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238 results on '"Domi, Yasuhiro"'

26. Electrochemical Lithiation and Delithiation Properties of FeSi2/Si Composite Electrodes in Ionic-Liquid Electrolytes

Author

Domi, Yasuhiro, Usui, Hiroyuki, Shindo, Yoshiko, Yodoya, Shuhei, Sato, Hironori, Nishikawa, Kei, and Sakaguchi, Hiroki

Subjects
Technology, Physical and theoretical chemistry, QD450-801, lithium-ion battery, composite, ionic-liquid electrolyte, negative electrode
Abstract

We investigated the applicability of ionic-liquid electrolytes to FeSi2/Si composite electrode for lithium-ion batteries. In conventional organic-liquid electrolytes, a discharge capacity of the electrode rapidly faded. In contrast, the electrode exhibited a superior cycle life with a reversible capacity of 1000 mA h g(Si)−1 over 850 cycles in a certain ionic-liquid electrolyte. The difference in the cycle life was explained by surface film properties. In addition, the rate performance of the FeSi2/Si electrode improved in another ionic-liquid electrolyte. Remarkably, lithiation of only Si in FeSi2/Si composite electrode occurred whereas each FeSi2- and Si-alone electrode alloyed with Li in the ionic-liquid electrolyte. FeSi2 certainly covered the shortcomings of Si and the FeSi2/Si composite electrode exhibited improved cycle life and rate capability compared to Si-alone electrode.

Published
2020

35. Fe–Nb Co-Doped Rutile TiO2for Anode Materials of Li-Ion Batteries

Author

Usui, Hiroyuki, Domi, Yasuhiro, Nguyen, Thi Hay, Sadamori, Yuma, Tanaka, Toshiyuki, and Sakaguchi, Hiroki

Abstract

We attempted to improve electrochemical performances of a rutile TiO2electrode as a Li-ion battery anode by doping with two kinds of elements with different ionic sizes. When Nb5+and Fe3+were doped into TiO2, the total doping amount could be increased up to 11 at.% because the doping amounts of Nb5+(9 at.%) and Fe3+(2 at.%) could exceed their solubility limits. It is considered that the compressive strain caused by the doping of larger Nb5+than Ti4+could be partially offset by the tensile strain induced by the doping of smaller Fe3+. The Fe–Nb-doped TiO2anode exhibited an excellent cycle performance and a good high-rate performance. We consider that these performances are attributed to the lattice parameter expansion and the electronic conductivity enhancement based on the increasing doping amount.

Published
2023
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40. Silicon-Based Nanocomposite Anodes with Excellent Cycle Life for Lithium-Ion Batteries Achieved by the Synergistic Effect of Two Silicides

Author

Domi, Yasuhiro, Usui, Hiroyuki, Okasaka, Takumi, Nishikawa, Kei, and Sakaguchi, Hiroki

Abstract

Nanocomposite electrodes comprising LaSi2and Si exhibit satisfactory charge–discharge cycling performances but their capacity is degraded after repeated cycles. A metallographic structure, in which the Si phase was finely dispersed in the LaSi2matrix phase, was formed before cycling. The elastic LaSi2relieved Si-generated stress and suppressed electrode disintegration. Contrarily, the LaSi2phase in the metallographic structure was surrounded by the Si matrix phase after cycling. The positional relationship between the two phases was reversed, and LaSi2could not relieve the stress. For a nanocomposite electrode containing CrSi2, which exhibits stiffness to withstand the Si-generated stress, the structural changes were suppressed after cycling, resulting in good cycling stability. Here, we considered that the addition of stiff silicides as a third phase to the LaSi2/Si composite could improve the cycle life. Thus, this study prepared nanocomposite electrodes containing elastic LaSi2, stiff MSi2(where M= Cr, Mo, Nb, Ta, Ti, or W), and elemental Si and investigated their electrochemical performances. Reaction behaviors, such as the metallographic structure, electrode thickness, and phase transition, were also clarified. The LaSi2/NbSi2/Si electrode exhibited the best cycle life without changes in its metallographic structure owing to the synergistic effect of stiff and elastic silicides.

Published
2024
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41. Potassiation and Depotassioation Properties of Sn4P3 Electrode in an Ionic-Liquid Electrolyte

Author

Domi, Yasuhiro, Usui, Hiroyuki, Nakabayashi, Eisuke, Yamamoto, Takayuki, Nohira, Toshiyuki, and Sakaguchi, Hiroki

Subjects
Negative Electrode, Sn4P3, K-ion Battery, Ionic-liquid Electrolyte
Abstract

K-ion battery is a potential candidate as a next-generation battery with a high energy density, long cycle life, and high safety. To commercialize the battery, the improvement of safety is absolutely essential. We apply a nonflammable ionic-liquid electrolyte to a Sn4P3 electrode as negative-electrode for K-ion battery. The electrode achieves the excellent cycling performance with a discharge capacity of 365 mA h g−1 over 100 cycles in the ionic-liquid electrolyte. Rate capability in the ionic-liquid electrolyte is almost the same as that in the organic-liquid electrolyte.

Published
2019

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