the first time known to the authors that deposited metallic lithium on graphitea nodesf rom large automotive cells can be conserved with the original frozen shape.…”

“…Given this situation, here we report an ew method for qualitative and quantitative marking of deposited metallicl ithium in large lithium-ion cellsb yc hemical treatment with IPAt o obtain zabuyelite (Li 2 CO 3 ), which can be observed by high-resolution X-ray powder diffraction (XRPD). Anode samples were cycled and extracted as described [9] from HEV (hybrid electric vehicle) cylindrical (A1)a nd EV (electric vehicle) pouch cells (A2), separated, washed with DMC, IPA, and dried at 25 8Ci n air (Figure 1a). On the same spots of deposited lithium on the surfaceo ft he anode the white coating of Li 2 CO 3 was obtained after 10 min through oxidation of C 3 H 7 O-Li/OH-Li and CO 2 from air (Figure 1b and 1c).Initially,t he compositiono ft he white coating of A1 (58.78 %) and A2 (56.83 %) was investigated with canning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) (1.3 mm 1.6 mm, Figure 2).…”

Stochastic 3D modeling of the microstructure of lithium-ion battery anodes via Gaussian random fields on the sphere

“…The cell was disassembled and four samples were extracted from different positions and layers in the cell. This was done to ensure that the samples were as reflective as possible of the material's structure; see [23]. The obtained image data is shown in Fig.…”

“…Details on the measurement and on the sample preparation method that was used to minimize the differences in the samples induced by varying measurement conditions are described in [23]. After imaging and reconstruction, the sample data is in the form of four 3D images, each 2097 Â 828 Â 119 voxels.…”

“…A limitation of these simulation based approaches, however, is that it is very difficult to obtain realistic 3D microstructure models to use as input. This is because the small scales make 3D imaging of sufficiently large and representative material samples very difficult; see [21][22][23][24][25]. In addition, it would be desirable to investigate realistic microstructures that do not correspond to materials that have already been physically produced [26].…”