Hi. I, Tomoya Kawaguchi, Ph.D. is a materials scientist and assistant professor of Institute for Materials Research, Tohoku University in Japan.
See Career for more detail.
My research interests are developing oxide materials for rechargeable batteries such as lithium-ion batteries and magnesium rechargeable batteries based on a concept of nanodomain microstructure.
See Research for more detail.
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.
Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in situ Bragg coherent diffraction imaging Journal Article Forthcoming
Physical Review Letters, Forthcoming.
Journal of the Korean Physical Society, 75 (7), pp. 528-533, 2019.
High Anionic Conductive Form of PbxSn2–xF4 Journal Article
Chemistry of Materials, 31 (18), pp. 7704-7710, 2019.
Phycal Review Letters, 122 , pp. 017202, 2019.
Phys. Chem. Chem. Phys., 21 , pp. 23749-23757, 2019.
Structural Dynamics, 5 , pp. 064501, 2018.
Scientific Reports, 8 (1), pp. 15086, 2018, ISBN: 4159801833518.
J. Phys. Chem. C, 122 (35), pp. 20099-20107, 2018, ISSN: 1932-7447.
J. Phys. Chem. C, 122 (34), pp. 19298–19308, 2018, ISSN: 1932-7447.
Solid State Ionics, 323 , pp. 32–36, 2018, ISSN: 01672738.
J. Appl. Crystallogr., 51 , pp. 1–6, 2018.
Solid State Ionics, 320 (September 2017), pp. 387–391, 2018, ISSN: 01672738.
Layering and Ordering in Electrochemical Double Layers Journal Article
J. Phys. Chem. Lett., 9 , pp. 1265–1271, 2018, ISSN: 1948-7185.
Continue reading “Publication”
Generally, optics based on the electromagnetics is described with the refractive index, while such index does not barely appear in X-ray diffraction (XRD) from the kinematical approach, presumably because of the different historical background; however, it is of great importance to see their relationship to understand the diffraction anomalous fine structure (DAFS) method.
The atomic form factor is a Fourier transform of the electron distribution in an atom; therefore, it is a real number and independent of photon energy. In contrast, there exists an absorption edge and a fine structure in an absorption spectrum in the x-ray region. Thus, the absorption term should be included into the scattering length as an imaginary part, which is proportional to the absorption cross-section, by assuming a more elaborated model rather than that of a cloud of free electrons.
A structure factor is calculated by summing up scattering factors of each atom with multiplying the phases at each atomic position in a unit cell. It is a facile approach to calculate the structure factor; however, the calculation becomes complicated when the unit cell includes the large number of atoms. Thus, the calculation of the structure factor should be carried out based on the crystallographic site in space group, which is more versatile and convenient.
Institute for Materials Research, Tohoku University, Japan, 2018-
Structure-Controlled Functional Materials Laboratory (prof. Tetsu Ichitsubo)
Materials Science Division, Argonne National Laboratory, U.S.A., 2017-2019
Synchrotron Studies of Materials Group (supervisor: Hoydoo You)
JSPS overseas research fellow
Japan Society for Promotion of Science (JSPS), Japan, 2017-2019
Research assistant professor
Technical Director (Synchrotron Radiation Study Group) of RISING and RISING2 projects
Office of Society Academia Collaboration for Innovation, Kyoto University, Japan, 2015-2017
JSPS research fellow (DC2), JSPS, Japan, 2013 – 2015
- Ph.D., Materials Science, Kyoto University, Kyoto, Japan, 2015
- M.S., Material Science, Kyoto University, Kyoto, Japan, 2012
- B.S., Engineering Science, Kyoto University, Kyoto, Japan, 2010
- Science and Mathematics Course, Otemae High School, Osaka, Japan, 2006
- TOEIC score: 925/990 as of 2019
Awards and Honors
- Encouraging award, the Japanese Society for Synchrotron Radiation Research (JSSRR), 2016
- Best student presentation award, annual meeting of JSSRR, 2015
- Best student presentation award, annual meeting of JSSRR, 2014
- Best student presentation award, annual meeting of JSSRR, 2013
Argonne National Laboratory
Structural analysis of the electrochemical double layer using crystal truncation rod (CTR) analysis. Direct determination of the surface structure from CTR. Bragg coherent diffraction imaging of the internal composition of the alloy catalysis particles, Materials Science Division, Argonne National Laboratory, 2017 – 2019
Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aobaku, Sendai 980-8577, Japan
Structure-Controlled Functional Materials Laboratory