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525 results on '"Sakuda, Atsushi"'

215. Morphological Effect on Reaction Distribution Influenced by Binder Materials in Composite Electrodes for Sheet-type All-Solid-State Lithium-Ion Batteries with the Sulfide-based Solid Electrolyte

Author

Chen, Kezheng, primary, Shinjo, Sae, additional, Sakuda, Atsushi, additional, Yamamoto, Kentaro, additional, Uchiyama, Tomoki, additional, Kuratani, Kentaro, additional, Takeuchi, Tomonari, additional, Orikasa, Yuki, additional, Hayashi, Akitoshi, additional, Tatsumisago, Masahiro, additional, Kimura, Yuta, additional, Nakamura, Takashi, additional, Amezawa, Koji, additional, and Uchimoto, Yoshiharu, additional

Published
2019
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224. Mechanochemical Synthesis, Structure, and Ionic Conductivity of K2NaYCl6and KNa2YCl6

Author

Ben Yahia, Hamdi, Motohashi, Kota, Ishibashi, Hiroki, Kubota, Yoshiki, Kosuga, Atsuko, Sakuda, Atsushi, and Hayashi, Akitoshi

Abstract

K2NaYCl6and KNa2YCl6were prepared by a mechanochemical synthesis route from NaCl, KCl, and YCl3as starting materials. The crystal structures and properties were characterized by X-ray powder diffraction, thermogravimetric and differential thermal analyses, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. At room temperature, both samples are isostructural to P21/c-Ba2LaRuO6. At high temperature (T< 500 °C), only K2NaYCl6exhibits a phase transition from the room-temperature form, which crystallizes in the monoclinic system, space group P21/c(No. 14) with a= 7.2447(4) Å, b= 7.5518(4) Å, c= 12.6454(8) Å, β = 124.557(3)°, V= 569.76(6) Å3, and Z= 2 to the high-temperature form, which crystallizes in the cubic system, space group Fm3̅m(No. 225) with a= 10.6903(1) Å, V= 1221.72(1) Å3, and Z= 4. The HT-K2NaYCl6(cF40) polymorph is isostructural to K2NaAlF6. The structures are monoclinic and cubic double perovskites A2BB′X6in which the octahedrally coordinated Na and Y atoms are well-ordered at the B and B′ sites, respectively. The A site is occupied by K and K/Na atoms in K2NaYCl6and KNa2YCl6, respectively. The P21/c⇄ Fm3̅mphase transition mechanism was accurately determined and is illustrated in a video. K2NaYCl6and KNa2YCl6exhibit ionic conductivities of 8 × 10–8and 4.9 × 10–9S cm–1at 75 °C, respectively.

Published
2024
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225. Aqueous solution synthesis of Na3SbS4–Na2WS4 superionic conductors.

Author

Yubuchi, So, Ito, Akane, Masuzawa, Naoki, Sakuda, Atsushi, Hayashi, Akitoshi, and Tatsumisago, Masahiro

Abstract

We report a route for the synthesis of Na3SbS4–Na2WS4 superionic conductors from aqueous solution. Na3SbS4–Na2WS4 has the highest high sodium-ion conductivity (4.28 mS cm−1 at 25 °C) of reported sulfide-based solid electrolytes prepared via liquid-phase methods. The antimony in Na3SbS4 is replaced by tungsten in a higher valence state, which is charge-compensated by sodium vacancies in the form Na3−xSb1−xWxS4. Introducing sodium vacancies while maintaining the 3D conduction pathways increases the pre-exponential factor in the Arrhenius plots of ionic conduction. The development of a facile synthetic protocol, as well as the high ionic conductivity and excellent chemical stability of Na3SbS4–Na2WS4 in the presence of water, is a major step towards the realization of all-solid-state sodium batteries. [ABSTRACT FROM AUTHOR]

Published
2020
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240. Visualizing Local Electrical Properties of Composite Electrodes in Sulfide All-Solid-State Batteries by Scanning Probe Microscopy

Author

Otoyama, Misae, Yamaoka, Takehiro, Ito, Hiroyuki, Inagi, Yuki, Sakuda, Atsushi, Tatsumisago, Masahiro, and Hayashi, Akitoshi

Abstract

Studies on local conduction paths in composite electrodes are essential to the realization of high-performance sulfide all-solid-state lithium batteries. Here, we directly evaluate the electrical properties of individual LiNi1/3Mn1/3Co1/3O2(NMC) electrode active material particles in composite positive electrodes by scanning probe microscopy (SPM) techniques. Kelvin probe force microscopy (KPFM) and scanning spreading resistance microscopy (SSRM) are combined. The results indicate that all NMC particles exhibit a charged state with increasing potential, but low electronic conduction paths exist at point of contacts of some NMC particles. Furthermore, the I–Vcharacteristics measured by conductive atomic force microscopy (C-AFM) suggest that these specific NMC particles show low charge–discharge reactivity. The results of the SPM techniques indicate that poor conduction locally limits the charge–discharge reactivity of electrode active materials, leading to the degradation of battery performance. Such an SPM combination accelerates the morphological optimization of composite electrodes by facilitating the investigation of the intrinsic electrical properties of the electrodes.

Published
2021
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241. Lubrication Tests to Support Optimal Performance Design Guidelines for Thrust Slide-Bearings in Scroll Compressors

Author

Ishii, Noriaki, Nonoguchi, Eiji, Anami, Keiko, Sakuda, Atsushi, Terada, Yuya, Imai, Yusuke, Sawai, Kiyoshi, and Knisely, Charles William

Subjects
Thrust Slide-Bearing, Optimization, Dsign Guideline, Scroll Compressor, Friction Power Loss
Abstract

This study focuses on the role of lubrication in the optimal performance design guidelines for the thrust slide-bearings in scroll compressors. The theoretical analysis of Ishii et al. showed that the minimum friction power loss in the thrust slide-bearing occurs at a certain outer radius of the friction surface. In the theoretical development, the physical thrust slide-bearing was modeled as a cylindrical thrust plate, representing the orbiting scroll, and the flat plate, representing the fixed scroll, with the same friction area as the physical bearing. The outer radius of the friction surface was varied for a fixed inner radius, where the fluid wedge angle between the sliding surfaces, due to axial loading on the thrust plate, was assumed to be constant at a small value. The average Reynolds equation by Patier & Cheng and the solid contact theory by Greenwood & Williamson were applied to calculate the resultant lubrication performance and finally the friction power loss at the sliding surface. The model showed that the friction power loss drastically decreases and then gradually increases, with increasing outer radius of the sliding surface.  The minimum value of friction power loss was about 80% lower than that of the conventional design thrust slide-bering. In order to confirm experimentally this predicted optimal lubrication performance, a thrust slide-bearing cylindrical-model submerged in a refrigerant oil SUNISO-RB68A was operated under pressurized conditions using R410A as the pressurizing gas. The pressure difference across the friction surface of the thrust bearing was fixed at 0.6 MPa, corresponding to the rated operation condition of a small cooling capacity scroll compressor. In the experiments, a special device was fabricated to maintain a constant fluid wedge angle between the friction surfaces due to the net pressure-induced elastic deformation of the thrust plate. The friction power loss at the friction surface was measured over a wide range of orbiting speeds from 1200 rpm up to 6000 rpm for a fixed orbiting radius of 3.0 mm. The resulting measured data exhibited showed the predicted tendency that the lubrication of the thrust slide-bearing is substabtially by increasing the outer radius. The friction power loss decreased with increasing outer-to-inner radii ratio of friction surface. The minimum loss occurred at an outer-to-inner radii ratio of about 2.1 for an operating speed of 3600 rpm, a significant 80% reduction relative to the usual conventional design ratio.

Published
2016

242. First-Principles Calculation Study of Na+Superionic Conduction Mechanism in W- and Mo-Doped Na3SbS4Solid Electrolytes

Author

Jalem, Randy, Hayashi, Akitoshi, Tsuji, Fumika, Sakuda, Atsushi, and Tateyama, Yoshitaka

Abstract

The guiding principle for the design of inorganic compounds with high ionic conductivity has been extensively sought to realize next-generation all-solid-state batteries (ASSBs). Recently, a sulfide-type Na+ion conductor, cubic Na3SbS4with W doping (Na2.88Sb0.88W0.12S4), was reported with unprecedentedly high ionic conductivity of 3.2 × 10–2S cm–1, making it now a champion solid electrolyte for Na-ASSB (A. Hayashi et al., Nat. Commun. 2019, 10, 5266). Herein, density functional theory molecular dynamics (DFT-MD) calculations were performed for pristine, W-doped, and Mo-doped Na3SbS4to examine the ionic conduction mechanism (Boltzmann factor vs prefactor) and the aliovalent cation dopant effects in Na3SbS4. We showed that Na vacancies induced by cation doping play crucial roles in superionic conductivity, while the diffusion process is rather characterized by the concerted motion of Na+ions. A comparison between the two dopants, Mo6+and W6+, revealed that the conductivity enhancement can be primarily explained by a decrease of Na+ion activation energy, which is found to be strongly correlated to the enlargement of Na Wyckoff site cages brought upon by the smaller WS4/MoS4tetrahedral volume relative to the host SbS4volume. This descriptor of the pathway free volume can suggest a general guiding principle for superionic conduction that can be applied to other cations, in addition to explaining the superior performance of W-doped Na3SbS4.

Published
2020
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243. Amorphous Metal Polysulfides: Electrode Materials with Unique Insertion/Extraction Reactions

Author

Sakuda, Atsushi, primary, Ohara, Koji, additional, Fukuda, Katsutoshi, additional, Nakanishi, Koji, additional, Kawaguchi, Tomoya, additional, Arai, Hajime, additional, Uchimoto, Yoshiharu, additional, Ohta, Toshiaki, additional, Matsubara, Eiichiro, additional, Ogumi, Zempachi, additional, Okumura, Toyoki, additional, Kobayashi, Hironori, additional, Kageyama, Hiroyuki, additional, Shikano, Masahiro, additional, Sakaebe, Hikari, additional, and Takeuchi, Tomonari, additional

Published
2017
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247. Electrochemistry

Author

TATSUMISAGO, Masahiro, primary, SAKUDA, Atsushi, additional, and HAYASHI, Akitoshi, additional

Published
2017
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