Toward new frontiers : Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams

Program D01-4	Visualization of valence and electronic states using elemental analisys with muonic X-ray
Principal Investigator	UMEGAKI, Izumi (Toyota Central R&D Labs., Inc.)

In this study, by clarifying the relationship between the atomic muon capture process and the intensity of muonic X-rays, we aim to establish an analysis method to distinguish various valences of an atom in addition to identification of elements. Through discussions with theorists in the B02 group, we will deepen our theoretical understanding of the effect on the structure of muonic X-ray by atomic muon capture process. After that, we will realize imaging technology that visualizes the valence and state of the atom, by both the imaging technology of the element analysis that the B01 group is working on and the improvement of muon beam (especially the miniaturization of the beam) by the C02 group. Then, we will achieve a three-dimensional imaging of the distribution of Li inside Li-ion battery to detect Li metal deposition on electrode.

For high capacity and reliablity improvement of Li-ion batteries, it is desired that the battery reaction occurs uniformly throughout an electrode and that the distribution of Li is uniform in the electrode. When ununiformity of the distribution of Li is significant, heat generation or short circuit may occur as a problem of Li-ion batteries. In general, the information electrochemically obtained from the electrode is the average information of the electrode. To investigate the distribution of Li in the electrode, one should destroy the battery and analyze using small pieces of the electrode. If we succeed to observe the distribution of Li in a non-destructive manner, it will be possible to investigate the change over time of the Li distribution and to discover a factor causing decrement in performance. We believe that this technique promotes the development for the improvement of the performance and relibility of Li-ion batteries.

Inside a Li-ion battery, corresponding to the movement folio ions, a valence of a transition metal changes so as to compensate the charge in the electrode. By observing the valence, it is also possible to indirectly know the distribution of Li. In addition, new batteries with Na, F, Mg etc. instead of Li are currently being studied. Even in these new batteries, uniformity of distribution of carrier ions is important. Elemental analysis with muonic X-ray can also be a key tool to study these new batteries since there is no element that cannot be detected by this technique.

We believe that elemental analysis with muonic X-ray has a high potential to be a powerful non-destructive analysis technique. In this research, we will add a function of observing chemical states such as valences and electronic states to this non-destructive three-dimensional imaging technique. The key to realize this is a further understanding of the atomic muon capture process. In order to achieve it, we will collaborate with the theoretical research group B02 based on experimental results.

Members

Reference Materials

• I. Umegaki et al., “Detection of Li in Li-ion battery electrode materials by muonic X-ray,” JPS Conf. Proc. 21, 011041-5 (2018).