X-ray Nanocomputed Tomography in Zernike Phase Contrast for Studying 3D Morphology of Li–O₂ Battery Electrode

Abstract

We investigated the lithium peroxide (Li 2 O 2 ) and pore size distribution in lithium−O 2 battery electrodes at different states of charge using transmission X-ray microscopy coupled with Zernike phase contrast to carry out nanocomputed tomography. We report that such a technique enables us, at the nanoscale, to distinguish light elements such as carbon and Li 2 O 2 in Li− O 2 battery cathode electrodes. We verified by wave-propagation simulation that this approach efficiently improves the contrast of images in comparison with pure absorption. The Li 2 O 2 distribution and thickness, interphases, and pore network are visualized and quantified, giving a valuable insight into our cathode architecture. From this 3D analysis, we highlight modifications of the air-cathode morphology and the Li 2 O 2 spatial organization as well as their potential implication in terms of carbon surface passivation and pore-clogging. After the full recharge process, this technique can also reveal the spatial distribution of the residual Li 2 O 2 and other byproducts.

The electrode tortuosity factor: why the conventional tortuosity factor is not well suited for quantifying transport in porous Li-ion battery electrodes and what to use instead

“…Porosity can be measured either directly, using 3D imaging techniques [7][8][9] , indirectly, using techniques such as helium pycnometry, or inferred from knowledge of the electrode precursors along with the mass and dimensions of the finished electrode. Surface area can, in principle, be explored using imaging techniques, although resolution constraints can present a challenge and adsorption techniques like the Brunauer-Emmett-Teller (BET) method are typically preferred.…”

“…The interfacial double layer capacitance per unit microstructural electrode active surface area is chosen from refs 9,16 .…”

3D Quantification of Microstructural Properties of LiNi0.5Mn0.3Co0.2O2 High‐Energy Density Electrodes by X‐Ray Holographic Nano‐Tomography

“…Focused ion beam/scanning electron microscopy (FIB/SEM), [ 28–30 ] and transmission X‐ray computed tomography (TXM CT) including µCT and nanoCT [ 18,27,31–35 ] are the most commonly used 3D techniques to study microstructure of batteries. The FIB/SEM technique usually offers a higher spatial resolution (≈10 nm pixel size) compared to TXM CT, but only a small volume (≈10 × 10 × 10 µm 3 ) can be acquired under reasonable time and labor.…”

“…used the Zernike phase contrast to capture the morphology of the Li 2 O 2 in a Li‐air electrode. [ 34 ] Moreover, the workflow is quite similar to the absorption‐based technique, which enables a straightforward approach to obtain the 3D microstructure data.…”

Probing and Interpreting the Porosity and Tortuosity Evolution of Li-O2 Cathodes on Discharge through a Combined Experimental and Theoretical Approach

“…The in-line Zernike phase contrast technique involving a phase ring in the back focal plane of the zone plate was used to increase the contrast between carbon and lithium peroxide. 45 Measurements were performed at 8 keV with a monochromatic beam (Δ E / E = 10 –4 ). The distance sample to detector of 3329 mm provided an X-ray magnification of 46.…”