Abstract:
Compton-scattered X-ray spectra correspond to the electron momentum density in matter and reflect the wave function in the ground state [1]. Therefore, it is relatively easy to interpret the observed Compton-scattered X-ray spectrum by ab initio electronic structure calculations. The observed information is bulk-sensitive because prover X-rays have energies above 100 keV and are highly penetrating through materials.
This research focuses on lithium-ion secondary battery materials. In green technologies such as electric vehicles, improvement of rechargeable battery materials is a key to enhance energy density and charge-discharge stability. In practical batteries, it is important to understand redox reactions and their spatial distribution. From a view point of redox reactions, we measured spinel LixMn2O4, a Li-ion battery cathode material. We found that the redox orbital in the lithium insertion and extraction process is mainly the oxygen 2p orbital [2], although the redox orbital has been considered to be manganese 3d states [3,4]. Furthermore, analysis of the shape of Compton-scattered X-ray spectra can be used as a new nondestructive testing (NDT) technique. We proposed S-parameter analysis to observe the spatial distribution of redox reactions in commercial batteries [5].
Our research shows that Compton scattering measurements can provide insight into the mechanism of lithium batteries and point the way to improved battery materials and new battery designs.
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