In the present demonstration, the powerful characterization tool, synchrotron X-ray phase contrast tomography imaging technique will be employed to characterize the evolution of Li electrodes during cycling. To this end, we have designed and fabricated a tomography cell (tomo-cell) for the three-dimensional nondestructive investigation, as shown in Fig. 1, along with a schematic illustration of the beamline set-up.
Fig. 1. a) Photograph of the fabricated proof-of-concept cell. b) Corresponding schematic representation of the cell consisting of a polyamide-imide housing (brown), two screw electrodes and retaining screws each on top (light grey), two sealing rings (yellow), a porous separator (white) sandwiched between two electrodes (blue and green). c) Schematic representation of the experimental setup of the tomography station at the BAMline at BESSY II, Helmholtz-Zentrum Berlin, Germany. This figure has been adapted from ACS Energy Lett., 2017, 2, pp 94–104, with permission by the American Chemical Society.
Selected results of our previous investigations using this tomo-cell about the evolution of Li electrodes in half-cells (lithium-silicon, lithium-sulfur and lithium-lithium cobalt oxide) and symmetrical cells (Li-Li) will be briefly demonstrated. The morphological evolution of Li electrodes based on these measurements will also be summarized. These unprecedented findings, which were not accessible from conventional microscopic characterizations and electrochemical measurements, fundamentally deepen our understanding of the evolution mechanism of Li electrodes during battery cycling. The insights obtained could open up the way toward design principles and opportunities to accelerate the commercialization of Li metal.