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760 results on '"Matsubara, Eiichiro"'

58. Structural Variation in Carbonate Electrolytes by the Addition of Li Salts Studied by X‐Ray Total Scattering

Author

Kimura, Koji, primary, Hayashi, Kouichi, additional, Kiuchi, Hisao, additional, Morita, Masahito, additional, Haruyama, Jun, additional, Otani, Minoru, additional, Sakaebe, Hikari, additional, Fujisaki, Fumika, additional, Mori, Kazuhiro, additional, Yonemura, Masao, additional, Takabayashi, Yasuhiro, additional, Nakatani, Tomotaka, additional, Fujinami, So, additional, Fukunaga, Toshiharu, additional, and Matsubara, Eiichiro, additional

Published
2020
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66. Direct observation of layered-to-spinel phase transformation in Li2MnO3 and the spinel structure stabilised after the activation process

Author

Shimoda, Keiji, Oishi, Masatsugu, Matsunaga, Toshiyuki, Murakami, Miwa, Yamanaka, Keisuke, Arai, Hajime, Ukyo, Yoshio, Uchimoto, Yoshiharu, Ohta, Toshiaki, Matsubara, Eiichiro, and Ogumi, Zempachi

Abstract

Li2MnO3 is an important parent component in lithium- and manganese-rich layered oxides (LMRs), which are one of the promising positive electrode materials for next-generation lithium ion rechargeable batteries. Here, we report the layered-to-spinel phase transformation in Li2MnO3 during the initial charging process to characterise its unique delithiation behaviour, which gives an insight into the relationship between the structure, superior capacities and degradation of LMR electrodes. The atomic-scale observation using scanning transmission electron microscopy (STEM) techniques suggests that the structural transformation occurs in a biphasic manner within a single particle. The formed phase has a Li-defect spinel structure, indicating that the delithiation leads to Mn migration from the transition-metal layer to the Li layer, accompanied by some oxygen release. This layered-to-spinel phase transformation is an essential bulk process in the initial activation of Li2MnO3. During the lithiation in the 1st discharge, the Mn remigration occurs and the layered structure is again formed with significant disordering. During the multiple cycles, the defect spinel structure is stabilised and becomes more oxygen-deficient with a lower Mn valency. As a consequence, the amount of inserted Li decreases, which corresponds to the capacity and voltage fading observed in Li2MnO3 and LMRs.

Published
2017

96. Optimum compositions for the low-temperature fabrication of highly ordered FePt (001) and FePt (110) films

Author

Seki, Takeshi, Shima, Toshiyuki, Takanashi, Koki, Takahashi, Yukio, Matsubara, Eiichiro, and Hono, Kazuhiro

Subjects
Thin films -- Research, Dielectric films -- Research, Electromagnetism -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The composition dependence of the degree of chemical order S and uniaxial magnetic anisotropy energy [K.sub.u] has been investigated for FePt (001) and FePt (110) films deposited at the substrate temperature [T.sub.s] = 300[degrees]C, and the optimum compositional region for L[1.sub.o] ordering in FePt (110) films has been compared with that in FePt (001) films. It has been found that high S and large [K.sub.u] are obtained around the stoichiometric composition for FePt (110) films, whereas they are obtained around an off-stoichiometric Pt-rich composition for FePt (001) films, indicating that the difference in optimum compositions for achieving highly ordered structure between FePt (001) and FePt (110) films at reduced temperature. Index Terms--Composition dependence, FePt thin film, low-temperature fabrication, sputter-deposition.

Published
2004

97. Effective Bulk Activation and Interphase Stabilization of Silicon Negative Electrode by Lithium Pre-Doping for Next-Generation Batteries

Author

50818557, Saito, Morihiro, Kato, Kiyomi, Ishii, Shunya, Yoshii, Kazuki, Shikano, Masahiro, Sakaebe, Hikari, Kiuchi, Hisao, Fukunaga, Toshiharu, Matsubara, Eiichiro, 50818557, Saito, Morihiro, Kato, Kiyomi, Ishii, Shunya, Yoshii, Kazuki, Shikano, Masahiro, Sakaebe, Hikari, Kiuchi, Hisao, Fukunaga, Toshiharu, and Matsubara, Eiichiro

Abstract

To clarify the effects of Li pre-doping of a Si negative electrode for potential application in next-generation energy storage systems, such as Li–S and Li–O2 batteries, such electrodes were prepared by direct Li pre-doping using Li metal foil and by electrochemical pre-doping at 700 mA g−1 (Si) using a two-electrode cell. These were evaluated by comparing their charge/discharge properties, mainly by half-cell operation at a limited capacity of 2000 mAh g−1 (Si). Fluoroethylene carbonate (FEC) was added to form a stable solid electrolyte interphase film on the surface of the electrodes. The depth and homogeneity of Li pre-doping were improved by using the direct Li pre-doping method and by FEC addition, respectively. The rapid Li pre-doping of this method caused cracks and pulverization of the Si nanoparticles and promoted deep Li alloying by decreasing the Li+ diffusion distance. The tough homogeneous solid electrolyte interphase film derived from FEC suppressed electrolyte decomposition and enabled a fast Li alloying/de-alloying reaction. Addition of 10 mass% FEC to the half-cell electrolyte repaired damage to the interphase film caused by the large volume change of Si nanoparticles and improved cyclability to exceed 230 cycles.

Published
2019

98. Structural characterization of an amorphous VS₄ and its lithiation/delithiation behavior studied by solid-state NMR spectroscopy

Author

60467727, 60455269, Shimoda, Keiji, Koganei, Kazuto, Takeuchi, Tomonari, Matsunaga, Toshiyuki, Murakami, Miwa, Sakaebe, Hikari, Kobayashi, Hironori, Matsubara, Eiichiro, 60467727, 60455269, Shimoda, Keiji, Koganei, Kazuto, Takeuchi, Tomonari, Matsunaga, Toshiyuki, Murakami, Miwa, Sakaebe, Hikari, Kobayashi, Hironori, and Matsubara, Eiichiro

Abstract

Vanadium sulfide (VS₄) is one of the promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of its high theoretical capacity (1196 mA h g⁻¹). Crystalline VS₄ has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c axis are loosely connected to each other through van der Waals interactions. In this study, an amorphous VS₄ is prepared by mechanical milling of the crystalline material, and its lithiation/delithiation behavior is investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy. The amorphous VS₄ shows a chain structure similar to that of crystalline VS₄. The amorphous host structure is found to change drastically during the lithiation process to form Li₃VS₄: the V ions become tetrahedrally coordinated by S ions, in which the valence states of V and S ions simultaneously change from V⁴⁺ to V⁵⁺ and S⁻ to S²⁻, respectively. When the Li insertion proceeds further, the valence state of V ions is reduced. After the 1[st] cycle, the amorphous VS₄ recovers to the chain-like structure although it is highly disordered. No conversion to elemental V is observed, and a high capacity of 700 mA h g⁻¹ is reversibly delivered between 1.5 and 2.6 V.

Published
2019

100. Reaction Mechanism of Li2MnO3Electrodes in an All-Solid-State Thin-Film Battery Analyzed by Operando Hard X-ray Photoelectron Spectroscopy

Author

Hikima, Kazuhiro, Shimizu, Keisuke, Kiuchi, Hisao, Hinuma, Yoyo, Suzuki, Kota, Hirayama, Masaaki, Matsubara, Eiichiro, and Kanno, Ryoji

Abstract

Li2MnO3is a promising cathode candidate for Li-ion batteries because of its high discharge capacity; however, its reaction mechanism during cycling has not been sufficiently explicated. Observations of Mn and O binding energy shifts in operando hard X-ray photoelectron spectroscopy measurements enabled us to determine the charge-compensation mechanism of Li2MnO3. The O 1speak splits at an early stage during the first charge, and the concentration of lower-valence O changes reversibly with cycling, indicating the formation of a low-valence O species that intrinsically participates in the redox reaction. The O 1speak-splitting behavior, which indicates the number of valences of O in Li2MnO3, is supported by the computational results for an O3 to O1 structural transition. This is in agreement with the results of our previous study, wherein we confirmed this O3 to O1 transition based on in situsurface X-ray diffraction analysis, X-ray photoelectron spectroscopy, and first-principles formation energy calculations.

Published
2022
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