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

We investigated the lithium peroxide (Li2O2) and pore size distribution in lithium–O2 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 Li2O2 in Li–O2 battery cathode electrodes. We verified by wave-propagation simulation that this approach efficiently improves the contrast of images in comparison with pure absorption. The Li2O2 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 Li2O2 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 Li2O2 and other byproducts.