Develop energy materials
Sustainable society and electric vehicles are facilitated by battery technology; improving battery capacity is one of the social urgent issues today. Transition metal oxide materials are currently used for cathodes of lithium-ion batteries and magnesium rechargeable batteries, facing the intrinsic capacity limit determined by valence change of constituent transition metals. To tackle this problem, I study on strain effect yielded by a nano-domain microstructure in the oxide electrodes, which is expected to unlock large capacity delivered by anionic (e.g., oxygen and sulfur) reduction/oxidation (redox) reaction as well as the conventional cationic reaction.
Unveil subtle difference in “colors” of atoms
“Colors” of an atom in an X-ray region tell us a chemical state of the atom, which is one of the most important clues to understand the origin of materials properties. I have studied on resonant X-ray diffraction spectroscopy, which is a so-called coupling of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS and also called as XAFS). This technique enables to reveal valence states and local structure of an element at each crystallographic site and phase. I developed a fast measurement technique of diffraction anomalous fine structure (DAFS) and a direct analysis using the logarithmic dispersion relation. This technique was applied to a battery material for the first time, which revealed a degradation mechanism of the first charge/discharge cycle of lithium-ion batteries.
Image material surface and inside
An electrochemical reaction proceeds surface of a material while it also drastically changes inside of the material. Understanding both of them are of great importance to design the material. I developed a direct analysis technique for crystal truncation rod (CTR) analysis, which is so sensitive to the surface that even a single layer change on the surface can be detected. I am also working with Bragg coherent diffraction imaging (BCDI) of an electrode material.