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Your search keyword '"Sakuda, Atsushi"' showing total 540 results
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540 results on '"Sakuda, Atsushi"'

1. Unusual nanoscale coexistence of polar-nonpolar domains underlying oxygen storage properties in Ho(Mn, Ti)O$_{3+\delta}$

Author

Nakajima, Hiroshi, Uchihashi, Kento, Tsukasaki, Hirofumi, Morikawa, Daisuke, Tanaka, Hiroyuki, Furukawa, Tomohiro, Kurushima, Kosuke, Yamasaki, Jun, Ishibashi, Hiroki, Kubota, Yoshiki, Sakuda, Atsushi, Hayashi, Akitoshi, and Mori, Shigeo

Subjects
Condensed Matter - Materials Science
Abstract

Hexagonal manganese oxides RMnO$_3$ show intriguing topological ferroelectric-domain walls with variable conductivity, leading to domain wall engineering. Despite the numerous experimental studies on the polar nanoscale structures, controlling ferroelectric domains has not been sufficiently investigated. Here, we reveal the unprecedented coexistence of polar-nonpolar nanoscale domains that can be formed by substituting Ti ions in HoMnO$_3$. Unusual polar nanoscale domains are embedded in nonpolar domains with different crystallographic symmetry. This polar-nonpolar coexisting structure is naturally assembled by adjusting the lattice length during a solid-state reaction process. Furthermore, the comprehensive study reveals that the reversible microstructural change with a nonpolar-polar transition is strongly correlated with the oxygen storage properties in Ho(Mn, Ti)O$_{3+\delta}$. The present results provide important insight into the nanoscale polar-nonpolar domain coexistence in functional rare-earth manganese oxides, RMnO$_3$.

Published
2023
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8. Crystallization behaviors in superionic conductor Na$_3$PS$_4$

Author

Nakajima, Hiroshi, Tsukasaki, Hirofumi, Ding, Jiong, Kimura, Takuya, Nakano, Takumi, Nasu, Akira, Hirata, Akihiko, Sakuda, Atsushi, Hayashi, Akitoshi, and Mori, Shigeo

Subjects
Condensed Matter - Materials Science
Abstract

All-solid-state batteries using sodium are promising candidates for next-generation rechargeable batteries due to the limited lithium resources. A practical sodium battery requires an electrolyte with high conductivity. Cubic Na$_3$PS$_4$ exhibiting high conductivity of over 10$^{-4}$ S cm$^{-1}$ is obtained by crystallizing amorphous Na$_3$PS$_4$ synthesized by ball milling. Amorphous Na$_3$PS$_4$ crystallizes in a cubic structure and then is transformed into a tetragonal phase upon heating. In this study, in situ observation by transmission electron microscopy demonstrates that the crystallite size drastically increases during the transition from the cubic phase to the tetragonal phase. Moreover, an electron diffraction analysis reveals that amorphous domains and nano-sized crystallites coexist in the cubic Na$_3$PS$_4$ specimen, while the tetragonal phase contains micro-sized crystallites. The nano-sized crystallites and the composite formed by crystallites and amorphous domains are most likely responsible for the increase in conductivity in the cubic Na$_3$PS$_4$ specimens.

Published
2021
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26. Aqueous solution synthesis of lithium-ion conductive tin-based sulphide electrolytes.

Author

Kimura, Takuya, Tanigaki, Hayata, Sakuda, Atsushi, Tatsumisago, Masahiro, and Hayashi, Akitoshi

Subjects
SOLID electrolytes, IONIC conductivity, AQUEOUS solutions, HUMAN ecology, ORGANIC solvents, SUPERIONIC conductors
Abstract

To overcome the challenges associated with the toxicity of the majority of organic solvents for the liquid phase synthesis of solid electrolytes toward the human body and environment, we demonstrate the synthesis of tin-based sulphide electrolytes using water, which is the most environmentally friendly solvent. ortho-Thiostannate, i.e., Li4SnS4, was obtained from a mixture of Li2S, Sn, and S using aqueous solution synthesis. Furthermore, Li10SnP2S12, a superionic conductor, was obtained by mixing an aqueous solution of Li4SnS4 and tetrahydrofuran suspension of Li3PS4, which exhibited the highest ionic conductivity (5.9 × 10−3 S cm−1 at 25 °C) in liquid-phase synthesis. This study successfully demonstrates that water can be efficiently used to synthesize sulphide electrolytes instead of conventional organic solvents. [ABSTRACT FROM AUTHOR]

Published
2024
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38. Dynamic Volume Change of Li2S-Based Active Material and the Influence of Stacking Pressure on Capacity in All-Solid-State Batteries

Author

Fujita, Yushi, Münch, Konrad, Asakura, Taichi, Motohashi, Kota, Sakuda, Atsushi, Janek, Jürgen, and Hayashi, Akitoshi

Abstract

All-solid-state batteries are considered as a reasonable further development of conventional lithium-ion batteries. While the same active materials may be used, solid electrolytes may offer higher safety than liquid electrolytes and enable the reversible operation of the lithium metal anode. Also, solid-state lithium/sulfur (Li/S) batteries are being investigated due to their high theoretical specific energy. Li2S-based composite positive electrodes have been demonstrated to achieve their theoretical capacity, high rate performance, and good cycling stability under high stacking pressures. However, during charging, Li2S is converted to sulfur and shrinks by 45%, and the resulting loss of contact between the composite particles leads to mechanical degradation during cycling. To better understand the correlation between the charge–discharge capacities and stack pressure during cycling in high-capacity Li2S-based active materials, the dynamic volume change of the positive electrode layer is measured. The volume change of the Li2S-based composite positive electrode is observed by using in situ scanning electron microscopy. Furthermore, by using Li4Ti5O12, which is well-known to undergo almost no volume change during cycling, as the counter electrode, charge–discharge capacities were found to depend on the initial volume change of the composite positive electrode. Finally, candidates for the negative electrode in full-cell applications of all-solid-state Li/S batteries are discussed. This study represents a major step toward mitigating mechanical deterioration in all-solid-state Li/S batteries stemming from the volumetric expansion and contraction of sulfur-active materials.

Published
2024
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42. Lithium Ion Transport Environment by Molecular Vibrations in Ion‐Conducting Glasses.

Author

Yamada, Hiroki, Ohara, Koji, Hiroi, Satoshi, Sakuda, Atsushi, Ikeda, Kazutaka, Ohkubo, Takahiro, Nakada, Kengo, Tsukasaki, Hirofumi, Nakajima, Hiroshi, Temleitner, Laszlo, Pusztai, Laszlo, Ariga, Shunsuke, Matsuo, Aoto, Ding, Jiong, Nakano, Takumi, Kimura, Takuya, Kobayashi, Ryo, Usuki, Takeshi, Tahara, Shuta, and Amezawa, Koji

Subjects
MOLECULAR vibration, LITHIUM ions, MONTE Carlo method, SOLID electrolytes, EDUCATIONAL mobility
Abstract

Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all‐solid‐state batteries, a promising technology for electric vehicles. In this context, Li3PS4 glass, a promising solid electrolyte candidate, exhibits dynamic coupling between the Li+ cation mobility and the PS43− anion libration, which is commonly referred to as the paddlewheel effect. In addition, it exhibits a concerted cation diffusion effect (i.e., a cation–cation interaction), which is regarded as the essence of high Li ion transport. However, the correlation between the Li+ ions within the glass structure can only be vaguely determined, due to the limited experimental information that can be obtained. Here, this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds. It is found that three types of Li ions are present in Li3PS4 glass, and that the more mobile Li ions (i.e., the Li3‐type ions) exhibit a characteristic correlation at relatively long distances of 4.0–5.0 Å. Furthermore, reverse Monte Carlo simulations combined with deep learning potentials that reproduce X‐ray, neutron, and electron diffraction pair distribution functions showed an increase in the number of Li3‐type ions for partially crystallized glass structures with improved Li ion transport properties. Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences. Thus, considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes. [ABSTRACT FROM AUTHOR]

Published
2024
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