YAMAMOTO Kentaro

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Profile and Settings

• Name (Japanese)

  Yamamoto

• Name (Kana)

  Kentaro

Research Interests

• 固体イオニクス
• 無機材料
• 二次電池
• 電気化学

Research Areas

• Nanotechnology/Materials, Structural and functional materials
• Nanotechnology/Materials, Energy chemistry
• Nanotechnology/Materials, Inorganic compounds/materials chemistry

Research Experience

• Jul. 2021, Mar. 2022, 京都大学大学院 人間・環境学研究科, 特定准教授
• Apr. 2016, Jun. 2021, 京都大学大学院, 人間・環境学研究科, 特定助教
• Apr. 2015, Mar. 2016, Kyushu University, 稲盛フロンティア研究センター, 特任助教

Association Memberships

• THE CARBON SOCIETY OF JAPAN
• 日本ポーラログラフ学会
• 固体イオニクス学会
• THE ELECTROCHEMICAL SOCIETY OF JAPAN
• 電池技術委員会

Ⅱ．研究活動実績

Published Papers

• Refereed, Applied Physics Letters, AIP Publishing, Partial cation disorder in Li₂MnO₃ obtained by high-pressure synthesis, Aierxiding Abulikemu; Shenghan Gao; Toshiyuki Matsunaga; Hiroshi Takatsu; Cédric Tassel; Hiroshi Kageyama; Takashi Saito; Toshiki Watanabe; Tomoki Uchiyama; Kentaro Yamamoto; Yoshiharu Uchimoto; Tsuyoshi Takami, While atomic disorder has provided a paradigm shift in crystalline materials because of unusual atomic arrangements and functional response, “partial” disorder is scarcely reported until now. We discovered partial cation disorder in Li₂MnO₃ with fewer stacking faults, which was synthesized under high pressure. Mn and Li atoms in a Mn_2/3Li_1/3O₂ layer disorder while Li atoms in a Li layer order. Magnetization and specific heat measurements indicate a long-range antiferromagnetic (AF) order below 35 K. The irreversibility observed in the magnetization data and the hump observed for the specific heat data suggest the coexistence of an AF order and a partial magnetic disorder. Neutron diffraction measurements reveal that the coexisted state is formed instead of the Néel AF state that has previously been reported for conventional Li₂MnO₃. These results indicate that high pressure makes a breakthrough to introduce partial disorder within crystals and designs not only a unique magnetic structure but also other physical properties., 02 May 2022, 120, 18, 182404, 182404, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), State of the Active Site in La_1–xSr_xCoO_3−δ Under Oxygen Evolution Reaction Investigated by Total-Reflection Fluorescence X-Ray Absorption Spectroscopy, Yadan Ren; Jun Oyama; Tomoki Uchiyama; Yuki Orikasa; Toshiki Watanabe; Kentaro Yamamoto; Tsuyoshi Takami; Yoshinori Nishiki; Shigenori Mitsushima; Yoshiharu Uchimoto, Recent developments in hydrogen energy devices have furthered the research on sustainable hydrogen production methods. Among these, the water splitting process has been considered a promising hydrogen production method, particularly, in alkaline media. The lack of information on the reaction active sites under the conditions of the oxygen evolution reaction (OER) hinders establishing guidelines for catalyst development. In the case of powder catalysts, many operando techniques also measure bulk information, and therefore, extracting information on the reaction active sites is challenging. Accordingly, film electrodes were used in this study, and the electrochemical performance and reaction kinetics of perovskite-type La1-xSrxCoO3-δ films as OER catalysts synthesized by pulsed laser deposition were investigated. By combining ex situ X-ray absorption spectroscopy (XAS) and operando total-reflection fluorescence X-ray absorption spectroscopy (TRF-XAS), we succeeded in observing a significant oxidation state change on the surface of La0.6Sr0.4CoO3-δ, which indicated that the active surface sites were formed upon applying the OER potential. This surface reconstruction resulted in numerous active sites at the reaction interface, thereby enhancing the OER activity. This study provides definitive evidence for the surface reconstruction of OER catalysts, which enhances the fundamental understanding of OER catalyst behaviors, and can inspire the design of active OER catalysts by suitable surface modulation., 25 Apr. 2022, 5, 4, 4108, 4116, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Studies on the inhibition of lithium dendrite formation in sulfide solid electrolytes doped with LiX (X = Br, I), Seunghoon Yang; Masakuni Takahashi; Kentaro Yamamoto; Koji Ohara; Toshiki Watanabe; Tomoki Uchiyama; Tsuyoshi Takami; Atsushi Sakuda; Akitoshi Hayashi; Masahiro Tatsumisago; Yoshiharu Uchimoto, A promising method to increase the energy density of all-solid-state batteries (ASSBs) featuring lithium ions as carriers is to employ Li metal as the anode. However, this has been accompanied by safety problems like flammable accidents associated with lithium dendrites originating from reactions with the solid electrolyte, leading to reduced battery performance. To overcome this issue toward the commercialization of ASSBs, various approaches have been proposed by many researchers. Among the suggested solutions, the use of lithium-halide-doped Li3PS4, to suppress lithium dendrite formation, has attracted attention. LiI-doped Li3PS4 has shown the highest lithium dendrite growth suppression among lithium-halide-doped systems, but the reason for this is unclear. Thus, we attempted to clarify the cause of this suppression by comparing LiBr-doped Li3PS4 with LiI-doped Li3PS4. Investigation using various methods such as electrochemical evaluation, X-ray absorption spectroscopy, X-ray computed tomography, and pair distribution function analysis revealed that two factors affect the suppression of Li dendrite growth: the suppression of the current density distribution by improving the ionic conductivity and the stable interfacial layer. This is the main reason LiI-doped Li3PS4 shows excellent Li dendrite suppression., Apr. 2022, 377, 115869, 115869, Scientific journal

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• Refereed, Chemical Physics Reviews, AIP Publishing, Multiscale and hierarchical reaction mechanism in a lithium-ion battery, Yuki Orikasa; Kentaro Yamamoto; Takeshi Shimizu; Yoshiharu Uchimoto, Mar. 2022, 3, 1, 011305, 011305, Scientific journal

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• Refereed, Chemistry of Materials, American Chemical Society (ACS), Anion Substitution at Apical Sites of Ruddlesden–Popper-type Cathodes toward High Power Density for All-Solid-State Fluoride-Ion Batteries, Yanchang Wang; Kentaro Yamamoto; Yoshihiro Tsujimoto; Toshiyuki Matsunaga; Datong Zhang; Zulai Cao; Koji Nakanishi; Tomoki Uchiyama; Toshiki Watanabe; Tsuyoshi Takami; Hidenori Miki; Hideki Iba; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, All-solid-state fluoride-ion batteries (FIBs) that use fluoride ions as carrier ions offer a new horizon for next-generation energy storage devices owing to their high specific capacities. Materials that utilize topochemical insertion and desorption reactions of fluoride ions have been proposed as cathodes for FIBs; among them, Ruddlesden-Popper-type perovskite-related compounds are promising cathode materials owing to reversible fluoride-ion (de)intercalations with low volume expansion compared to conversion-type cathode materials. Although it is essential to improve the power density of the compounds for practical application, the relationship between the structure and power density is still not clearly understood. In this study, we synthesized chemically fluorinated Ruddlesden-Popper compounds, LaSrMnO4 and apical-site-substituted oxyfluoride Sr2MnO3F, and examined the correlations between their structures and electrochemical properties; Sr2MnO3F showed better power density. Open-circuit voltage measurements, X-ray absorption spectroscopy, and synchrotron X-ray diffraction revealed that electrochemical F- insertion into LaSrMnO4 proceeds via a two-phase reaction with relatively high volume expansion, whereas that into Sr2MnO3F proceeds via a solid-solution reaction with relatively low volume expansion. The substitution of oxygen in the apical sites with fluorine suppressed phase transitions with large volume changes, resulting in improved power density., 05 Jan. 2022, 34, 2, 609, 616, Scientific journal

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• Refereed, Condensed Matter, MDPI AG, Magnetic Compton Scattering Study of Li-Rich Battery Materials, Kosuke Suzuki; Yuji Otsuka; Kazushi Hoshi; Hiroshi Sakurai; Naruki Tsuji; Kentaro Yamamoto; Naoaki Yabuuchi; Hasnain Hafiz; Yuki Orikasa; Yoshiharu Uchimoto; Yoshiharu Sakurai; Venkatasubramanian Viswanathan; Arun Bansil; Bernardo Barbiellini, The redox process in a lithium-ion battery occurs when a conduction electron from the lithium anode is transferred to the redox orbital of the cathode. Understanding the nature of orbitals involved in anionic as well as cationic redox reactions is important for improving the capacity and energy density of Li-ion batteries. In this connection, we have obtained magnetic Compton profiles (MCPs) from the Li-rich cation-disordered rock-salt compound LixTi0.4Mn0.4O2 (LTMO). The MCPs, which involved the scattering of circularly polarized hard X-rays, are given by the momentum density of all the unpaired spins in the material. The net magnetic moment in the ground state can be extracted from the area under the MCP, along with a SQUID measurement. Our analysis gives insight into the role of Mn 3d magnetic electrons and O 2p holes in the magnetic redox properties of LTMO., 28 Dec. 2021, 7, 1, 4, 4, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), High Rate Capability from a Graphite Anode through Surface Modification with Lithium Iodide for All-Solid-State Batteries, Seunghoon Yang; Kentaro Yamamoto; Xiaohan Mei; Atsushi Sakuda; Tomoki Uchiyama; Toshiki Watanabe; Tsuyoshi Takami; Akitoshi Hayashi; Masahiro Tatsumisago; Yoshiharu Uchimoto, All-solid-state batteries (ASSBs) have been attracting attention as a potential paradigm for batteries in the future, as they are safer because they do not leak and are stable at high temperatures compared to lithium-ion batteries (LIBs) that use liquid electrolytes; further, the use of a bipolar structure is expected to improve energy density. For ASSBs, graphite is one of the most promising practical anode materials because of its superior power density in LIBs. However, the power density of ASSBs is unsatisfactory for practical applications and is lower than that of LIBs. One reason for this is the slow lithium ion transport at the interface between the graphite anode and solid electrolyte (SE). Because of the low redox potential for lithium ion intercalation into graphite (close to the lithium reduction potential), sulfide SEs undergo reductive decomposition, which impedes lithium ion transport at the interface with graphite. To address this problem, we attempted to coat LiI, which is stable at the lithium deposition potential, directly onto the graphite surface and examined the effect on the sulfide SE and electrochemical performance. The electrochemical measurements showed that the graphite composite without LiI showed a discharge capacity of 248 mA h g-1, while that with 5 wt % LiI showed a relatively high discharge capacity of approximately 348 mA h g-1. Impedance spectroscopy and S and P K-edge X-ray absorption spectroscopy indicated that the LiI-coated graphite composites displayed a stable interface behavior, in contrast to the uncoated graphite composite, after the lithiation process., 19 Dec. 2021, 5, 1, 667, 673, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Accelerated lithium ions diffusion at the interface between LiFePO4 electrode and electrolyte by surface-nitride treatment, Kentaro Yamamoto; Takahiro Yoshinari; Akihide Kuwabara; Eri Kato; Yuki Orikasa; Koji Nakanishi; Tomoki Uchiyama; Kazuhiko Maeda; Hiroshi Kageyama; Toshiaki Ohta; Yoshiharu Uchimoto, Improving the rate performance of lithium-ion batteries is important for the widespread utilization of electric vehicles and energy grids. Because the rate-determining step for cathode materials with a two-phase reaction is nucleation reaction at the material surface, surface modification is a promising approach for achieving this goal. However, the cause of this improvement in the reaction rate at the interface between the surface-modified cathode and the electrolyte is not clearly understood. In this study, we prepared a surface-nitrided LiFePO4 thin film and investigated its electrochemical properties. In addition, we examined its surface structure using surface-sensitive X-ray absorption spectroscopy measurements and first-principles calculations, and discussed the correlation between the rate performance and the interfacial reaction. The experiments revealed the formation of a new energy level and the increase of the Fe[sbnd]O bond distance at the surface of LiFePO4 due to nitrogen doping. The electronic and local structural changes accelerated lithium ion diffusion at the interface between surface-nitrided LiFePO4 and the electrolyte, improving the rate performance., Dec. 2021, 373, 115792, 115792, Scientific journal

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• Refereed, Nature Communications, Springer Science and Business Media LLC, Hydride-based antiperovskites with soft anionic sublattices as fast alkali ionic conductors, Shenghan Gao; Thibault Broux; Susumu Fujii; Cédric Tassel; Kentaro Yamamoto; Yao Xiao; Itaru Oikawa; Hitoshi Takamura; Hiroki Ubukata; Yuki Watanabe; Kotaro Fujii; Masatomo Yashima; Akihide Kuwabara; Yoshiharu Uchimoto; Hiroshi Kageyama, Most solid-state materials are composed of p-block anions, only in recent years the introduction of hydride anions (1s²) in oxides (e.g., SrVO₂H, BaTi(O,H)₃) has allowed the discovery of various interesting properties. Here we exploit the large polarizability of hydride anions (H^–) together with chalcogenide (Ch^2–) anions to construct a family of antiperovskites with soft anionic sublattices. The M₃HCh antiperovskites (M = Li, Na) adopt the ideal cubic structure except orthorhombic Na₃HS, despite the large variation in sizes of M and Ch. This unconventional robustness of cubic phase mainly originates from the large size-flexibility of the H^– anion. Theoretical and experimental studies reveal low migration barriers for Li⁺/Na⁺ transport and high ionic conductivity, possibly promoted by a soft phonon mode associated with the rotational motion of HM₆ octahedra in their cubic forms. Aliovalent substitution to create vacancies has further enhanced ionic conductivities of this series of antiperovskites, resulting in Na_2.9H(Se_0.9I_0.1) achieving a high conductivity of ~1 × 10^–4 S/cm (100 °C)., Dec. 2021, 12, 1, Scientific journal

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• Refereed, ChemElectroChem, Wiley, Quadruple perovskite oxides CaMn7O12 proceed by two‐active‐site reaction mechanism for oxygen evolution reaction, Yadan Ren; Kodai Kashihara; Tomoki Uchiyama; Yuki Orikasa; Toshiki Watanabe; Kentaro Yamamoto; Tsuyoshi Takami; Toshiyuki Matsunaga; Yoshinori Nishiki; Shigenori Mitsushima; Yoshiharu Uchimoto, The oxygen evolution reaction (OER) is one of the essential energy conversion reactions for hydrogen production. In quadruple perovskite oxides AA’3B4O12 (A=Ca, Sr, A’=Cu, Mn and B=3d metals), the new reaction mechanism of O−O bond formation between adsorbed oxygen species at adjacent A’-B sites has been proposed in recent studies. This idea of multiple transition metals working together to form an active site, rather than a single active site, is appealing, but has not been systematically investigated so far. This study examined catalytic OER performances of CaMn7O12 quadruple perovskite oxides with precisely controlled Mn(A′)−Mn(B) distance by doping with Sr, Cu and Al. The crystal structure and the state of cations and O were investigated through XRD with Rietveld refinement and X-ray absorption spectroscopy. The OER catalytic activity is clearly correlated with the distance of Mn(A’)−Mn(B) while both eg state of Mn and O 2p band center unchanged. The shrinkage of the A’-B distance affects the stability of O−O bond on A’-B site and accelerates OER kinetics., 29 Oct. 2021, 8, 23, 4605, 4611, Scientific journal

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• Refereed, Advanced Energy Materials, Wiley, Reversible and Fast (De)fluorination of High‐Capacity Cu2O Cathode: One Step Toward Practically Applicable All‐Solid‐State Fluoride‐Ion Battery, Datong Zhang; Kentaro Yamamoto; Yanchang Wang; Shenghan Gao; Tomoki Uchiyama; Toshiki Watanabe; Tsuyoshi Takami; Toshiyuki Matsunaga; Koji Nakanishi; Hidenori Miki; Hideki Iba; Koji Amezawa; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, 17 Oct. 2021, 11, 45, 2102285, 2102285, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Quantitative Evaluation of the Activity of Low-Spin Tetravalent Nickel Ion Sites for the Oxygen Evolution Reaction, Yadan Ren; Tomoya Horiguchi; Tomoki Uchiyama; Yuki Orikasa; Toshiki Watanabe; Kentaro Yamamoto; Tsuyoshi Takami; Toshiyuki Matsunaga; Yoshinori Nishiki; Shigenori Mitsushima; Yoshiharu Uchimoto, Oxide catalysts containing tetravalent nickel exhibit high oxygen-active catalytic activity. We investigated the effects of lithium content (x) on the electrocatalytic activity of LixNi0.5Mn1.5O4, a spinel that provides only divalent and tetravalent nickel ions in a KOH aqueous electrolyte for the oxygen evolution reaction (OER). The lithium content was controlled by the chemical delithiation of Li0.96Ni0.49Mn1.51O4 using NO2BF4. Upon employing this approach, nickel changed from the divalent to tetravalent state. The OER activity increased with decreasing x, and a higher activity than that of standard LaNiO3 was observed at x = 0.00. Comprehensive Tafel analyses and X-ray spectroscopic investigations revealed a downshift in the Ni conduction band, indicating that high OER activity correlated with strong hybridization of the Ni 3d and O 2p orbitals. These insights into the role of Ni4+ in high OER activity are expected to facilitate the development of other highly active Ni-based electrocatalysts., 26 Sep. 2021, 4, 10, 10731, 10738, Scientific journal

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• Refereed, ACS Applied Materials & Interfaces, American Chemical Society (ACS), Rate-Determining Process at Electrode/Electrolyte Interfaces for All-Solid-State Fluoride-Ion Batteries, Datong Zhang; Hiroyuki Nakano; Kentaro Yamamoto; Kenta Tanaka; Tatsuma Yahara; Kazuyuki Imai; Takuya Mori; Hidenori Miki; Shinji Nakanishi; Hideki Iba; Toshiki Watanabe; Tomoki Uchiyama; Koji Amezawa; Yoshiharu Uchimoto, 21 Jun. 2021, 13, 25, 30198, 30204, Scientific journal

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• Refereed, Chemistry of Materials, American Chemical Society (ACS), Investigation of the Suppression of Dendritic Lithium Growth with a Lithium-Iodide-Containing Solid Electrolyte, Masakuni Takahashi; Toshiki Watanabe; Kentaro Yamamoto; Koji Ohara; Atsushi Sakuda; Takuya Kimura; Seunghoon Yang; Koji Nakanishi; Tomoki Uchiyama; Masao Kimura; Akitoshi Hayashi; Masahiro Tatsumisago; Yoshiharu Uchimoto, All-solid-state lithium batteries that use lithium metal as the anode have extremely high energy densities. However, for lithium metal anodes to be used, lithium dendrite formation must be addressed. Recently, the addition of lithium iodide (LiI) to sulfide solid electrolytes was found to suppress lithium dendrite formation. It is unclear whether the cause of this suppression is the improvement of the ionic conductivity of the solid electrolyte itself or the electrochemical properties of the lithium metal/solid electrolyte interface. In this study, the cause of the suppression was quantitatively elucidated. The effect of the interphase on the dendrite growth of doping LiI into Li3PS4 was determined using X-ray absorption spectroscopy and X-ray computed tomography measurements. The results revealed that LiI-doped Li3PS4 suppressed the dendrite formation by maintaining the interface due to inhibition of the reductive decomposition of Li3PS4. In addition, annealed LiI-doped Li3PS4 showed a greater dendrite suppression ability as the ionic conductivity increased. From these results, we not only found that the physical properties of the lithium metal/solid electrolyte interface and the bulk ionic conductivity contribute to lithium dendrite suppression but also quantitatively determined the proportions of the contributions of these two factors., 15 Jun. 2021, 33, 13, 4907, 4914, Scientific journal

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• Refereed, Nature, Springer Science and Business Media LLC, Tomographic reconstruction of oxygen orbitals in lithium-rich battery materials, Hasnain Hafiz; Kosuke Suzuki; Bernardo Barbiellini; Naruki Tsuji; Naoaki Yabuuchi; Kentaro Yamamoto; Yuki Orikasa; Yoshiharu Uchimoto; Yoshiharu Sakurai; Hiroshi Sakurai; Arun Bansil; Venkatasubramanian Viswanathan, 10 Jun. 2021, 594, 7862, 213, 216, Scientific journal

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• Refereed, ACS Omega, American Chemical Society (ACS), Impact of the Composition of Alcohol/Water Dispersion on the Proton Transport and Morphology of Cast Perfluorinated Sulfonic Acid Ionomer Thin Films, Xiao Gao; Kentaro Yamamoto; Tomoyasu Hirai; Noboru Ohta; Tomoki Uchiyama; Toshiki Watanabe; Hideto Imai; Seiho Sugawara; Kazuhiko Shinohara; Yoshiharu Uchimoto, The dispersion of perfluorinated sulfonic acid ionomers in catalyst inks is an important factor that controls the performance of catalyst layers in membrane electrode assemblies of polymer electrolyte fuel cells. Herein, the effects of water/alcohol compositions on the morphological properties and proton transport are examined by grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and electrochemical impedance spectroscopy. The thin films cast by a high water/alcohol ratio Nafion dispersion have high proton conductivity and well-defined hydrophilic/hydrophobic phase separation, which indicates that the proton conductivity and morphology of the Nafion thin films are strongly influenced by the state of dispersion. This finding is expected to further understand the morphology and proton transport properties of Nafion thin films with different water/alcohol ratios, which has implications for the performance of the Pt/Nafion interface., 24 May 2021, 6, 22, 14130, 14137, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Cu–Pb Nanocomposite Cathode Material toward Room-Temperature Cycling for All-Solid-State Fluoride-Ion Batteries, Datong Zhang; Takahiro Yoshinari; Kentaro Yamamoto; Yuya Kitaguchi; Aika Ochi; Koji Nakanishi; Hidenori Miki; Shinji Nakanishi; Hideki Iba; Toshiki Watanabe; Tomoki Uchiyama; Yuki Orikasa; Koji Amezawa; Yoshiharu Uchimoto, 06 Apr. 2021, 4, 4, 3352, 3357, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Improvement of lithium ionic conductivity of Li3PS4 through suppression of crystallization using low-boiling-point solvent in liquid-phase synthesis, Masakuni Takahashi; Seunghoon Yang; Kentaro Yamamoto; Koji Ohara; Nguyen Huu Huy Phuc; Toshiki Watanabe; Tomoki Uchiyama; Atsushi Sakuda; Akitoshi Hayashi; Masahiro Tatsumisago; Hiroyuki Muto; Atsunori Matsuda; Yoshiharu Uchimoto, Liquid-phase synthesis for solid electrolytes has received considerable attention owing to its shape control, with the potential to produce particles easily on a large scale, and its low cost and energy consumption. However, solid electrolytes prepared through liquid-phase synthesis have been shown to have lower ionic conductivity than solid electrolytes prepared through the mechanical milling method. Recently, following various efforts, our group found that the crystallinity and remaining intermediate are the reasons for the low ionic conductivity of these materials. By using tetrahydrofuran (THF), we successfully improved the ionic conductivity of Li PS to 1.85 × 10 S cm at 25 °C, higher than that afforded by ethyl propionate, which was reported to produce the highest ionic conductivity among the solvents used for liquid-phase synthesis. High-energy X-ray diffraction (XRD) measurements coupled with pair distribution function (PDF) analysis were employed to analyze the synthesized materials in order to determine why the ionic conductivity was higher than that of a sample prepared using ethyl propionate. The PDF analysis revealed that the crystallization of Li PS can be suppressed using THF, which has a lower boiling point than ethyl propionate. Moreover, it was revealed that the solvent could not be removed completely when the material has an amorphous structure, and thus, the ionic conductivity was lower than that of a material prepared using the solid-phase synthesis method. 3 4 3 4 −4 −1, Mar. 2021, 361, 115568, 115568, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), High Ionic Conductivity of Liquid-Phase-Synthesized Li3PS4 Solid Electrolyte, Comparable to That Obtained via Ball Milling, Kentaro Yamamoto; Seunghoon Yang; Masakuni Takahashi; Koji Ohara; Tomoki Uchiyama; Toshiki Watanabe; Atsushi Sakuda; Akitoshi Hayashi; Masahiro Tatsumisago; Hiroyuki Muto; Atsunori Matsuda; Yoshiharu Uchimoto, Recently, several sulfide solid electrolytes have been synthesized by liquid-phase synthesis for the commercialization of all-solid-state batteries. Unfortunately, the ionic conductivity for most of these electrolytes is unsatisfactory compared to that of solid electrolytes synthesized by conventional ball milling. This problem is attributed to different mechanisms between the liquid phase and the solid phase in reaction and formation. However, to the best of our knowledge, the effect of the solvent on the ionic conductivity of solid electrolytes has not been extensively investigated, although the identification of these properties is a key point in understanding the liquid-phase synthesis. Herein, the correlation between ionic conductivity and crystallinity originating from the solvents used has been investigated. As a result, the ionic conductivity of the electrolyte was found to be strongly dependent on polarity (δP) with low crystallinity. The highest ionic conductivity (5.09 × 10-4 S cm-1 at 25 °C) was obtained using butyl acetate, which exhibited the lowest δP. Moreover, the highest ionic conductivity of Li3PS4 produced by liquid-phase synthesis using butyl acetate was very comparable to that obtained by ball milling (5.14 × 10-4 S cm-1)., 12 Feb. 2021, 4, 3, 2275, 2281, Scientific journal

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• Refereed, Journal of Alloys and Compounds, Elsevier BV, Rocksalt type Li2Nb0·15Mn0·85O3 without structure degradation or redox evolution upon cycling, Aierxiding Abulikemu; Toshiyuki Matsunaga; Aruto Watanabe; Kentaro Yamamoto; Tomoki Uchiyama; Koji Nakanishi; Shogo Kawaguchi; Keiichi Osaka; Yoshiharu Uchimoto, Voltage and capacity decay problems of Li MnO -based lithium rich layered cathode materials are still unsolved, which are the major barriers for its practical application. Intensive investigations of their mechanisms have been proceeded in recent years, which clarify cation ordered arrangement and spinel deterioration are culprits in structural aspect. Herein, we conduct various analyses to a rocksalt type Li Nb Mn O , whose first charge process is along with primary oxygen redox as Li MnO , but subsequently shows much better capacity retention. This material suffers from severe voltage decay and overpotential during the cycle but hard X-ray diffraction indicates it can remain rocksalt structure without any tendency of spinel deterioration or cation ordering even with massive lithium vacancies. XAS results further show there is no evident oxygen redox activity from the second cycle, while the redox range of Mn nearly has no change during the cycle. Our results demonstrate that disordered lithium rich cathode materials could be promising to exhibit highly reversible capacity upon long cycling, and their voltage decay problem could be easier to be solved for different mechanism from layered one. 2 3 2 0·15 0·85 3 2 3, Feb. 2021, 853, 156984, 156984, Scientific journal

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• Refereed, Chemistry of Materials, American Chemical Society (ACS), Phase Transition Behavior of MgMn2O4 Spinel Oxide Cathode during Magnesium Ion Insertion, Feilure Tuerxun; Saeko Otani; Kentaro Yamamoto; Toshiyuki Matsunaga; Hiroaki Imai; Toshihiko Mandai; Toshiki Watanabe; Tomoki Uchiyama; Kiyoshi Kanamura; Yoshiharu Uchimoto, The 3d transition metal oxides with a spinel structure are among the most promising cathode materials for magnesium batteries. In this study, we investigated the reaction mechanism of magnesium ion insertion for magnesium spinel oxides, MgMn2O4, by electrochemical measurements, X-ray absorption spectroscopy (XAS), and synchrotron X-ray diffraction (XRD) with Rietveld analysis. Open-circuit-potential and XAS measurements showed that Mg2+ insertion into MgMn2O4 does not proceed via a simple two-phase coexistence reaction between the spinel and rock-salt phases. Synchrotron XRD measurements showed that Mg2+ insertion into MgMn2O4 involves crystal structural changes in three stages. In the early stage of the Mg2+ insertion process (0 < x < 0.2), Mg2+ is inserted into the spinel (MgMn2O4) phase and rock-salt (Mg1.2Mn2O4) phases, which are included in the pristine samples, without significant volume changes. In the middle stage of the Mg2+ insertion process (0.2 < x < 0.4), Mg2+ is inserted into the Mg1+αMn2O4 spinel phase and the Mg2-βMn2O4 rock-salt phases with a large volume change. In the last stage of Mg2+ insertion process (0.4 < x < 0.56), Mg2+ insertion proceeds via a two-phase coexistence reaction between Mg1.4Mn2O4 spinel and Mg1.6Mn2O4 rock-salt phases without Mg content changes in either phase. The phase transition from the Mg1+αMn2O4 spinel phase to the Mg2-βMn2O4 rock-salt phase with a large volume change resulted in significant polarization during the Mg2+ insertion process. Suppressing the phase transition, accompanied by a large volume change, is important in designing a spinel oxide cathode with a high rate performance., 29 Jan. 2021, 33, 3, 1006, 1012, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Operando X-ray Absorption Spectroscopic Study on the Influence of Specific Adsorption of the Sulfo Group in the Perfluorosulfonic Acid Ionomer on the Oxygen Reduction Reaction Activity of the Pt/C Catalyst, Chen Liu; Tomoki Uchiyama; Noriyuki Nagata; Masazumi Arao; Kentaro Yamamoto; Toshiki Watanabe; Xiao Gao; Hideto Imai; Syota Katayama; Seiho Sugawara; Kazuhiko Shinohara; Koichiro Oshima; Shigeki Sakurai; Yoshiharu Uchimoto, The influence of specific adsorption of the sulfo group in the perfluorosulfonic acid ionomer, Nafion, on the oxygen reduction reaction (ORR) of a carbon-supported Pt/C catalyst using a thin-film rotating disk electrode was investigated. The relationship between the catalyst activity and coating of the Pt/C catalyst with Nafion was quantitatively evaluated through electrochemical measurements, operando X-ray absorption spectroscopy (XAS), and CO stripping voltammetry. Activity of the Pt/C catalyst decreased with increasing ionomer-to-carbon weight ratios. To date, the effect of specific adsorption on a catalyst has been investigated using CO stripping voltammetry. However, quantitative evaluation of specific adsorption at the ORR potential (0.50-1.0 V) has not been performed yet. We quantitatively evaluated the specific adsorption during the ORR by measuring the 5d orbital vacancy of the Pt/C catalyst using operando XAS. The difference in the electronic structures of Pt in the high potential range, with and without the ionomer, was successfully established., 21 Jan. 2021, 4, 2, 1143, 1149, Scientific journal

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• Refereed, Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), Kinetic Analysis and Alloy Designs for Metal/Metal Fluorides toward High Rate Capability for All-solid-state Fluoride Ion Batteries, Takahiro Yoshinari; Datong Zhang; Kentaro Yamamoto; Yuya Kitaguchi; Aika Ochi; Koji Nakanishi; Hidenori Miki; Shinji Nakanishi; Hideki Iba; Tomoki Uchiyama; Toshiki Watanabe; Toshiyuki Matsunaga; Koji Amezawa; Yoshiharu Uchimoto,

  New concepts for electrochemical energy storage devices are required to handle the physicochemical energy density limit that Li-ion batteries are approaching. All-solid-state fluoride-ion batteries (FIBs), in which monovalent fluoride anions...

  , 2021, 9, 11, 7018, 7024, Scientific journal

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• Refereed, Chemistry of Materials, American Chemical Society (ACS), Fluoride-Ion Shuttle Battery with High Volumetric Energy Density, Hiroyuki Nakano; Toshiyuki Matsunaga; Takuya Mori; Koji Nakanishi; Yoshiyuki Morita; Kazuto Ide; Ken-ichi Okazaki; Yuki Orikasa; Taketoshi Minato; Kentaro Yamamoto; Zempachi Ogumi; Yoshiharu Uchimoto, With the increasing development of electric vehicles and portable devices, there is a strong requirement for high-energy batteries. To improve battery energy, multielectron transfer electrode reactions can be applied. Previously, batteries based on fluoride-ion shuttle (F- ion shuttle batteries, FiBs) have been reported, utilizing electrodes with multielectron transfer reactions. Although these FiBs exhibit high theoretical energy densities, reported capacities are significantly less than theoretical values. Moreover, charge-discharge mechanisms are not clarified. In this study, the feasibility of FiBs as extremely high-energy batteries has been demonstrated using a model cell with a Cu cathode and a LaF3 anode. By conducting experiments under an atmosphere without impurities, the Cu/LaF3 battery has been successfully operated with almost theoretical capacity. The Cu/LaF3 battery has been exhibited a superior cycle life at 80 °C, with feasibility for room-temperature operation., 28 Dec. 2020, 33, 1, 459, 466, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Effect of Temperature on Oxygen Reduction Reaction Kinetics for Pd Core–Pt Shell Catalyst with Different Core Size, Chen Liu; Tomoki Uchiyama; Kentaro Yamamoto; Toshiki Watanabe; Xiao Gao; Hideto Imai; Masashi Matsumoto; Seiho Sugawara; Kazuhiko Shinohara; Koichiro Oshima; Shigeki Sakurai; Yoshiharu Uchimoto, The oxygen reduction reaction (ORR) activity and the coverage of oxide species over a Pd core-Pt shell catalyst on carbon support (Pt/Pd/C) with various Pd core sizes (2.3, 4.3, and 8.0 nm) were investigated in the temperature range from 25 to 60 °C and compared with a Pt/C catalyst (TEC10V30E, Tanaka Kikinzoku Kogyo). The apparent rate constant (kapp) of Pt/Pd/C increased with increasing core size at 25 °C. However, kapp of Pt/Pd/C started to decrease at 50-60 °C, while that of Pt/C behaved according to the general Arrhenius equation. Eventually, the 2.3 nm core showed the highest kapp at 60 °C, and the 8.0 nm core was almost the same as that of Pt/C. According to the electrochemical measurements, the coverage of oxide species on Pt/Pd/C was quite smaller than that of Pt/C. However, it increased dramatically with increasing temperature from 25 to 60 °C. Among the Pt/Pd/C, the 8.0 nm core showed the most obvious oxide coverage increase at 60 °C, which was almost identical to that of Pt/C. In contrast, the 2.3 nm core showed the lowest oxide coverage at 60 °C, which was expected to be the cause of the largest kapp. Operando X-ray absorption spectroscopy indicated that the Pt-Pt bond length in Pt/Pd/C was shorter than that in the Pt/C at 25 °C due to compressive surface strain from the Pd core, which is the reason why Pt/Pd/C has higher activity than Pt/C. On the other hand, as Pd has a thermal expansion coefficient higher than that of Pt, Pt/Pd/C showed a Pt-Pt bond length larger than that of Pt/C at 60 °C. A longer Pt-Pt bond length extension was observed at 60 °C in the 8.0 nm core compared to that in the other catalysts., 28 Dec. 2020, 4, 1, 810, 818, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Comparison of Sulfur Cathode Reactions between a Concentrated Liquid Electrolyte System and a Solid-State Electrolyte System by Soft X-Ray Absorption Spectroscopy, Yao Xiao; Kentaro Yamamoto; Yukiko Matsui; Toshiki Watanabe; Atsushi Sakuda; Koji Nakanishi; Tomoki Uchiyama; Akitoshi Hayashi; Shoso Shingubara; Masahiro Tatsumisago; Masashi Ishikawa; Masayoshi Watanabe; Yoshiharu Uchimoto, Sulfur is one of the promising next-generation cathode materials because of its low cost and high theoretical gravimetric capacity. However, the reaction mechanism of the sulfur cathode is largely influenced by the electrolyte and the intermediate sulfur species during the first discharge process has not been quantitatively explored in different electrolytes. In this study, we elucidated the reaction mechanism of sulfide cathodes by using three different electrolyte systems, viz., a conventional liquid electrolyte [LiPF6/ethylene carbonate (EC)/ethylene-methyl carbonate (EMC)], a concentrated liquid electrolyte [lithium bis(trifluorosulfonyl)amide (LiTFSA)/tetraglyme (G4):1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE)], and a solid-state electrolyte (Li3PS4). Soft X-ray absorption spectroscopy was used to examine the reaction mechanism of the sulfur cathode in the liquid and solid-state electrolytes during the first discharge process. In the conventional electrolyte, the sulfur cathode was reduced to long-chain polysulfide (S62-) during the first discharge process, and the polysulfide subsequently dissolved into the electrolyte. In the concentrated electrolyte, the sulfur cathode was reduced to midchain polysulfide (S42-) at the initial stage of the first discharge process and then reduced to short-chain polysulfide (S22-) and Li2S, followed by the formation of long-chain polysulfide (S62-). In the solid-state electrolyte, the sulfur cathode was reduced to long-chain polysulfide (S62-) at the initial stage of the first discharge process and was gradually reduced to mid-chain polysulfide (S42-), short-chain polysulfide (S22-), and Li2S. The differences in these reaction pathways govern electrochemical properties such as the difference in discharge voltage., 17 Dec. 2020, 4, 1, 186, 193, Scientific journal

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• Refereed, ACS Central Science, American Chemical Society (ACS), Nanostructured LiMnO2 with Li3PO4 Integrated at the Atomic Scale for High-Energy Electrode Materials with Reversible Anionic Redox, Miho Sawamura; Sho Kobayakawa; Jun Kikkawa; Neeraj Sharma; Damian Goonetilleke; Aditya Rawal; Nanaka Shimada; Kentaro Yamamoto; Rina Yamamoto; Yingying Zhou; Yoshiharu Uchimoto; Koji Nakanishi; Kei Mitsuhara; Koji Ohara; Jiwon Park; Hye Ryung Byon; Hiroaki Koga; Masaki Okoshi; Toshiaki Ohta; Naoaki Yabuuchi, 15 Dec. 2020, 6, 12, 2326, 2338, Scientific journal

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• Refereed, The Journal of Physical Chemistry C, American Chemical Society (ACS), Effect of Interaction among Magnesium Ions, Anion, and Solvent on Kinetics of the Magnesium Deposition Process, Feilure Tuerxun; Kentaro Yamamoto; Toshihiko Mandai; Yoshitaka Tateyama; Koji Nakanishi; Tomoki Uchiyama; Toshiki Watanabe; Yusuke Tamenori; Kiyoshi Kanamura; Yoshiharu Uchimoto, To clarify the effects of anion species and solvents on the Coulombic efficiency and polarization of magnesium deposition/dissolution reactions, the anode/electrolyte interfacial behavior of magnesium tetrakis(hexafluoroisopropyloxy) borate (Mg[B(HFIP)4]2) and magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA)2) was investigated and compared in triglyme and 2-methlytetrahydrofuran (2-MeTHF). When using triglyme, which has strong interaction with magnesium ions, decomposition of [B(HFIP)4]- in Mg[B(HFIP)4]2/triglyme was hard to occur because of the high reduction stability of the uncoordinated [B(HFIP)4]- anion, resulting in significantly higher Coulombic efficiency and smaller polarization than Mg(TFSA)2/triglyme. When 2-MeTHF was used as the solvent, magnesium deposition/dissolution reactions occurred in the Mg[B(HFIP)4]2/2-MeTHF electrolyte but not in the Mg[TFSA]2/2-MeTHF electrolyte. This is because the coordinated [B(HFIP)4]- anion in Mg[B(HFIP)4]2/2-MeTHF is stable at the magnesium deposition potential. However, the reductive stability of the coordinated [B(HFIP)4]- anion is inferior to that of the uncoordinated [B(HFIP)4]- anion, resulting in the Mg[B(HFIP)4]2/2-MeTHF Coulombic efficiency being lower than that of Mg[B(HFIP)4]2/triglyme. Our results indicate that solvents that could not be used with Mg(TFSA)2 are suitable in weakly coordinating anion electrolytes, such as Mg[B(HFIP)4]2. Controlling the interaction between magnesium ions and anions by selecting suitable anions and solvents is essential for designing new electrolytes for magnesium rechargeable batteries., 15 Dec. 2020, 124, 52, 28510, 28519, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Surface analysis of lanthanum strontium cobalt oxides under cathodic polarization at high temperature through operando total-reflection X-ray absorption and X-ray fluorescence spectroscopy, Yoichiro Tsuji; Shinnosuke Sako; Kiyofumi Nitta; Kentaro Yamamoto; Yang Shao-horn; Yoshiharu Uchimoto; Yuki Orikasa, The surface chemistry of perovskite-type lanthanum transition metal oxides is an important parameter in high-temperature electrochemical devices such as solid oxide fuel cells (SOFCs). Strontium segregation on the surface of lanthanum strontium cobalt oxides (LSC) may lead to poor oxygen reduction kinetics. However, previous studies have not sufficiently addressed the oxide surface chemistry, including the oxidation change of LSC under cathodic polarization. In this study, operando total-reflection X-ray fluorescence absorption and X-ray fluorescence spectroscopy were performed to investigate cathodic polarization at high temperature (773 K) and at 1 atm pressure. Dense thin-film electrodes of La Sr CoO (LSC ) on Zr Y O electrolytes with a gadolinium-doped ceria interlayer were examined as model SOFC cathodes. This may be the first time that predominant surface reduction of cobalt is directly observed by using LSC under cathodic polarization. This phenomenon is related to strontium enrichment on the LSC surface. (La Sr ) CoO decoration on LSC enhanced the oxygen reduction kinetics compared with that of bare LSC . This is due to the suppression of cobalt surface reduction and Sr enrichment in the LSC phase. 0.6 0.4 3 113 0.92 0.08 1.96 113 0.5 0.5 2 4 113 113 113, Dec. 2020, 357, 115502, 115502, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Relationship between rate performance and electronic/structural changes during oxygen redox of lithium-rich 4d/3d transition metal oxides, Aruto Watanabe; Kentaro Yamamoto; Yuki Orikasa; Masatsugu Oishi; Koji Nakanishi; Tomoki Uchiyama; Toshiyuki Matsunaga; Yoshiharu Uchimoto, Li-rich solid solution cathode materials having 3d transition metals or 4d transition metals are the candidate of next generation cathode material. In order to clarify the rate performance of 3d or 4d transition metal oxides, we focused two typical Li-rich solid solution cathodes; Li Ni Co Mn O as a model of 3d transition metal oxide and Li Ni Co Ru O cathode as a model solid solution cathode containing 4d transition metal. We have applied operando hard and soft X-ray absorption spectroscopies clarify electronic and local distortion of both cathodes. From the results of XAS measurements, the reaction mechanism of Li Ni Co Ru O cathode was clearly explained by reversible transition metal redox reaction without the oxygen redox process. The EXAFS analysis suggests that Li Ni Co Ru O cathode also had the small distorted structure around Ru compared with around Mn of Li Ni Co Mn O cathode. The small distorted structure takes advantages for Li diffusion, resulting in the high rate performance of the Li Ni Co Ru O cathode. 1.2 0.13 0.13 0.54 2 1.2 0.13 0.13 0.54 2 1.2 0.13 0.13 0.54 2 1.2 0.13 0.13 0.54 2 1.2 0.13 0.13 0.54 2 1.2 0.13 0.13 0.54 2 +, Dec. 2020, 357, 115459, 115459, Scientific journal

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• Refereed, Solid State Ionics, Elsevier BV, Substrate-dependent proton transport and nanostructural orientation of perfluorosulfonic acid polymer thin films on Pt and carbon substrate, Xiao Gao; Kentaro Yamamoto; Tomoyasu Hirai; Noboru Ohta; Tomoki Uchiyama; Toshiki Watanabe; Masakuni Takahashi; Naoki Takao; Hideto Imai; Seiho Sugawara; Kazuhiko Shinohara; Yoshiharu Uchimoto, The electrochemical reactions occur on the carbon-supported platinum covered by a proton conducting polymer electrolyte. Thus, it is important to clarify the correlation between proton conductivity and morphology of the polymer electrolyte on Pt or carbon. In this study, the properties of thin films (50–200 nm) of Nafion®, which is the typical polymer electrolyte, were investigated on platinum and carbon substrates. Grazing-incidence small/wide angle X-ray scattering and electrochemical impedance spectroscopy were used to extract morphological and proton transport information. Self-designed interdigitated array electrodes were utilized to test and compare the proton conductivity on the Pt and carbon substrates. Based on the results, the difference in anisotropic behavior of Nafion thin films on each substrate were explored, which exhibit that the proton conductivity of Pt-supported Nafion thin films has more well defined hydrophilic domain structure than that of carbon supported thin films along in-plane direction and while it showed the opposite trend in the out-of-plane direction. These datasets and analyses represented a thorough study of the behavior of Nafion thin films on model substrates of interest, i.e., Pt catalyst/carbon electrodes. These results are expected to further understanding the difference in term of proton transport pathway., Dec. 2020, 357, 115456, 115456, Scientific journal

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• Refereed, ChemElectroChem, Wiley, The Effect of Cation Mixing in LiNiO2 toward the Oxygen Evolution Reaction, Yadan Ren; Ryusei Yamaguchi; Tomoki Uchiyama; Yuki Orikasa; Toshiki Watanabe; Kentaro Yamamoto; Toshiyuki Matsunaga; Yoshinori Nishiki; Shigenori Mitsushima; Yoshiharu Uchimoto, Nickel-based oxide catalysts are widely used for the oxygen evolution reaction (OER) in alkaline water electrolysis because of their low cost and high activity. In particular, the LiNiO catalyst shows high activity. Therefore, to elucidate the fundamental relationship between the local structure, catalyst activity, and stability of LiNiO , we investigated the cation mixing effect by mixing sites of lithium and nickel ions in the LiNiO -based catalysts. Lower degrees of cation mixing lead to higher intrinsic OER activity but lower long-term stability. The X-ray absorption spectra (XAS) displayed a strong hybridization state of the Ni 3d and O 2p orbitals, which is the origin of the different catalytic activity behaviors. Meanwhile, operando XAS studies combined with potentiostatic stability tests and inductively coupled plasma optical emission spectrometry (ICP-OES) demonstrated the Li ion loss during the OER process. Thus, the instability of LiNiO originates from de-intercalation of Li ions and this irreversible structure change deteriorates the performance. Hindering the lithium diffusion path by cation mixing is a useful strategy for maintaining performance. This strategy could provide a novel design principle for compatible high activity and long-lasting catalysts by reasonable structure mediation. 2 2 2 2, 17 Nov. 2020, 8, 1, 70, 76, Scientific journal

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• Refereed, ACS Omega, American Chemical Society (ACS), Synthesis of Sulfide Solid Electrolytes through the Liquid Phase: Optimization of the Preparation Conditions, Kentaro Yamamoto; Masakuni Takahashi; Koji Ohara; Nguyen Huu Huy Phuc; Seunghoon Yang; Toshiki Watanabe; Tomoki Uchiyama; Atsushi Sakuda; Akitoshi Hayashi; Masahiro Tatsumisago; Hiroyuki Muto; Atsunori Matsuda; Yoshiharu Uchimoto, All-solid-state lithium batteries using inorganic sulfide solid electrolytes have good safety properties and high rate capabilities as expected for a next-generation battery. Presently, conventional preparation methods such as mechanical milling and/or solid-phase synthesis need a long time to provide a small amount of the product, and they have difficult in supplying a sufficient amount to meet the demand. Hence, liquid-phase synthesis methods have been developed for large-scale synthesis. However, the ionic conductivity of sulfide solid electrolytes prepared via liquid-phase synthesis is typically lower than that prepared via solid-phase synthesis. In this study, we have controlled three factors: (1) shaking time, (2) annealing temperature, and (3) annealing time. The factors influencing lithium ionic conductivity of Li3PS4 prepared via liquid-phase synthesis were quantitatively evaluated using high-energy X-ray diffraction (XRD) measurement coupled with pair distribution function (PDF) analysis. It was revealed from PDF analysis that the amount of Li2S that cannot be detected by Raman spectroscopy or XRD decreased the ionic conductivity. Furthermore, it was revealed that the ionic conductivity of Li3PS4 is dominated by other parameters, such as remaining solvent in the sample and high crystallinity of the sample., 29 Sep. 2020, 5, 40, 26287, 26294, Scientific journal

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• Refereed, Chemical Physics Letters, Elsevier BV, Reversible charge storage of ferrocene-adsorbed activated carbon using ionic liquid electrolytes, Hiroyuki Itoi; Yuto Kasai; Hideyuki Hasegawa; Kentaro Yamamoto; Hiroyuki Iwata; Yoshimi Ohzawa, Jul. 2020, 137795, 137795, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Enhanced Performance Induced by Phase Transition of Li2FeSiO4 upon Cycling at High Temperature, Titus Masese; Yuki Orikasa; Kentaro Yamamoto; Yosuke Hori; Rika Hagiwara; Yoshiharu Uchimoto, 22 Jun. 2020, 3, 6, 5722, 5727, Scientific journal

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• Refereed, ACS Applied Materials & Interfaces, American Chemical Society (ACS), Determining Factor on the Polarization Behavior of Magnesium Deposition for Magnesium Battery Anode, Feilure Tuerxun; Kentaro Yamamoto; Masashi Hattori; Toshihiko Mandai; Koji Nakanishi; Ashu Choudhary; Yoshitaka Tateyama; Keitaro Sodeyama; Aiko Nakao; Tomoki Uchiyama; Masaki Matsui; Kazuki Tsuruta; Yusuke Tamenori; Kiyoshi Kanamura; Yoshiharu Uchimoto, To clarify the origin of the polarization of magnesium deposition/dissolution reactions, we combined electrochemical measurement, operando soft X-ray absorption spectroscopy (operando SXAS), Raman, and density functional theory (DFT) techniques to three different electrolytes: magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA)2)/triglyme, magnesium borohydride (Mg(BH4)2)/tetrahydrofuran (THF), and Mg(TFSA)2/2-methyltetrahydrofuran (2-MeTHF). Cyclic voltammetry revealed that magnesium deposition/dissolution reactions occur in Mg(TFSA)2/triglyme and Mg(BH4)2/THF, while the reactions do not occur in Mg(TFSA)2/2-MeTHF. Raman spectroscopy shows that the [TFSA]- in the Mg(TFSA)2/triglyme electrolyte largely does not coordinate to the magnesium ions, while all of the [TFSA]- in Mg(TFSA)2/2-MeTHF and [BH4]- in Mg(BH4)2/THF coordinate to the magnesium ions. In operando SXAS measurements, the intermediate, such as the Mg+ ion, was not observed at potentials above the magnesium deposition potential, and the local structure distortion around the magnesium ions increases in all of the electrolytes at the magnesium electrode|electrolyte interface during the cathodic polarization. Our DFT calculation and X-ray photoelectron spectroscopy results indicate that the [TFSA]-, strongly bound to the magnesium ion in the Mg(TFSA)2/2-MeTHF electrolyte, undergoes reduction decomposition easily, instead of deposition of magnesium metal, which makes the electrolyte inactive electrochemically. In the Mg(BH4)2/THF electrolyte, because the [BH4]- coordinated to the magnesium ions is stable even under the potential of the magnesium deposition, the magnesium deposition is not inhibited by the decomposition of [BH4]-. Conversely, because [TFSA]- is weakly bound to the magnesium ion in Mg(TFSA)2/triglyme, the reduction decomposition occurs relatively slowly, which allows the magnesium deposition in the electrolyte., 10 Jun. 2020, 12, 23, 25775, 25785, Scientific journal

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• Refereed, physica status solidi (b), Wiley, Observation of liquid phase synthesis of sulfide solid electrolytes using time‐resolved pair distribution function analysis, Koji Ohara; Naoya Masuda; Hiroshi Yamaguchi; Atsushi Yao; Satoshi Tominaka; Hiroki Yamada; Satoshi Hiroi; Masakuni Takahashi; Kentaro Yamamoto; Toru Wakihara; Yoshiharu Uchimoto; Futoshi Utsuno; Shigeru Kimura, Time-resolved pair distribution function (PDF) analysis is performed to clarify the formation mechanism of Li PS sulfide solid electrolytes in liquid phase synthesis with acetonitrile (AN), tetrahydrofuran (THF), and ethyl acetate (EA) solvents. This aims to clarify the relationship between their formations and lithium ionic conductivity. A complex is formed between the precursor of the sulfide solid electrolyte and each solvent during the liquid phase synthesis. The ratio of the solvent to the electrolyte is 3.03 in THF solution. The formation speed of precursors of sulfide solid electrolytes increases in the order AN < THF < EA solution, which is the same order as the lithium ionic conductivity. Thus, the correlation between the ionic conductivity and the formation rate of the precursor of the sulfide solid electrolyte might be related to the stability of the complex formed between Li PS and the solvent during liquid phase synthesis. 3 4 3 4, 09 Jun. 2020, 257, 11, Scientific journal

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• Refereed, Science Advances, American Association for the Advancement of Science (AAAS), A reversible oxygen redox reaction in bulk-type all-solid-state batteries, Kenji Nagao; Yuka Nagata; Atsushi Sakuda; Akitoshi Hayashi; Minako Deguchi; Chie Hotehama; Hirofumi Tsukasaki; Shigeo Mori; Yuki Orikasa; Kentaro Yamamoto; Yoshiharu Uchimoto; Masahiro Tatsumisago, An all-solid-state lithium battery using inorganic solid electrolytes requires safety assurance and improved energy density, both of which are issues in large-scale applications of lithium-ion batteries. Utilization of high-capacity lithium-excess electrode materials is effective for the further increase in energy density. However, they have never been applied to all-solid-state batteries. Operational difficulty of all-solid-state batteries using them generally lies in the construction of the electrode-electrolyte interface. By the amorphization of Li₂RuO₃ as a lithium-excess model material with Li₂SO₄, here, we have first demonstrated a reversible oxygen redox reaction in all-solid-state batteries. Amorphous nature of the Li₂RuO₃-Li₂SO₄ matrix enables inclusion of active material with high conductivity and ductility for achieving favorable interfaces with charge transfer capabilities, leading to the stable operation of all-solid-state batteries., Jun. 2020, 6, 25, eaax7236, eaax7236, Scientific journal

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• Refereed, Solid State Ionics, Reaction mechanism of electrochemical insertion/extraction of magnesium ions in olivine-type FePO4, Aruto Watanabe; Kentaro Yamamoto; Yuki Orikasa; Titus Masese; Takuya Mori; Tomoki Uchiyama; Toshiyuki Matsunaga; Yoshiharu Uchimoto, © 2020 Elsevier B.V. In order to develop suitable cathodes for practical magnesium rechargeable batteries, it is important to understand the differences between the mechanisms of lithium ions and magnesium ions insertion/extraction reactions in cathode materials. We used olivine-type FePO4 as a model material to examine the mechanism of magnesium ions insertion/extraction reactions by performing galvanostatic measurements, X-ray absorption spectroscopy, and synchrotron X-ray diffraction (XRD) analysis. The equilibrium potential of MgxFePO4 gradually changed with magnesium ions insertion/extraction. In the XRD patterns of MgxFePO4, the only peak shift was observed without second phase formation. It was proved that the magnesium ions insertion/extraction in FePO4 proceeded not by a two-phase reaction, but by a single-phase reaction., Jun. 2020, 349, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society (ACS), Capacity Improvement by Nitrogen Doping to Lithium-Rich Cathode Materials with Stabilization Effect of Oxide Ions Redox, Aruto Watanabe; Kentaro Yamamoto; Tomoki Uchiyama; Toshiyuki Matsunaga; Akitoshi Hayashi; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, Lithium-rich cathode materials show higher theoretical capacity than conventional cathode materials because the redox activity of oxide ions in addition to the transition metal valence change contributes charge compensation during charge/discharge reactions. In this study, we prepared nitrogen-doped lithium-rich cathode materials, Li1.2Ti0.4Mn0.4O2, by using mechanical milling with Li3N. The optimized nitrogen-doped Li1.2Ti0.4Mn0.4O1.85N0.10 showed higher first charge capacity of 350 mAh g-1 than that of the non-nitrogen-doped Li1.2Ti0.4Mn0.4O2 of 300 mAh g-1. Soft X-ray absorption spectroscopy indicated that the extra capacity was contributed to by both Mn valence change and oxide ions redox., 26 May 2020, 3, 5, 4162, 4167, Scientific journal

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• Refereed, Langmuir, Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions, Xiao Gao; Kentaro Yamamoto; Tomoyasu Hirai; Tomoki Uchiyama; Noboru Ohta; Naoki Takao; Masashi Matsumoto; Hideto Imai; Seiho Sugawara; Kazuhiko Shinohara; Yoshiharu Uchimoto, Copyright © 2020 American Chemical Society. The morphological changes of Nafion thin films with thicknesses from 10 to 200 nm on Pt substrate with various annealing histories (unannealed to 240 °C) were systematically investigated using grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS). The results revealed that the hydrophilic ionic domain and hydrophobic backbone in Nafion thin films changed significantly when the annealing treatment exceeded the cluster transition temperature, which decreased proton conductivity, due to the constrained hydrophilic/hydrophobic phase separation, and increased the crystalline-rich domain. This research contributed to the understanding of ionomer thermal stability in the catalyst layer, which is subjected to thermal annealing during the hot-pressing process., Apr. 2020, 36, 14, 3871, 3878, Scientific journal

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• Refereed, JOURNAL OF ALLOYS AND COMPOUNDS, ELSEVIER SCIENCE SA, Structural analysis of imperfect Li2TiO3 crystals, Watanabe, Aruto; Matsunaga, Toshiyuki; Abulikemu, Aierxiding; Shimoda, Keiji; Yamamoto, Kentaro; Uchiyama, Tomoki; Uchimoto, Yoshiharu, Li2TiO3 is a Li-rich cathode/anode material similar to Li2MnO3. These materials crystallize into monoclinic structures with ABC-stacked atomic layers, approximated by pseudo-trigonal cells. In these crystals, transition-metal layers are occupied not only by transition-metal atoms but also by Li atoms, forming ordered/disordered atomic arrangements. Faults Rietveld analysis was conducted, showing that Li2TiO3 crystalizes into a monoclinic structure with the space group C2/c, in which Li and Ti atoms are configured in an imperfectly ordered arrangement at the transition-metal layer and a large number of stacking faults are generated in the crystal. To precisely evaluate the site occupancies in such imperfect crystals, our structural analysis found that the structures should be analyzed by powder diffraction while taking stacking faults and atomic mixing into account. The atomic mixing at the transition-metal layer tends to gradually increase as the synthesis temperature is raised. (C) 2019 Elsevier B.V. All rights reserved., Apr. 2020, 819, Scientific journal

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• Refereed, CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, Noncrystalline Nanocomposites as a Remedy for the Low Diffusivity of Multivalent Ions in Battery Cathodes, Yuki Orikasa; Kazuaki Kisu; Etsuro Iwama; Wako Naoi; Yusuke Yamaguchi; Yoshitomo Yamaguchi; Naohisa Okita; Koji Ohara; Toshiyuki Munesada; Masashi Hattori; Kentaro Yamamoto; Patrick Rozier; Patrice Simon; Katsuhiko Naoi, Rechargeable batteries using multivalent metals are among the most promising next-generation battery systems due to their high capacity, high safety, and low cost compared with lithium-ion batteries. However, strong cation anion interaction degrades diffusion in solid cathodes, an effect that must be mitigated to yield practical multivalent metal batteries. We show that a highly defective iron phosphate carbon composite prepared by ultracentrifugation serves as a reversible insertion/deinsertion for magnesium ions with, and operates beyond, a 2-V cell voltage at room temperature. A composite of noncrystalline particles that embeds the surrounding carbon structure enhances the magnesium-ion diffusion in the solid phase with stability for cycle life. X-ray absorption spectroscopy, transmission electron microscopy with energy-dispersive X-ray spectroscopy, and high-energy X-ray scattering measurements demonstrate magnesium-ion insertion and extraction in the defective iron phosphate without conversion reactions. This work suggests promising applications for highly defective structures as intercalation hosts for multivalent ions., Feb. 2020, 32, 3, 1011, 1021, Scientific journal

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• Refereed, Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), Understanding the Reaction Mechanism and Performances of 3d Transition Metal Cathodes for All-solid-state Fluoride Ion Batteries, Datong Zhang; Kentaro Yamamoto; Aika Ochi; Yanchang Wang; Takahiro Yoshinari; Koji Nakajishi; Hiroyuki Nakano; Hidenori Miki; Shinji Nakanishi; Hideki Iba; Tomoki Uchiyama; Toshiki Watanabe; Koji Amezawa; Yoshiharu Uchimoto,

  Fluoride ion batteries (FIBs) are regarded as promising energy storage devices, and it is important and urgent to develop cathode materials with high energy densities for use in FIBs. However,...

  , 2020, 9, 1, 406, 412, Scientific journal

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• Refereed, RSC Advances, Royal Society of Chemistry (RSC), Operando soft X-ray absorption spectroscopic study on microporous carbon-supported sulfur cathodes, Yao Xiao; Kentaro Yamamoto; Yukiko Matsui; Toshiki Watanabe; Koji Nakanishi; Tomoki Uchiyama; Shoso Shingubara; Masashi Ishikawa; Masayoshi Watanabe; Yoshiharu Uchimoto,

  The reaction mechanism of the sulfur cathode in the microporous carbon during discharge was observed by operando XAS.

  , 2020, 10, 65, 39875, 39880, Scientific journal

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• Refereed, Electrochemistry, The Electrochemical Society of Japan, Operando X-ray Absorption Spectroscopic Study on the Effect of Ionic Liquid Coverage upon the Oxygen Reduction Reaction Activity of Pd-core Pt-shell Catalysts, Tomoki UCHIYAMA; Chen LIU; Jyunichi ISHIHARA; Kentaro YAMAMOTO; Toshiki WATANABE; Hideto IMAI; Koichiro OSHIMA; Shigeki SAKURAI; Minoru INABA; Yoshiharu UCHIMOTO, 2020, 89, 1, 31, 35, Scientific journal

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• Refereed, Electrochemistry, The Electrochemical Society of Japan, Investigation of Cathodic Reaction Mechanism in Solid Oxide Fuel Cells by Operando X-Ray Absorption Spectroscopy, Yoichiro TSUJI; Koji AMEZAWA; Takayuki NAKAO; Toshiaki INA; Tatsuya KAWADA; Kentaro YAMAMOTO; Yoshiharu UCHIMOTO; Yuki ORIKASA, 2020, 88, 6, 560, 565, Scientific journal

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• Refereed, CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, Charge Compensation Mechanism of Lithium-Excess Metal Oxides with Different Covalent and Ionic Characters Revealed by Operando Soft and Hard X-ray Absorption Spectroscopy, Yamamoto, Kentaro; Zhou, Yingying; Yabuuchi, Naoaki; Nakanishi, Koji; Yoshinari, Takahiro; Kobayashi, Takanori; Kobayashi, Yuki; Yamamoto, Rina; Watanabe, Aruto; Orikasa, Yuki; Tsuruta, Kazuki; Park, Jiwon; Byon, Hye Ryung; Tamenori, Yusuke; Ohta, Toshiaki; Uchimoto, Yoshiharu, The charge/discharge capacity of current lithium-ion battery cathode materials is limited by the charge compensation of transition-metal redox during the charge/discharge processes. Recently, the use of oxide ion redox for charge compensation has been proposed to realize a higher charge/discharge capacity than that observed for transition metal redox. Different stabilization mechanisms of the reversible oxide ion redox have been proposed. To clarify the mechanism, analysis of the electronic and local structures around oxygen is required. Because of the high-voltage region in which the oxide ion redox occurs, several reactions such as oxygen gas evolution and/or electrolyte oxidation are often included. Thus, operando measurements are required to directly prove this concept and generalize the understanding of the oxide ion redox. This study employs operando soft/hard X-ray absorption spectroscopy combined with X-ray diffraction spectroscopy for four lithium-excess electrode materials with different chemical bond natures. The experimental data together with online analysis of the generated on-charge gas reveal two extreme cases: significantly enhanced covalent or ionic characters in the metal oxygen chemical bonds, which are necessary conditions to stabilize the oxidation of the oxide ions. This finding provides new insights with exciting possibilities for designing high energy density cathode materials based on anion redox., Jan. 2020, 32, 1, 139, 147, Scientific journal

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• Refereed, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, Observation of Subsurface Structure of Pt/C Catalyst Using Pair Distribution Function and Simple Modeling Techniques, Masakuni Takahashi; Koji Ohara; Kentaro Yamamoto; Tomoki Uchiyama; Hajime Tanida; Takanori Itoh; Hideto Imai; Seiho Sugawara; Kazuhiko Shinohara; Yoshiharu Uchimoto, The correlation between the Pt-Pt interatomic distance of a Pt/C catalyst and the specific activity of the oxygen reduction reaction is discussed. Total X-ray scattering measurement coupled with pair distribution function (PDF) analysis was performed to obtain subsurface information of the Pt/C catalyst, which can obtain a much longer interatomic distance than X-ray absorption fine structure (XAFS) measurement. The subsurface structure of the catalyst was previously discussed on the basis of simulations with three-dimensional complex models. In this study, the subsurface structure of Pt-Pt bonds in the catalyst could be easily obtained from experimental data by simple model fitting using the PDF. Results based on XAFS measurement showed no correlation with the specific activity. In contrast, the obtained Pt-Pt interatomic distances in the subsurface using PDF showed a strong negative correlation with the specific activity as in a previous study., Jan. 2020, 93, 1, 37, 42, Scientific journal

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• Refereed, Physical Review B, American Physical Society (APS), Identification of ferrimagnetic orbitals preventing spinel degradation by charge ordering in LixMn2O4, Hasnain Hafiz; Kosuke Suzuki; Bernardo Barbiellini; Yuki Orikasa; Stanislaw Kaprzyk; Naruki Tsuji; Kentaro Yamamoto; Ayumu Terasaka; Kazushi Hoshi; Yoshiharu Uchimoto; Yoshiharu Sakurai; Hiroshi Sakurai; Arun Bansil, 04 Nov. 2019, 100, 20, Scientific journal

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• Refereed, CHEMISTRY OF MATERIALS, Quantitative Elucidation of the Non-Equilibrium Phase Transition in LiFePO4 via the Intermediate Phase, Yoshinari Takahiro; Mori Takuya; Otani Kazufumi; Munesada Toshiyuki; Yamamoto Kentaro; Uchiyama Tomoki; Fukuda Katsutoshi; Koyama Yukinori; Hagiwara Rika; Orikasa Yuki; Uchimoto Yoshiharu, Phase-transition route according to compositional change strongly affects the reaction kinetics within materials in energy devices such as lithium-ion batteries. The promising electrode material of LiFePO exhibits a high rate performance due to the crucial but controversial act of the metastable intermediate phase in addition to the end members of the two phases at room temperature. Here, we investigated the electrochemical and crystal structural behavior of the intermediate phase in Li FePO to be thermodynamically stable at elevated temperature. The current-induced intermediate phase was detected by electrochemical measurements as well as operando X-ray diffraction using a molten salt electrolyte at 230 °C and shows hysteretic charge/discharge characteristics. The nucleation of the intermediate phase occurs at its composition of x = 0.64-0.65 in the independent reaction direction. Both the composition of the intermediate phase and the total composition of Li FePO are equal on the charge and not on the discharge. This discrepancy produces the unexpected results that the sequential phase transition via the intermediate phase as a single phase proceeds on the charge, but the three phases coexist in a whole reaction on the discharge. The charge process is a kinetically favorable direction for a current-induced phase transition being responsible for the intermediate phase. This phase-transition mechanism could be deduced to the actual environment. The formation of the intermediate phase is important, as its further stabilization leads to an extension of a single-phase reaction, realizing high-rate electrode materials. 4 x 4 x 4, 24 Sep. 2019, 31, 18, 7160, 7166, Scientific journal

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• Refereed, Journal of Power Sources, Exothermal mechanisms in the charged LiNi1/3Mn1/3Co1/3O2 electrode layers for sulfide-based all-solid-state lithium batteries, Hirofumi Tsukasaki; Tomoki Uchiyama; Kentaro Yamamoto; Shigeo Mori; Yoshiharu Uchimoto; Hiroe Kowada; Akitoshi Hayashi; Masahiro Tatsumisago, © 2019 Elsevier B.V. Sulfide-based all-solid-state lithium batteries are a possible next-generation power source due to their incombustibility and large energy density. A composite comprising LiNi1/3Mn1/3Co1/3O2 (NMC) and 75Li2S·25P2S5 (LPS) glass electrolytes are used as a positive electrode material, which exhibits excellent charge–discharge cycle characteristics. In this study, to understand the origin of exothermal reactions during heating, we investigated structural changes in initially charged NMC–LPS composites mainly by in-situ synchrotron X-ray diffraction measurements and ex-situ transmission electron microscopy observations. We found that significant structural changes occurred in the NMC–LPS composites after heating above 300 °C. NMC decomposed into transition metal sulfides, such as MnS and CoNi2S4, while crystallization occurred in LPS predominantly precipitating a Li3PO4 crystalline phase. The formation of Li3PO4 is attributable to oxidation reactions between Li3PS4 and oxygen, which was generated during NMC decomposition. Thus, the exothermic peaks that were characteristic of the charged NMC–LPS composites are fundamentally related to heat generation that accompanies the formation of transition metal sulfides and Li3PO4 crystalline phases. As a result, when exposed to real cell operating environments, LPS and NMC yield a chemical reaction via heat treatment that leads to the exothermal reactions., 15 Sep. 2019, 434, Scientific journal

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• Refereed, The Journal of Physical Chemistry C, American Chemical Society ({ACS}), 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, Kezheng Chen; Sae Shinjo; Atsushi Sakuda; Kentaro Yamamoto; Tomoki Uchiyama; Kentaro Kuratani; Tomonari Takeuchi; Yuki Orikasa; Akitoshi Hayashi; Masahiro Tatsumisago; Yuta Kimura; Takashi Nakamura; Koji Amezawa; Yoshiharu Uchimoto, In sheet-type all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte, composite electrodes consist of active material, solid electrolyte, conductive additive material, and binder. Thus, they form a three-dimensional ionic and electronic conduction pass. In composite electrodes, the reaction inhomogeneity derived from their morphology exerts a remarkable effect on battery performance. In this study, we prepared sheet-type composite electrodes for all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte using different binder materials with different solvents and investigated the reaction distribution within the electrodes using the 2D-imaging X-ray absorption spectroscopy. Thus, we demonstrated that the dominant factor of the reaction distribution formation is the ionic conduction, depending on the structure of the composite electrode, and that the structure is influenced by the combination between the binder and the solvent used in the preparation of the sheet-type composite electrode., Feb. 2019, 123, 6, 3292, 3298, Scientific journal

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• Refereed, SOLID STATE IONICS, ELSEVIER SCIENCE BV, Effect of introducing interlayers into electrode/electrolyte interface in all solid-state battery using sulfide electrolyte, Chen, Kezheng; Yamamoto, Kentaro; Orikasa, Yuki; Uchiyama, Tomoki; Ito, Yusuke; Yubuchi, So; Hayashi, Akitoshi; Tatsumisago, Masahiro; Nitta, Kiyofumi; Uruga, Tomoya; Uchimoto, Yoshiharu, Introduction of an interlayer between a cathode and a sulfide solid electrolyte is a well-known method ft reducing the interfacial resistance and improving the performance of all-solid-state batteries. However, tF mechanism responsible for the interlayer remains unclear because it is difficult to observe the reactions at tf nanometer-scale range. In this study, thin-film model interface of LiCoO2/80Li(2)S.20P(2)S(5) and LiCoO2/Li3PO4, 8OLi(2)S.20P(2)S(5) are fabricated by pulsed-laser deposition. The model interfaces are investigated by performin electrochemical measurements and depth-resolved X-ray absorption spectroscopy to clarify the effect of tt Li3PO4 interlayer. The results indicate that a reaction product layer forms between the LiCoO2 cathode and 80Li(2)S-20P(2)S(5) electrolyte during charge/discharge processes, resulting in high interfacial resistance. Meanwhile the formation of the reaction product layer can be suppressed by the introduction of a Li3PO4 interlayer., Dec. 2018, 327, 150, 156, Scientific journal

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• Refereed, ACS Applied Energy Materials, American Chemical Society ({ACS}), High Rate Performance of Dual-Substituted LiFePO4 Based on Controlling Metastable Intermediate Phase, Takahiro Yoshinari; Kentaro Yamamoto; Motoaki Nishijima; Katsutoshi Fukuda; Akihide Kuwabara; Isao Tanaka; Kazuhiko Maeda; Hiroshi Kageyama; Yuki Orikasa; Yoshiharu Uchimoto, High rate capability is one of the most important properties in Li-ion batteries for electric vehicle and/or energy grid use. Herein, a high-power electrode material consisting of dual-substituted LiFePO by zirconium and silicon, Li(Fe Zr )(P Si )O , was developed as it exhibits small lattice volume change between Li-rich and Li-poor phases. The dual-substituted cathode exhibited 1.1-4.4 times larger charge/discharge capacities for upper 10 C rates than that of the undoped material. Time-resolved XRD measurements at the high rate of 10 C revealed the formation of a metastable intermediate phase during the Li intercalation/deintercalation processes which triggers the continuous phase transition in Li(Fe Zr )(P Si )O with moderation of the lattice mismatch. Controlling the lattice volume change between the initial and end phase of the intercalation materials is key to achieving high rate capabilities. 4 0.95 0.05 0.9 0.1 4 0.95 0.05 0.9 0.1 4, Dec. 2018, 1, 12, 6736, 6740, Scientific journal

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• Refereed, The Journal of Physical Chemistry C, American Chemical Society ({ACS}), Role of Coordination Structure of Magnesium Ions on Charge and Discharge Behavior of Magnesium Alloy Electrode, Masashi Hattori; Kentaro Yamamoto; Masaki Matsui; Koji Nakanishi; Toshihiko Mandai; Ashu Choudhary; Yoshitaka Tateyama; Keitaro Sodeyama; Tomoki Uchiyama; Yuki Orikasa; Yusuke Tamenori; Tatsuya Takeguchi; Kiyoshi Kanamura; Yoshiharu Uchimoto, Mechanism of magnesium ion alloying reaction into bismuth electrode in magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA)2)/acetonitrile (AN) and Mg(TFSA)2/2-methyltetrahydrofuran (2-MeTHF) electrolyte was examined by a combination of operando soft X-ray absorption spectroscopy (XAS), Raman spectroscopy, and density functional theory (DFT) calculations. In 0.5 M Mg(TFSA)2/AN, the magnesium ions alloying reaction occurred, whereas the alloying reaction did not occur in 0.5 M Mg(TFSA)2/2-MeTHF. Raman spectroscopy showed that less than 15% of [TFSA]- coordinates with magnesium ions in 0.5 M Mg(TFSA)2/AN, while more than 90% of [TFSA]- coordinates with magnesium ions in Mg(TFSA)2/2-MeTHF. Using operando XAS measurements, we observed that electronic and local structure of magnesium ion changed similarly upon cathodic polarization in both electrolytes. These results indicate that the difference of the behavior of alloy formation should be affected by the difference of coordinate structure of [TFSA]- in both electrolytes. Our DFT calculation results indicates [TFSA]- coordinated to magnesium ions undergoes reduction decomposition more easily than [TFSA]- uncoordinated to magnesium ions. In 0.5 M Mg(TFSA)2/2-MeTHF, the [TFSA]- coordinating to magnesium ions undergoes reduction decomposition, which inhibits the alloying reaction into the bismuth electrode. On the other hand, in 0.5 M Mg(TFSA)2/AN, the [TFSA]- reduction decomposition occurs relatively slowly because of the weak coordination between [TFSA]- and magnesium ions, which allows the magnesium ions alloying into the bismuth electrode in the electrolyte., Nov. 2018, 122, 44, 25204, 25210, Scientific journal

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• Refereed, Journal of Surface Analysis, Investigation of charge compensation mechanism of LiNi1/3Co1/3Mn1/3O2 Positive Electrode during Initial Charge Process by Operando Soft X-ray XAFS Measurement, 中西康次; 中西康次; 北田耕嗣; 北田耕嗣; 森田善幸; 谷田肇; 為則雄祐; 鶴田一樹; 家路豊成; 折笠有基; 山本健太郎; 内本喜晴; 小久見善八; 太田俊明, Aug. 2018, 25, 2, 90, 102
• Refereed, ENERGY STORAGE MATERIALS, ELSEVIER, Grain-boundary-rich mesoporous NiTiO3 micro-prism as high tap-density, super rate and long life anode for sodium and lithium ion batteries, Huang, Zhen-Dong; Zhang, Ting-Ting; Lu, Hao; Masese, Titus; Yamamoto, Kentarou; Liu, Rui-Qing; Lin, Xiu-Jing; Feng, Xiao-Miao; Liu, Xian-Ming; Wang, Dan; Uchimoto, Yoshiharu; Ma, Yan-Wen, Titanium based compounds, such as TiO2, Li5Ti4O12 and Na2TinO2n+1 (where n = 3-8), have been pursued intensively for high energy and high power sodium and lithium ion batteries (NIBs and LIBs). Beside high rate and long life, the relatively higher capacity, higher tap density, scalable preparation process and low production cost are also essential factors for promising anode materials to progress from laboratory scale to pilot scale and finally to commercially scale up. Therefore, a dual-metal-organic crystal derived NiTiO3 mesoporous microprism is developed by a scalable and unique self-assembly process. The interesting assembling mechanism is also clearly discussed based on the colour and microstructure evolutions of the reaction solution at different stage. The obtained NiTiO3 hexagonal micro-prism features interconnected grain-boundary-rich and mesoporous structure, endowing highly conductive path for charge transportation and shortcut for ion diffusion. Together with a high tap density (2.5 g cm(-3)), this anode materials can deliver a high capacity of 373 and 562 mAh g(-1) with superior rate and capacity retention for both sodium and lithium ion storage, respectively. It is also noteworthy that even after cycling for 1000 cycles at 5000 mA g(-1), the capacity retention ratio is maintained at 44.3% and 60.4% for sodium and lithium ion storage, respectively. The superior electrochemical properties, coupled with the low cost, dense structure and the scalable preparation method, will bring NiTiO3 micro-prism to the fore as a promising contender anode material for long durability and high power compact NIBs and LIBs., Jul. 2018, 13, 329, 339, Scientific journal

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• Refereed, SCIENCE ADVANCES, AMER ASSOC ADVANCEMENT SCIENCE, Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering, Hasnain Hafiz; Kosuke Suzuki; Bernardo Barbiellini; Yuki Orikasa; Vincent Callewaert; Staszek Kaprzyk; Masayoshi Itou; Kentaro Yamamoto; Ryota Yamada; Yoshiharu Uchimoto; Yoshiharu Sakurai; Hiroshi Sakurai; Arun Bansil, Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials., Aug. 2017, 3, 8, Scientific journal

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• Refereed, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, Dynamic Behavior at the Interface between Lithium Cobalt Oxide and an Organic Electrolyte Monitored by Neutron Reflectivity Measurements, Taketoshi Minato; Hiroyuki Kawaura; Masaaki Hirayama; Sou Taminato; Kota Suzuki; Norifumi L. Yamada; Hidetaka Sugaya; Kentaro Yamamoto; Koji Nakanishi; Yuki Orikasa; Hajime Tanida; Ryoji Kanno; Hajime Arai; Yoshiharu Uchimoto; Zempachi Ogumi, Clarification of the interaction between the electrode and the electrolyte is crucial for further improvement of the performance of lithium-ion batteries. We have investigated the structural change at the interface between the surface of a 104-oriented epitaxial thin film of LiCoO2 (LiCoO2(104)), which is one of the stable surfaces of LiCoO2, and an electrolyte prepared using a carbonate solvent (1 M LiClO4 in ethylene carbonate and dimethyl carbonate) by in situ neutron reflectivity measurements. Owing to the decomposition of the organic solvent, a new interface layer was formed after contact of LiCoO2(104) with the electrolyte. The composition and thickness of the interface layer changed during Li+ extraction/insertion. During Li+ extraction, the thickness of the interface layer increased and the addition of an inorganic species is suggested. The thickness of the interface layer decreased during Li+ insertion. We discuss the relationship between battery performance and the dynamic behavior at the interface., Sep. 2016, 120, 36, 20082, 20088, Scientific journal

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• Not Refereed, APPLIED PHYSICS LETTERS, AMER INST PHYSICS, Identifying a descriptor for d-orbital delocalization in cathodes of Li batteries based on x-ray Compton scattering, B. Barbiellini; K. Suzuki; Y. Orikasa; S. Kaprzyk; M. Itou; K. Yamamoto; Yung Jui Wang; H. Hafiz; R. Yamada; Y. Uchimoto; A. Bansil; Y. Sakurai; H. Sakurai, We discuss how x-ray Compton scattering spectra can be used for investigating the evolution of electronic states in cathode materials of Li batteries under the lithiation/delithiation process. In particular, our analysis of the Compton spectra taken from polycrystalline LixCoO2 samples shows that the spectra are dominated by the contribution of the O-2p redox orbital. We identify a distinct signature of d-orbital delocalization, which is tied directly to the conductivity of the material, providing a descriptor based on Compton spectra for monitoring the lithiation range with improved conductivity and kinetics for electrochemical operation. Our study demonstrates that Compton scattering spectroscopy can provide a window for probing complex electronic mechanisms underlying the charging and discharging processes in Li-battery materials. Published by AIP Publishing., Aug. 2016, 109, 7, Scientific journal

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• Refereed, SCIENTIFIC REPORTS, NATURE PUBLISHING GROUP, Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution, Yuki Orikasa; Yuma Gogyo; Hisao Yamashige; Misaki Katayama; Kezheng Chen; Takuya Mori; Kentaro Yamamoto; Titus Masese; Yasuhiro Inada; Toshiaki Ohta; Zyun Siroma; Shiro Kato; Hajime Kinoshita; Hajime Arai; Zempachi Ogumi; Yoshiharu Uchimoto, Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances., May 2016, 6, Scientific journal

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• Refereed, JOURNAL OF APPLIED PHYSICS, AMER INST PHYSICS, Non-destructive measurement of in-operando lithium concentration in batteries via x-ray Compton scattering, K. Suzuki; B. Barbiellini; Y. Orikasa; S. Kaprzyk; M. Itou; K. Yamamoto; Yung Jui Wang; H. Hafiz; Y. Uchimoto; A. Bansil; Y. Sakurai; H. Sakurai, Non-destructive determination of lithium distribution in a working battery is key for addressing both efficiency and safety issues. Although various techniques have been developed to map the lithium distribution in electrodes, these methods are mostly applicable to test cells. Here, we propose the use of high-energy x-ray Compton scattering spectroscopy to measure the local lithium concentration in closed electrochemical cells. A combination of experimental measurements and parallel first-principles computations is used to show that the shape parameter S of the Compton profile is linearly proportional to lithium concentration and thus provides a viable descriptor for this important quantity. The merits and applicability of our method are demonstrated with illustrative examples of LixMn2O4 cathodes and a working commercial lithium coin battery CR2032. (C) 2016 AIP Publishing LLC., Jan. 2016, 119, 2, Scientific journal

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• Refereed, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, Crystal Structural Changes and Charge Compensation Mechanism during Two Lithium Extraction/Insertion between Li2FeSiO4 and FeSiO4, Titus Masese; Cedric Tassel; Yuki Orikasa; Yukinori Koyama; Hajime Arai; Naoaki Hayashi; Jungeun Kim; Takuya Mori; Kentaro Yamamoto; Yoji Kobayashi; Hiroshi Kageyama; Zempachi Ogumi; Yoshiharu Uchimoto, Li2FeSiO4 is a promising cathode material for lithium ion batteries because of its theoretically high capacity if two lithium ions can be extracted/inserted per formula unit; however, the extraction/insertion of two lithium ions from Li2FeSiO4 remains a challenge. Herein, we successfully synthesized carbon-coated Li2FeSiO4 nanoparticles which exhibit a capacity commensurate to a reversible two-lithium extraction/insertion at elevated temperature. This study investigates the mechanism underlying a two lithium ion extraction/insertion in Li2FeSiO4 using synchrotron X-ray absorption spectroscopy and X-ray diffraction. Our results reveal that the contribution of the Fe-3d band is dominant for the first lithium extraction process from Li2FeSiO4 to LiFeSiO4. During the second lithium extraction process from LiFeSiO4 to FeSiO4, however, ligand holes are formed in the O-2p band rather than further oxidation of Fe3+. Structural analyses further reveal a phase transformation between Li2FeSiO4 and LiFeSiO4, while a single-phase behavior is observed for Li2-xFeSiO4 (1.0 <= x <= 2.0). Together with a tentatively refined crystal structure of the FeSiO4 phase (x = 2.0), we discuss the charge compensation mechanism during two lithium extraction/insertion in Li2FeSiO4., May 2015, 119, 19, 10206, 10211, Scientific journal

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• Refereed, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, Effect of an Electrolyte Additive of Vinylene Carbonate on the Electronic Structure at the Surface of a Lithium Cobalt Oxide Electrode under Battery Operating Conditions, Daiko Takamatsu; Yuki Orikasa; Shinichiro Mori; Takayuki Nakatsutsumi; Kentaro Yamamoto; Yukinori Koyama; Taketoshi Minato; Tatsumi Hirano; Hajime Tanida; Hajime Arai; Yoshiharu Uchimoto; Zempachi Ogumi, Lifetimes of lithium-ion batteries are often affected by deterioration of positive electrodes. It is well-known that the deterioration of the positive electrodes can be reduced by using electrolyte additives; however, the mechanism underlying this cyclability improvement needs to be clarified. In this study, we investigate electronic structure at the electrode/electrolyte interface using in situ total-reflection fluorescence X-ray absorption spectroscopy to elucidate the mechanism underlying the cyclability improvement of a LiCoO2 electrode upon addition of vinylene carbonate (VC) to the electrolyte. The results indicate that the reduction of cobalt ions at the surface of the LiCoO2 electrode, which occurs upon soaking in the electrolyte in the absence of VC, is suppressed by the presence of the VC additive. The VC additive also suppresses irreversible change in the electronic structure of the cobalt ions at the LiCoO2 surface during successive charge/discharge processes. The effects of the VC additive can be attributed to the formation of a layer of decomposed VC molecules at the LiCoO2/electrolyte interface, which plays an important role in the suppression of the irreversibility at the LiCoO2 surface during the charge/discharge processes., May 2015, 119, 18, 9791, 9797, Scientific journal

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• Refereed, PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, Extracting the Redox Orbitals in Li Battery Materials with High-Resolution X-Ray Compton Scattering Spectroscopy, K. Suzuki; B. Barbiellini; Y. Orikasa; N. Go; H. Sakurai; S. Kaprzyk; M. Itou; K. Yamamoto; Y. Uchimoto; Yung Jui Wang; H. Hafiz; A. Bansil; Y. Sakurai, We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn(2)O(4), a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16 +/- 0.05 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery., Feb. 2015, 114, 8, Scientific journal

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• Refereed, RSC ADVANCES, ROYAL SOC CHEMISTRY, Vanadium phosphate as a promising high-voltage magnesium ion (de)-intercalation cathode host, Zhen-Dong Huang; Titus Masese; Yuki Orikasa; Takuya Mori; Kentarou Yamamoto, Magnesium batteries (MBs) have been considered as one of the most promising safe and lowcost energy storage systems. Herein, vanadium phosphates, prepared by the electrochemical de-lithiation of Li3V2(PO4)(3), are investigated as a high-voltage cathode host for Mg2+ (de)-intercalation. The reversible (de)-intercalation of Mg2+ into (from) the host structure of V-2(PO4)(3) are verified by the comprehensive analysis of the results from the electrochemical tests, synchrotron Xray diffraction and absorption, and inductively coupled plasma measurements. Its exceptional high average working voltage (similar to 3.0 V vs. Mg/Mg2+) surpasses other reported values of cathode hosts for MBs., 2015, 5, 12, 8598, 8603, Scientific journal

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• Refereed, ADVANCED MATERIALS INTERFACES, WILEY, Origin of Surface Coating Effect for MgO on LiCoO2 to Improve the Interfacial Reaction between Electrode and Electrolyte, Yuki Orikasa; Daiko Takamatsu; Kentaro Yamamoto; Yukinori Koyama; Shinichiro Mori; Titus Masese; Takuya Mori; Taketoshi Minato; Hajime Tanida; Tomoya Uruga; Zempachi Ogumi; Yoshiharu Uchimoto, Surface coating on lithium-ion battery cathodes improves their durability at high potentials, which is a well-known practical application. However, the mechanism is still unclear because the coating influences the electrode / electrolyte interface at a few nanometer-scale and direct observation of the interface under real operating conditions of a battery is challenging. This study reveals the mechanism of the surface coating effect on lithium-ion battery cathodes by using in operando X-ray absorption spectroscopy (XAS) on well-defined MgO-coated LiCoO2 thin-film electrodes prepared via pulsed laser deposition. Total-reflection in operando XAS measurements reveal that LiCoO2 forms a reductive phase at the interface between the uncoated-LiCoO2 electrode and the electrolyte, while the MgO coating layer inhibits the redox process, leading to an improvement in the cycle performance of the battery. Depth-resolved in operando XAS measurements indicate that a solid solution of the magnesium phase forms at the LiCoO2 surface upon MgO coating. Magnesium ions function as pillars to stabilize the layered structure at the interface between the LiCoO2 electrode and the electrolyte for delithiated states upon cycling at potentials., Dec. 2014, 1, 9, Scientific journal

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• Refereed, ELECTROCHEMISTRY, ELECTROCHEMICAL SOC JAPAN, Direct Observation of Rate Determining Step for Nd2NiO4+delta SOFC Cathode Reaction by operando Electrochemical XAS, Yuki Orikasa; Toshiaki Ina; Kentaro Yamamoto; Takayuki Nakao; Atsushi Mineshige; Koji Amezawa; Tatsuya Kawada; Hajime Tanida; Tomoya Uruga; Yoshiharu Uchimoto, The oxygen chemical potential of dense Nd2NiO4+delta thin films on Zr0.92Y0.08O1.96 electrolyte was investigated by operando X-ray absorption spectroscopy (XAS) measurements. Operando XAS at the Ni K-edge was measured under an applied voltage and various oxygen partial pressures at high temperature to simulate the operating conditions of solid oxide fuel cells (SOFCs). The absorption edge energy under various polarizations is similar to those measured under equivalent oxygen partial pressures under open circuit condition. Thus, the oxygen chemical potential changes drastically at the electrode/gas interface and the rate-determining step of this model system is the surface reaction. This study provides direct evidence for the rate-determining step of the SOFC cathode reaction. (C) The Electrochemical Society of Japan, All rights reserved., Oct. 2014, 82, 10, 897, 900, Scientific journal

  DOI
• Refereed, ELECTROCHEMISTRY, ELECTROCHEMICAL SOC JAPAN, Stabilization of the Electronic Structure at the Cathode/Electrolyte Interface via MgO Ultra-thin Layer during Lithium-ions Insertion/Extraction, Kentaro Yamamoto; Yuki Orikasa; Daiko Takamatsu; Yukinori Koyama; Shinichiro Mori; Titus Masese; Takuya Mori; Taketoshi Minato; Hajime Tanida; Tomoya Uruga; Zempachi Ogumi; Yoshiharu Uchimoto, Degradation mechanism of surface coating effects at the cathode/electrolyte interface is investigated using thin-film model electrodes combined with operando X-ray absorption spectroscopy (XAS). MgO-coated LiCoO2 thin-film electrodes prepared via pulsed laser deposition at room temperature and high temperature are used as model systems. The MgO coating improves the durability of the cathode during high-potential cycling. Operando total reflection fluorescence XAS reveals that initial deterioration due to reduction of Co ions at the surface of the uncoated-LiCoO2 thin film upon electrolyte immersion is inhibited by the MgO coating. Operando depth-resolved XAS reveals that the MgO coating suppresses drastic distortions of local structure at the LiCoO2 surface as observed in the uncoated-LiCoO2 during charging process. The electronic and local structure changes at the electrode/electrolyte interface for two types of surface coating morphologies are discussed. (C) The Electrochemical Society of Japan, All rights reserved., Oct. 2014, 82, 10, 891, 896, Scientific journal

  DOI
• Refereed, SOLID STATE IONICS, ELSEVIER SCIENCE BV, Local structural change in Li2FeSiO4 polyanion cathode material during initial cycling, Titus Masese; Yuki Orikasa; Takuya Mori; Kentaro p Yamamoto; Toshiaki Ina; Taketoshi Minato; Koji Nakanishi; Toshiaki Ohta; Cedric Tassel; Yoji Kobayashi; Hiroshi Kageyama; Hajime Arai; Zempachi Ogumi; Yoshiharu Uchimoto, To elucidate the Li+ extraction and insertion mechanism for Li2FeSiO4 nanoparticles, at the atomic scale, X-ray absorption spectroscopy (XAS) measurements at Fe and Si K-edges were performed. Fe K-edge XAS spectra suggest irreversible changes occurring in the local and electronic environment of iron which can be attributable to the characteristic shift in potential plateau during initial cycling of Li2 - xFeSiO4 system. While the local environment around Fe atoms significantly changes upon initial cycling, the local Si-O environment is mostly maintained. (C) 2013 Elsevier B.V. All rights reserved., Sep. 2014, 262, 110, 114, Scientific journal

  DOI
• Refereed, SCIENTIFIC REPORTS, NATURE PUBLISHING GROUP, High energy density rechargeable magnesium battery using earth-abundant and non-toxic elements, Yuki Orikasa; Titus Masese; Yukinori Koyama; Takuya Mori; Masashi Hattori; Kentaro Yamamoto; Tetsuya Okado; Zhen-Dong Huang; Taketoshi Minato; Cedric Tassel; Jungeun Kim; Yoji Kobayashi; Takeshi Abe; Hiroshi Kageyama; Yoshiharu Uchimoto, Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 mAh? g21 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de) insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl) imide-triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems., Jul. 2014, 4, Scientific journal

  DOI
• Refereed, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, Improved Cyclic Performance of Lithium-Ion Batteries: An Investigation of Cathode/Electrolyte Interface via In Situ Total-Reflection Fluorescence X-ray Absorption Spectroscopy, Kentaro Yamamoto; Taketoshi Minato; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Hajime Tanida; Koji Nakanishi; Haruno Murayama; Titus Masese; Takuya Mori; Hajime Arai; Yukinori Koyama; Zempachi Ogumi; Yoshiharu Uchimoto, For the further development of lithium-ion batteries, improvement of their cyclic performance is crucial. However, the mechanism underlying the deterioration of the battery cyclic performance is not fully understood. We investigated the effects of the electronic structure at the electrode/electrolyte interface on the cyclic performance of the cathode materials via in situ total-reflection fluorescence X-ray absorption spectroscopy. In a LiCoO2 thin-film electrode that exhibits gradual deterioration upon subsequent Li ion extractions and insertions (cycling), the reduction of Co ions at the electrode/electrolyte interface was observed upon immersion in an organic electrolyte, with subsequent irreversible changes after cycling. In contrast, in a LiFePO4 thin-film electrode, the electronic structure at the electrode/electrolyte interface was stable and reversible upon electrolyte immersion with subsequent cycling. The increased stability of the electronic structure at the LiFePO4/electrolyte interface affects its cycling performance., May 2014, 118, 18, 9538, 9543, Scientific journal

  DOI
• Refereed, CHEMISTRY OF MATERIALS, AMER CHEMICAL SOC, Relationship between Phase Transition Involving Cationic Exchange and Charge-Discharge Rate in Li2FeSiO4, Titus Masese; Yuki Orikasa; Cedric Tassel; Jungeun Kim; Taketoshi Minato; Hajime Arai; Takuya Mori; Kentaro Yamamoto; Yoji Kobayashi; Hiroshi Kageyama; Zempachi Ogumi; Yoshiharu Uchimoto, Li2FeSiO4 is considered a promising cathode material theoretical capacity and low cost. Li2FeSiO4, exhibits complex polymorphism and undergoes significant phase transformations during charge and discharge reaction. To elucidate the phase transformation mechanism, crystal structural changes during: charge and discharge processes of Li2FeSiO4 at different rates were investigated by X-ray diffraction measurements. The C/50 rate of lithium extraction upon initial cycling leads to a complete transformation from a monoclinic Li2FeSiO4 to a thermodynamically stable orthorhombic LiFeSiO4, concomitant with the occurrence of significant Li/Fe antisite mixing. The C/10 rate of lithium extraction and insertion, however, leads to retention of the parent Li2FeSiO4 (with the monoclinic structure as a metastable phase) with little cationic mixing. Here, we experimentally show the presence of metastable and stable LiFeSiO4 polymorphic phases caused by lithium extraction and insertion., Feb. 2014, 26, 3, 1380, 1384, Scientific journal

  DOI
• Refereed, CHEMISTRY-A EUROPEAN JOURNAL, WILEY-V C H VERLAG GMBH, Reversible Pore Size Control of Elastic Microporous Material by Mechanical Force, Masashi Ito; Hirotomo Nishihara; Kentaro Yamamoto; Hiroyuki Itoi; Hideki Tanaka; Akira Maki; Minoru T. Miyahara; Seung Jae Yang; Chong Rae Park; Takashi Kyotani, Nanoporous materials, such as zeolites, activated carbons, and metal-organic frameworks (MOFs), are peculiar platforms in which a variety of guest molecules are stored, reacted, and/or separated. The size of the nanopores is essential to realize advanced functions. In this work, we demonstrate a very simple but innovative method for the control of nanopore size, that is, reversible and continuous control by mechanical force loaded to soft nanoporous materials. The elastic properties of several microporous materials, including zeolites, zeolite-templated carbon (ZTC), activated carbon, and MOFs (e.g., ZIF-8), are examined and it is found that ZTC is a material that is suitable for the aforementioned idea thanks to its extraordinary soft properties compared to the others. The original pore size of ZTC (1.2nm) can be contracted to 0.85nm by using a relatively weak loading force of 135MPa, whereas the other microporous materials barely contracted. To demonstrate the change in the physical properties induced by such artificial deformation, in situ gas adsorption measurements were performed on ZTC with and without loading mechanical force, by using CO2, CH4, and H-2, as adsorbates. Upon the contraction by loading 69 or 135MPa, CO2 adsorption amount is increased, due to the deepening of the physisorption potential well inside the micropores, as proved by the increase of the heat of adsorption. Moreover, the adsorption amount is completely restored to the original one after releasing the mechanical force, indicating the fully reversible contraction/recovery of the ZTC framework against mechanical force. The experimental results are theoretically supported by a simulation using Grand Canonical Monte Carlo method. The similar adsorption enhancement is observed also on CH4, whereas H-2 is found as an exception due to the weak interaction potential., Sep. 2013, 19, 39, 13009, 13016, Scientific journal

  DOI
• Refereed, RSC ADVANCES, ROYAL SOC CHEMISTRY, A novel cationic-ordering fluoro-polyanionic cathode LiV0.5Fe0.5PO4F and its single phase Li+ insertion/extraction behaviour, Zhen-Dong Huang; Yuki Orikasa; Titus Masese; Kentaro Yamamoto; Takuya Mori; Taketoshi Minato; Yoshiharu Uchimoto, A novel fluoro-polyanionic cathode LiV0.5Fe0.5PO4F is synthesized via a wet ball-milling-assisted solid state method. Cationic ordering of V3+ and Fe3+ results in a single phase behaviour over the lithium composition range of Li1 +/- xV0.5Fe0.5PO4F (0 < x < 0.5) as revealed by X-ray diffraction analysis and electrochemical tests. This finding offers a versatile strategy of introducing single-phase behaviour in promising fluoro-polyanionic compounds exhibiting two-phase mechanisms., 2013, 3, 45, 22935, 22939, Scientific journal

  DOI
• Refereed, Chemistry of Materials, American Chemical Society (ACS), Na₃H(ZnH₄) Antiperovskite: A Large Octahedral Distortion with an Off-Centering Hydride Anion Coupled to Molecular Hydride, Shenghan Gao; Cédric Tassel; Susumu Fujii; Hiroki Ubukata; Tong Zhu; Datong Zhang; Thibault Broux; Takashi Saito; Chengchao Zhong; Emre Yoruk; Kentaro Yamamoto; Akihide Kuwabara; Yoshiharu Uchimoto; Hiroshi Kageyama, 25 Jul. 2022, Scientific journal

  DOI
• Refereed, Chemistry of Materials, American Chemical Society (ACS), Oxyfluoride Cathode for All-Solid-State Fluoride-Ion Batteries with Small Volume Change Using Three-Dimensional Diffusion Paths, Yanchang Wang; Tsuyoshi Takami; Zhuoran Li; Kentaro Yamamoto; Toshiyuki Matsunaga; Tomoki Uchiyama; Toshiki Watanabe; Hidenori Miki; Toshihiko Inoue; Hideki Iba; Uichiro Mizutani; Hirokazu Sato; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, 14 Nov. 2022, Scientific journal

  DOI
• Refereed, Electrochemistry, The Electrochemical Society of Japan, Properties of Composite Electrodes for All-solid-state Fluoride-ion Secondary Batteries Processed by High-pressure Torsion, Yanchang WANG; Sangmin LEE; Kentaro YAMAMOTO; Toshiyuki MATSUNAGA; Hidenori MIKI; Hideki IBA; Koichi TSUCHIYA; Tomoki UCHIYAMA; Toshiki WATANABE; Tsuyoshi TAKAMI; Yoshiharu UCHIMOTO, 2023, Scientific journal

  DOI
• Refereed, Chemistry of Materials, American Chemical Society (ACS), Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-Doped Barium Zirconates at Elevated Temperatures: In Situ X-ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations, Kenta Hoshino; Shusuke Kasamatsu; Junji Hyodo; Kentaro Yamamoto; Hiroyuki Setoyama; Toshihiro Okajima; Yoshihiro Yamazaki, 14 Mar. 2023, Scientific journal

  DOI

MISC

• Not Refereed, 機能材料, シーエムシー出版, フッ化物全固体電池, 山本 健太郎; 内本 喜晴, Jun. 2020, 40, 6, 1, 7
• Not Refereed, 電気化学, 測定法講座 リチウムイオン二次電池における放射光を用いたその場測定法, 折笠有基, 山本 健太郎, 内本喜晴, 2019, 87, 夏, 154, 164
• 電池討論会講演要旨集, Nafion/electrode interfacial structure analyzed via operando grazing incidence X-ray scattering spectroscopy and X-ray absorption spectroscopy, GAO Xiao; 高橋勝国; LIU Chen; 山本健太郎; 内山智貴; 中本康介; 谷田肇; 高尾直樹; 松本匡史; 今井英人; 与儀千尋; 横山浩司; 菅原生豊; 篠原和彦; 大木真里亜; 内本喜晴, 2017, 58th
• 電池討論会講演要旨集, High-energy XRD, XAFS and TEM analysis of Pt/C cathode catalyst in degraded MEA, 高橋勝國; 尾原幸治; 内山智貴; 中本康介; 山本健太郎; 谷田肇; 今井英人; 横山浩司; 大木真里亜; 菅原生豊; 篠原和彦; 内本喜晴, 2017, 58th
• 電池討論会講演要旨集, Temperature dependence on oxygen reduction reaction for carbon-supported Pd-core/Pt-shell electrocatalysts, LIU Chen; 内山智貴; 中本康介; 山本健太郎; 谷田肇; 高尾直樹; 今井英人; 横山浩司; 菅原生豊; 篠原和彦; 内本喜晴, 2017, 58th
• 電解技術討論会(ソーダ工業技術討論会)講演要旨集, 白金触媒の高エネルギーX線回折を用いた二体相関関数解析, 高橋勝國; 尾原幸治; 内山智貴; 山本健太郎; 谷田肇; 今井英人; 横山浩司; 大木真里亜; 菅原生豊; 篠原和彦; 内本喜晴, 2017, 41st
• 電解技術討論会(ソーダ工業技術討論会)講演要旨集, Pt/CおよびPt/Pd/Cコアシェル触媒上における酸素還元反応の温度依存性, 内山智貴; LIU Chen; 堀江悠希; 高裕太郎; 高橋勝國; 山本健太郎; 谷田肇; 高尾直樹; 今井英人; 横山浩司; 菅原生豊; 篠原和彦; 内本喜晴, 2017, 41st
• Not Refereed, X線分析の進歩, Development of in situ Soft X-Ray Absorption Spectroscopy Technique for Light Element Analysis in Lithium Ion Secondary Batteries, 中西康次; 中西康次; 谷田肇; 小松秀行; 小松秀行; 高橋伊久磨; 高橋伊久磨; 為則雄祐; 鶴田一樹; 家路豊成; 吉村真史; 山中恵介; 菊崎将太; 折笠有基; 折笠有基; 小島一男; 山本健太郎; 内本喜晴; 小久見善八; 太田俊明, 2017, 48, 403, 416
• 電気化学会大会講演要旨集(CD-ROM), オペランド軟X線吸収分光法によるマグネシウム二次電池負極の電極・電解質界面における反応機構解析, 服部将司; 山本健太郎; 森拓弥; 折笠有基; 中西康次; 谷田肇; 下田景二; 森正弘; 小山幸典; 為則雄祐; 内本喜晴, 2016, 83rd
• 電池討論会講演要旨集, in situ軟X線吸収分光法を用いたイオノマー/電極界面挙動解析, GAO X.; LIU C.; 山本健太郎; 谷田肇; 高尾直樹; 松本匡史; 今井英人; 与儀千尋; 横山浩司; 菅原生豊; 篠原和彦; 大木真里亜; 内本喜晴, 2016, 57th
• 電池討論会講演要旨集, オペランドX線吸収分光法を用いたPt/C触媒における酸素還元活性の温度依存性評価, 堀江悠希; 植元晶; 山本健太郎; 折笠有基; 谷田肇; 高尾直樹; 松本匡史; 今井英人; 横山浩司; 菅原生豊; 篠原和彦; 内本喜晴, 2016, 57th
• 電池討論会講演要旨集, 放射光X線回折を用いたPt/C触媒の劣化解析, 高橋勝國; 尾原幸治; 山本健太郎; 折笠有基; 谷田肇; 今井英人; 横山浩司; 大木真里亜; 菅原生豊; 篠原和彦; 内本喜晴, 2016, 57th
• 電池討論会講演要旨集, その場軟X線吸収分光法を用いたマグネシウム二次電池負極の反応支配因子解明, 服部将司; 山本健太郎; 森拓弥; 折笠有基; 中西康次; 谷田肇; 下田景二; 森正弘; 小山幸典; 為則雄祐; 小久見善八; 内本喜晴, 2015, 56th
• 触媒討論会討論会A予稿集(CD-ROM), 燃料電池用Pt触媒の酸素還元活性におけるアイオノマーの影響, 内山智貴; 劉辰; 山本健太郎; 渡辺稔樹; 松永利之; 片山翔太; 菅原生豊; 篠原和彦; 今井英人; 内本喜晴, 2020, 126th
• 触媒討論会討論会A予稿集(CD-ROM), コア粒径の異なるPt-Pdコアシェル触媒における酸素還元活性の温度依存性, 内山智貴; 劉辰; 山本健太郎; 渡辺稔樹; 松永利之; 片山翔太; 菅原生豊; 篠原和彦; 今井英人; 内本喜晴, 2020, 126th
• 電池討論会PDF要旨集(CD-ROM), Effect of the water/alcohol ratio of the dispersion on morphology and proton transport cast Nafion thin films on Pt electrodes, 山本健太郎; GAO Xiao; 平井智康; 太田昇; 内山智貴; 渡邊稔樹; 今井英人; 菅原生豊; 篠原和彦; 内本喜晴, 2020, 61st
• 電池討論会PDF要旨集(CD-ROM), The correlation between proton conductivity and morphology of Nafion thin-film on Pt electrode, GAO Xiao; 山本健太郎; 平井智康; 内山智貴; 高尾直樹; 片山翔太; 今井英人; 菅原生豊; 篠原和彦; 松永利之; 内本喜晴, 2019, 60th
• 電池討論会PDF要旨集(CD-ROM), The influence of usage amount of ionomer towards to the ORR activity of Pt/C catalyst, LIU Chen; 内山智貴; 山本健太郎; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 2019, 60th
• 電解技術討論会(ソーダ工業技術討論会)講演要旨集, The correlation between proton conductivity and morphology of Nafion thin-film on Pt electrode in polymer electrolyte fuel cells, GAO Xiao; 山本健太郎; 平井智康; 内山智貴; 高尾直樹; 片山翔太; 今井英人; 菅原生豊; 篠原和彦; 松永利之; 内本喜晴, 2019, 43rd
• 触媒討論会討論会A予稿集, Pd-core/Pt-shell触媒上での酸素還元反応の温度依存性, 山内智貴; 長田憲幸; 堀江悠希; 山本健太郎; 高尾直樹; 今井英人; 横山浩司; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 122nd
• 触媒討論会討論会A予稿集, ORR触媒活性に対する酸素被覆率及びNafion度が与える影響, 長田憲幸; 堀江悠希; 内山智貴; 山本健太郎; 高尾直樹; 今井英人; 横山浩司; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 122nd
• 電解技術討論会(ソーダ工業技術討論会)講演要旨集, Pt/C触媒の酸素被覆率及びアイオノマーが酸素還元活性に与える影響の解明, 長田憲幸; 内山智貴; 山本健太郎; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 42nd
• 電解技術討論会(ソーダ工業技術討論会)講演要旨集, Operando XAS用いたPt-Pd/Cコアシェル触媒ORR活性温度依存性の粒径影響, LIU Chen; 内山智貴; 堀江悠希; 山本健太郎; 高尾直樹; 今井英人; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 42nd
• 電池討論会講演要旨集, Elucidation of the effect of oxygen coverage and ionomer on ORR activity of Pt/C catalyst, 長田憲幸; 内山智貴; 山本健太郎; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 59th
• 電池討論会講演要旨集, Temperature dependence on oxygen reduction reaction for carbon-supported Pd-core/Pt-shell nanopartical electrocatalysts with different partical size, LIU Chen; 内山智貴; 山本健太郎; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 59th
• 電池討論会講演要旨集, Correlation between morphology and proton conductivity in Nafion thin-film with various thicknesses., GAO Xiao; 山本健太郎; 平井智康; 内山智貴; 高尾直樹; 片山翔太; 今井英人; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 59th
• ポーラログラフィーおよび電気分析化学討論会講演要旨集(Web), Pt/Pd/Cコアシェル触媒上における酸素還元活性の温度依存性評価, 山本健太郎; 劉辰; 内山智貴; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 2018, 64th
• 電池討論会PDF要旨集(CD-ROM), Elucidation of reaction mechanism of Li₂S-V₂S₃-LiI binary functional cathode for all-solid-state batteries, 渡邊稔樹; XIAO Yao; 山本健太郎; PAN Wenli; 内山智貴; 上杉健太朗; 竹内晃久; 作田敦; 林晃敏; 辰巳砂昌弘; 高見剛; 松永利之; 内本喜晴, 2021, 62nd
• 固体イオニクス討論会講演要旨集, Effect of properties of solvents used for liquid phase synthesis to lithium ion conductivity, 高橋勝國; 高橋勝國; YANG Seunghoon; 山本健太郎; 尾原幸治; 渡邊稔樹; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 引間和浩; 武藤浩行; 松田厚範; 内本喜晴, 2020, 46th (CD-ROM)
• 電池討論会PDF要旨集(CD-ROM), Effect of annealing conditions to the local structure and the lithium ion conductivity of Li₂S-P₂S₅-based electrolytes synthesized by using ethyl propionate, 高橋勝國; YANG Seunghoon; 山本健太郎; 尾原幸治; 渡邊稔樹; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 引間和浩; 武藤浩行; 松田厚範; 内本喜晴, 2020, 61st
• 電池討論会PDF要旨集(CD-ROM), Solvent effect on local structure and lithium ion conductivity of liquid phase synthesized Li₂S-P₂S₅-based electrolytes, 山本健太郎; YANG Seunghoon; 高橋勝國; 尾原幸治; 渡邊俊樹; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 引間和浩; 武藤浩行; 松田厚範; 内本喜晴, 2020, 61st
• 電気化学会大会講演要旨集(CD-ROM), 液相場で合成したLi₂S-P₂S₅系固体電解質の構造とイオン伝導度との関係, 高橋勝國; 山本健太郎; PHUC Nguyen Huu Huy; 尾原幸治; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 武藤浩行; 松田厚範; 内本喜晴, 2019, 86th
• 固体イオニクス討論会講演要旨集, PDF解析を用いた液相合成Li₂S-P₂S₅系固体電解質の局所構造とリチウムイオン伝導度の相関関係の解明, 高橋勝國; 高橋勝國; YANG Seunghoon; 山本健太郎; PHUC Nguyen Huu Huy; 尾原幸治; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 武藤浩行; 松田厚範; 松永利之; 内本喜晴, 2019, 45th
• 電池討論会PDF要旨集(CD-ROM), Suppression of Li metal dendrite growth by interfacial modification between Li metal anode/solid electrolyte, MU Zhiwei; 高橋勝國; XIAO Yao; 鈴木宏睦; 山本健太郎; 内山智貴; 上杉健太朗; 竹内晃久; 作田敦; 林晃敏; 辰巳砂昌弘; 松永利之; 内本喜晴, 2019, 60th
• 電池討論会PDF要旨集(CD-ROM), Direct observation of Li metal dendrite growth in all-solid-state batteries by operando CT measurement, MU Zhiwei; 高橋勝國; XIAO Yao; 鈴木宏睦; 山本健太郎; 内山智貴; 上杉健太朗; 竹内晃久; 作田敦; 林晃敏; 辰巳砂昌弘; 松永利之; 内本喜晴, 2019, 60th
• 電池討論会PDF要旨集(CD-ROM), Relationship between the local structure and lithium ionic conductivity of Li₂S-P₂S₅ solid electrolyte by pair distribution function analysis, 高橋勝國; YANG Seunghoon; 山本健太郎; PHUC Nguyen Huu Huy; 尾原幸治; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 武藤浩行; 松田厚範; 松永利之; 内本喜晴, 2019, 60th
• 固体イオニクス討論会講演要旨集, 高エネルギーX線回折を用いたLi₂S-P₂S₅固体電解質の液相合成機構解明, 高橋勝國; 山本健太郎; PHUC Nguyen Huu Huy; 尾原幸治; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 武藤浩行; 松田厚範; 内本喜晴, 2018, 44th
• 固体イオニクス討論会講演要旨集, Li₂RuO₃-Li₂SO₄系正極活物質を用いた全固体電池の充放電反応機構, 長尾賢治; 作田敦; 林晃敏; 塚崎裕文; 森茂生; 折笠有基; 山本健太郎; 内本喜晴; 辰巳砂昌弘, 2018, 44th
• 電池討論会講演要旨集, Mechanism analysis of liquid phase synthesis of Li₂S-P₂S₅ solid electrolyte by high energy X-ray diffraction measurement, 高橋勝國; 山本健太郎; PHUC Nguyen Huu Huy; 尾原幸治; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 武藤浩行; 松田厚範; 内本喜晴, 2018, 59th
• 固体イオニクス討論会講演要旨集, 二次元X線吸収分光法を用いた全固体リチウムイオン二次電池の電極内反応分布観察, CHEN Kezheng; 作田敦; 山本健太郎; 新庄紗枝; 倉谷健太郎; 竹内友成; 林晃敏; 辰巳砂昌弘; 木村勇太; 中村崇司; 雨澤浩史; 内本喜晴, 2017, 43rd
• 電池討論会講演要旨集, オペランド二次元X線吸収分光法を用いた全固体硫化物型リチウム二次電池における反応分布解析, 新庄紗枝; 作田敦; 折笠有基; CHEN K.; 森拓弥; 山本健太郎; 倉谷健太郎; 竹内友成; 林晃敏; 辰巳砂昌弘; 木村勇太; 中村崇司; 雨澤浩史; 内本喜晴, 2016, 57th

Books etc

• 複合アニオン化合物の科学, 丸善出版, 稲熊宜之; 内本喜晴; 荻野拓; 越智正之; 垣花眞人; 陰山洋; 北川俊作; 木本浩司; 桑原彰秀; 小林玄器; 小林亮; 設樂一希; 高津浩; 竹入史隆; 田部勢津久; 辻本吉廣; 長谷川哲也; 林克郎; 廣瀬靖; 本郷研太; 前園涼; 前田和彦; 鱒渕友治; 松石聡; 三上昌義; 八島正知; 山本健太郎; 山本隆文, 4.3節, 2021
• Next Generation Batteries: Realization of High Energy Density Rechargeable Batteries (English Edition) 1st ed., Springer Nature Singapore Pte Ltd., Chapter 15, XAFS Analysis, 2021
• 全固体リチウム電池の開発動向と応用展望, シーエムシー出版, 辰巳砂昌弘, 林晃敏, 鈴木耕太, 菅野了次, 宇都野太, 稲熊宜之, 濱本孝一, 浜尾尚樹, 藤代芳伸, 忠永清治, ナタリーカロリーナ ロゼロナバロ, 印田靖, 金相侖, 折茂慎一, 桑原彰秀, 森分博紀, 館山佳尚, 米村雅雄, 尾原幸治, 塩谷真也, 作田敦, 町田信也, 平山雅章, 太田鳴海, 本山宗主, 入山恭寿, 幸琢寛, 山本健太郎, 内本喜晴, 松田厚範, 仲村英也, 綿野哲, 櫻井芳昭, 長谷川泰則, 園村浩介, 佐藤和郎, 村上修一, 金村聖志, 奥村豊旗, 竹内友成, 是津信行, 手嶋勝弥, 猪石篤, 岡田重人, 伊藤大悟, 川村知栄, 秋本順二, 片岡邦光, 西尾和記, 一杉太郎, 佐々木俊介, 188 - 198, 2019

Presentations

• Kentaro Yamamoto; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Taketoshi Minato; Titus Masese; Takuya Mori; Hajime Tanida; Hajime Arai; Ogumi Zempachi; Uchimoto Yoshiharu, The 7th Asian Conference on Electrochemical Power Sources, ELECTRONIC STRUCTURE AT ELECTRODE/ELECTROLYTE INTERFACE OF LiFePO4 AND LiCoO2, 24 Nov. 2013, 27 Nov. 2103
• Kentaro Yamamoto; Xiao Gao; Tomoyasu Hirai; Noboru Ohta; Tomoki Uchiyama; Toshiki Watanabe; Hideto Imai; Seiho Sugawara; Kazuhiko Shinohara; Yoshiharu Uchimoto, MATERIALS RESEARCH MEETING 2021, Effect of alcohol/water ratio in dispersion on proton transport and morphology of cast perfluorinated sulfonic acid ionomers thin films, 13 Dec. 2021, 16 Dec. 2021
• Kentaro Yamamoto; Yanchang Wang; Yuki Sakaguchi; Hisao Kiuchi; Toshiyuki Matsunaga; Koji Nakanishi; Tomoki Uchiyama; Toshiki Watanabe; Tsuyoshi Takami; Hidenori Miki; Hideki Iba; Kazuhiko Maeda; Yoshihisa Harada; Hiroshi Kageyama; Yoshiharu Uchimoto, International Conference on Mixed-Anion Compounds, Electrochemical characterization and charge compensation mechanism of (Ca, Sr)FeO2 cathode with infinite layer structure, 07 Dec. 2021, 10 Dec. 2021
• Kentaro Yamamoto; Yao Xiao; Yukiko Matsui; Atsushi Sakuda; Koji Nakanishi; Tomoki Uchiyama; Toshiki Watanabe; Akitoshi Hayashi; Masahiro Tatsumisago; Masashi Ishikawa; Masayoshi Watanabe; Yoshiharu Uchimoto, International Conference on Lithium-Sulfur Batteries 2021, Clarification of reaction pathway difference of sulfur cathode between a concentrated liquid electrolyte and a solid-state electrolyte by soft X-way absorption spectroscopy, 28 Jun. 2021, 01 Jul. 2021
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Rina Yamamoto; Yuki Orikasa; Yoshiharu Uchimoto, Materials research meeting 2019, Direct Observation of Anion Redox in Li-excess Oxides with Different Covalent and Ionic Characters by operando Soft/Hard X-ray Absorption Spectroscopy, 10 Dec. 2019, 14 Dec. 2019
• Kentaro Yamamoto; Feilure Tuerxun; Masashi Hattori; Toshihiko Mandai; Ashu Choudhary; Yoshitaka Tateyama; Keitaro Sodeyama; Tomoki Uchiyama; Kiyoshi Kanamura; Yoshiharu Uchimoto, Lithium Battery Discussions 2019, Coordination Structure Effect between Magnesium Ions and Anion at Negative Electrode/Electrolyte Interface for Magnesium Alloying Reaction, 15 Sep. 2019, 20 Sep. 2019
• Kentaro Yamamoto; Aruto Watanabe; Tomoki Uchiyama; Akitoshi Hayashi; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, 22nd International Conference on Solid State Ionics, Controlled oxide ions redox on Li-excess metal oxides by nitrogen-doping, 16 Jun. 2019, 21 Jun. 2019
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Yuki Kobayashi; Rina Yamamoto; Yuki Orikasa; Toshiaki Ohta; Yoshiharu Uchimoto, Americas International Meeting on Electrochemistry and Solid State Science 2018, Charge compensation mechanism in Li-excess Oxides revealed by operando soft/hard X-ray absorption spectroscopy, 30 Sep. 2018, 04 Oct. 2018
• Kentaro Yamamoto; Takahiro Yoshinari; Eri Kato; Tomoki Uchiyama; Akihide Kuwabara; Kazuhiko Maeda; Hiroshi Kageyama; Yoshiharu Uchimoto, 16th Asian Conference on Solid State Ionics, Enhanced lithium ion transportation at the interface between LiFePO4 and electrolyte enhanced by surface-nitride treatment, 05 Aug. 2018, 09 Aug. 2018
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Yuki Kobayashi; Rina Yamamoto; Yuki Orikasa; Hye Ryung Byon; Toshiaki Ohta; Yoshiharu Uchimoto, 12th International Conference on Ceramic Materials and Components for Energy and Environmental Applications, Anion Redox Mechanism in Li-Excess Oxides with Different Ionic or Covalent Characters, 22 Jul. 2018, 27 Jul. 2018
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Yuki Kobayashi; Rina Yamamoto; Yuki Orikasa; Toshiaki Ohta; Yoshiharu Uchimoto, The 19th International Meeting on Lithium Batteries, Charge Compensation Mechanism in Li-Excess Oxides with Different Ionic or Covalent Characters, 17 Jun. 2018, 22 Jun. 2018
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Takahiro Yoshinari; Yuki Kobayashi; Rina Yamamoto; Aruto Watanabe; Jiwon Park; Hye Ryung Byon; Toshiaki Ohta; Yoshiharu Uchimoto, International Battery Association 2018, Charge Compensation Mechanism in Lithium-excess Metal Oxides with Different Ionic or Covalent Characters, 11 Mar. 2018, 16 Mar. 2018
• Kentaro Yamamoto; Naoaki Yabuuchi; Koji Nakanishi; Tomoki Uchiyama; Kosuke Nakamoto; Takahiro Yoshinari; Yuki Kobayashi; Rina Yamamoto; Aruto Watanabe; Jiwon. Park; Hye Ryung Byon; Toshiaki Ohta; Yoshiharu Uchimoto, 10th International Conference on Advanced Lithium Batteries for Automobile Applications, Anion Redox in Lithium-Excess Metal Oxides with different ionic or covalent characters, 22 Oct. 2017, 25 Oct. 2017
• Kentaro Yamamoto; Koji Nakanishi; Naoaki Yabuuchi; Takahiro Yoshinari; Takanori Kobayashi; Yuki Kobayashi; Rina Yamamoto; Aruto Watanabe; Keisuke Yamanaka; Jiwon Park; Hye Ryung Byon; Yuki Orikasa; Yusuke Tamenori; Toshiaki Ohta; Yoshiharu Uchimoto, Lithium Battery Discussions 2017, Charge compensation mechanism in lithium-rich cathode materials with different ionic or covalent character, 11 Jun. 2017, 16 Jun. 2017
• Kentaro Yamamoto; Taketoshi Minato; Yuki Orikasa; Daiko Takamatsu; Titus Masese; Takuya Mori; Hajime Tanida; Zempachi Ogumi; Yoshiharu Uchimoto, 7th International Conference on Advanced Lithium Batteries for Automobile Applications, in operando XAFS study on electrode/electrolyte interface in LiFePO4 and LiCoO2, 29 Jul. 2014, 01 Aug. 2014
• Kentaro Yamamoto; Taketoshi Minato; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Hajime Tanida; Hajime Arai; Yukinori Koyama; Zempachi Ogumi; Yoshiharu Uchimoto, The 17th International Meeting on Lithium Batteries, Correlation between the electronic structure at electrode/electrolyte interface and durability in lithium-ion batteries, 10 Jun. 2014, 14 Jun. 2014
• Kentaro Yamamoto; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Taketoshi Minato; Hajime Tanida; Zempachi Ogumi; Yoshiharu Uchimoto, INTERNATIONAL BATTERY ASSOCIATION 2014, Investigation Of The Electronic Structure At Cathode/Electrolyte Interface In Lithium Ion Battery Via In-Situ Total-Reflection Fluorescence X-ray Absorption Spectroscopy, 03 Mar. 2014, 07 Mar. 2014
• Kentaro Yamamoto; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Taketoshi Minato; Hajime Tanida; Hajime Arai; Zempachi Ogumi; Yoshiharu Uchimoto, The 224th Meetings of ECS, Stability of the Electronic Structure at LiFePO4 Surface during Charge/Discharge Process, 27 Oct. 2013, 01 Nov. 2013
• Kentaro Yamamoto; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Taketoshi Minato; Hajime Tanida; Hajime Arai; Zempachi Ogumi; Yoshiharu Uchimoto, The 19th International Conference on Solid State Ionics, Reversible Change of the Electronic Structure of LiFePO4 surface during Charge/Discharge Process, 02 Jun. 2013, 07 Jun. 2013
• 山本健太郎; 王彦昌; 阪口祐紀; 木内久雄; 松永利之; 中西康次; 内山智貴; 渡邊稔樹; 高見剛; 三木秀教; 射場英紀; 前田和彦; 原田慈久; 陰山洋; 内本喜晴, 第47回固体イオニクス討論会, Infinite layer 構造を有する全固体フッ化物電池(Ca, Sr)FeO2正極のフッ化物イオン挿入脱離反応機構, 08 Dec. 2021, 10 Dec. 2021
• 山本健太郎; 梁勝勳; 渡邊稔樹; 三輪託也; 川合光幹; 内山智貴; 松永利之; 高見剛; 内本喜晴, 第62回電池討論会, operando X線CTを用いた全固体電池黒鉛負極上リチウムデンドライト成長の直接観察, 30 Nov. 2021, 02 Dec. 2021
• 山本健太郎; 張大同; 木内久雄; 中西康次; 内山智貴; 渡邊稔樹; 高見剛; 松永利之; 三木秀教; 井手一人; 射場英紀; 前田和彦; 原田慈久; 陰山洋; 内本喜晴, 第62回電池討論会, 全固体フッ化物二次電池Cu3N正極における電荷補償機構の解明, 30 Nov. 2021, 02 Dec. 2021
• 山本健太郎; 王彦昌; 阪口祐紀; 木内久雄; 松永利之; 中西康次; 内山智貴; 渡邊稔樹; 高見剛; 三木秀教; 射場英紀; 前田和彦; 原田慈久; 陰山洋; 内本喜晴, 第62回電池討論会, インターカレーション型フッ化物イオン電池用正極材料の開発9 Infinite layer構造を有する(Ca, Sr)FeO2正極の電気化学特性評価, 30 Nov. 2021, 02 Dec. 2021
• 山本健太郎; トウルソン フィロラ; 松永利之; 今井宏明; 万代俊彦; 渡邊稔樹; 内山智貴; 金村聖志; 内本喜晴, 第46回固体イオニクス討論会, マグネシウムイオン挿入時におけるMgMn2O4スピネル酸化物の相転移機構の解明, 08 Dec. 2020, 09 Dec. 2020
• 山本健太郎; 高橋勝國; 梁勝勳; 尾原幸治; 渡邊俊樹; 内山智貴; 作田敦; 林晃敏; 辰巳砂昌弘; 引間和浩; 武藤浩行; 松田厚範; 内本喜晴, 第61回電池討論会, 液相合成Li2S-P2S5固体電解質の局所構造とリチウムイオン伝導度に及ぼす溶媒の影響, 18 Nov. 2020, 20 Nov. 2020
• 山本健太郎; トウルソン フィロラ; 万代俊彦; 中西康次; 袖山慶太郎; 館山佳尚; 内山智貴; 松永利之; 金村聖志; 内本喜晴, 電気化学会第87回大会, Mg2+/アニオン静電相互作用を制御した電解液中でのMg金属析出反応機構の解明, 17 Mar. 2020, 19 Mar. 2020
• 山本健太郎; 矢原竜馬; 新田朔也; 田中健太; 内山智貴; 折笠有基; 雨澤浩史; 内本喜晴, 第59回電池討論会, 全固体フッ化物イオン電池における負極/固体電解質界面反応の速度論, 27 Nov. 2018, 29 Nov. 2018
• 山本健太郎; 劉辰; 内山智貴; 高尾直樹; 今井英人; 片山翔太; 菅原生豊; 篠原和彦; 内本喜晴, 第64回ポーラログラフィーおよび電気分析化学討論会, Pt/Pd/Cコアシェル触媒上における酸素還元 活性の温度依存性評価, 22 Nov. 2018, 23 Nov. 2018
• 山本健太郎; 矢原竜馬; 新田朔也; 内山智貴; 折笠有基; 雨澤浩史; 内本喜晴, 電気化学会第85回大会, 全固体フッ化物イオン電池における負極／固体電解質界面抵抗, 09 Mar. 2018, 11 Mar. 2018
• 山本健太郎; 藪内直明; 中西康次; 内山智貴; 山本梨乃; 小林佑輝; 吉成崇宏; 渡辺有人; J. Park; H. R. Byon; 太田俊明; 内本喜晴, 第43回固体イオニクス討論会, オペランド軟/硬X線吸収分光法を用いたLi過剰系正極酸素レドックス機構の解明, 05 Dec. 2017, 07 Dec. 2017
• 山本健太郎; 奥山勇治; 山崎仁丈, 日本金属学会2016年春期(第158回)大会, La0.6Sr0.4MnO3-δの酸素空孔を利用した熱化学二酸化炭素還元, 23 Mar. 2016, 25 Mar. 2106
• 山本健太郎; 服部将司; 内山智貴; 中本康介; 中西康次; 内本喜晴, 第41回電解技術討論会, マグネシウムイオンの還元に及ぼすアニオン種の影響, 21 Nov. 2017, 22 Nov. 2017
• 山本健太郎; 中西康次; 服部将司; 折笠有基; 為則雄祐; 内本喜晴, ポーラログラフィーおよび電気分析化学討論会, Mg(TFSA)2系電解質中におけるマグネシウム金属析出反応機構の解析, 20 Nov. 2017, 21 Nov. 2017
• 山本健太郎; 藪内直明; 中西康次; 中本康介; 内山智貴; 山本梨乃; 小林佑輝; 吉成崇宏; 渡辺有人; Jiwon Park; Hye Ryung Byon; 太田俊明; 内本喜晴, 第58回電池討論会, オペランド軟/硬X線吸収分光法を用いたLi過剰系正極酸素レドックス安定化機構の解明, 14 Nov. 2017, 16 Nov. 2017
• 山本健太郎; 加藤愛梨; 吉成崇宏; 折笠有基; 中西康次; 太田俊明; 内本喜晴, 電気化学会第84回大会, 表面窒化 LiFePO4正極/電解質界面における相転移反応機構の解明, 25 Mar. 2017, 27 Mar. 2017
• 山本健太郎; 加藤愛梨; 吉成崇宏; 折笠有基; 中西康次; 太田俊明; 内本喜晴, 2016年度 固体化学の新しい指針を探る研究会 若手による発表の会, 表面窒化LiFePO4正極/電解質界面における相転移挙動, 03 Mar. 2017, 03 Mar. 2017
• 山本健太郎; 中西康次; 藪内直明; 吉成崇宏; 山本梨乃; 渡辺有人; 山中恵介; 折笠有基; 為則雄祐; 太田俊明; 内本喜晴, 第42回固体イオニクス討論会, オペランド軟X 線吸収分光法を用いたLi 過剰系正極の電荷補償機構解明, 05 Dec. 2016, 07 Dec. 2016
• 山本健太郎; 奥山勇治; 山崎仁丈, 第41回固体イオニクス討論会, La0.6Sr0.4MnO3-δにおける熱化学CO2還元能の評価と反応速度制御, 25 Nov. 2015, 27 Nov. 2015
• 山本健太郎; S. Wilke; S. M. Haile; 山崎仁丈, 2015年第157回秋期講演大会, Ga置換La0.8Sr0.2MnO3-δにおける熱化学水分解特性の評価, 16 Sep. 2015, 18 Sep. 2015
• Kentaro Yamamoto; Daiko Takamatsu; Yuki Orikasa; Hajime Tanida; Zempachi Ogumi; Yoshiharu Uchimoto, The 55th Battery Symposium in Japan, Operando X-ray Absorption Spectroscopic Study on Electrode / Electrolyte Interface, 19 Nov. 2014, 21 Nov. 2014
• 山本健太郎; マセセタイタス; 森拓弥; 折笠有基; 内本喜晴, 第55回電池討論会, オリビン型正極FePO4のマグネシウム挿入脱離挙動, 19 Nov. 2014, 21 Nov. 2014
• 山本健太郎; 湊丈俊; 折笠有基; 高松大郊; 小山幸典; 谷田肇; 小久見善八; 内本喜晴, 電気化学会第81回大会, リチウムイオン電池電極・電解質界面構造と劣化機構, 29 Mar. 2014, 31 Mar. 2014
• 山本健太郎, 電気化学会第89回大会, 放射光X線を用いた高度解析による電子論的設計指針に基づく電極材料の創生, 15 Mar. 2022, 17 Mar. 2022
• 山本健太郎, 2021年度第2回関西電気化学研究会Webinar, 固体内アニオンの特異な電子構造制御に基づいた二次電池正極材料の設計, 30 Sep. 2021, 30 Sep. 2021
• 山本健太郎; 藪内直明; 中西康; 中本康介; 内山智貴; 山本梨乃; 小林佑輝; 吉成崇宏; 渡辺有人; 太田俊明; 内本喜晴, 第13回固体イオニクスセミナー, オペランド軟/硬X線吸収分光法を用いたLi過剰系正極アニオンレドックス機構の解明, 12 Sep. 2017, 14 Sep. 2017
• 山本健太郎; 加藤愛梨; 吉成崇宏; 折笠有基; 中西康次; 太田俊明; 内本喜晴, 第6回JACI/GSCシンポジウム, 表面窒化LiFePO4正極/電解質界面における相転移反応機構, 03 Jul. 2017, 04 Jul. 2017
• 山本健太郎; 瀬戸山寛之; 奥山勇治; 岡本敏浩; 山崎仁丈, 第11回固体イオニクスセミナー, 熱化学水分解におけるLa1-xSrxMnO3-δ酸化還元反応の評価, 30 Aug. 2015, 01 Sep. 2015
• Kentaro Yamamoto; Taketoshi Minato; Shinichiro Mori; Daiko Takamatsu; Yuki Orikasa; Hajime Tanida; Hajime Arai; Yukinori Koyama; Zempachi Ogumi; Yoshiharu Uchimoto, The 10th Japan-France Joint Seminar on Battery, Clarification of the Electronic Structure at LiCoO2 and LiFePO4/Electrolyte Interface via In-operando Total Reflection Fluorescence X-ray Absorption Spectroscopy, 22 Sep. 2014, 24 Sep. 2014
• 山本健太郎; マセセタイタス; 森拓弥; 折笠有基; 内本喜晴, 第10回固体イオニクスセミナー, オリビン型FePO4におけるMg2+挿入脱離反応機構の解明, 31 Aug. 2014, 02 Sep. 2014
• 山本健太郎; 湊丈俊; 折笠有基; 高松大郊; 小山幸典; 森伸一郎; 谷田肇; 小久見善八; 内本喜晴, 固体化学の新しい指針を探る研究会 第74回定例研究会 若手研究者による研究発表会, In-situ XASを用いたリチウムイオン電池正極・電解液ヘテロ界面電子構造と劣化機構の解明, 12 Mar. 2014, 12 Mar. 2014
• 山本健太郎; 湊丈俊; 折笠有基; 高松大郊; 谷田肇; 小久見善八; 内本喜晴, 2013年度第3回関西電気化学研究会, リチウムイオン電池サイクル特性を支配する電極・電解液界面構造, 07 Dec. 2013, 07 Dec. 2013
• 山本健太郎; 高松大郊; 折笠有基; 湊丈俊; 谷田肇; 小久見善八; 内本喜晴, 第39回固体イオニクス討論会, X線吸収法を用いたLiCoO2およびLiFePO4薄膜電極・電解質モデル界面における電子構造その場観測, 20 Nov. 2013, 22 Nov. 2013
• 山本健太郎; マセセタイタス; 森拓弥; 折笠有基; 湊丈俊; 内本喜晴, 第54回電池討論会, Mgイオン挿入脱離反応に伴うFePO4の結晶構造変化と反応素過程, 07 Oct. 2013, 09 Oct. 2013
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 小山幸典; 湊丈俊; 谷田肇; 小久見善八; 内本喜晴, 第54回電池討論会, 放射光その場解析を用いたリチウムイオン電池正極／電解質界面構造の解析, 07 Oct. 2013, 09 Oct. 2013
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 小山幸典; 湊丈俊; 谷田肇; 小久見善八; 内本喜晴, 第9回固体イオニクスセミナー, 放射光その場測定を用いたリチウムイオン電池電極/電解質へテロ界面の電子構造解明, 08 Sep. 2013, 10 Sep. 2013
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 湊丈俊; 谷田肇; 荒井創; 小久見善八; 内本喜晴, 電気化学会第80周年記念大会, in-situ全反射XAFS測定を用いたリチウムイオン電池正極／電解液界面の電子構造解明, 29 Mar. 2013, 31 Mar. 2013
• 山本 健太郎; 森 伸一郎; 高松 大郊; 折笠 有基; 湊 丈俊; 谷田 肇; 荒井 創; 小久見 善八; 内本 喜晴, 固体化学の新しい指針を探る研究会 若手研究者による研究発表会, in-situ全反射蛍光XAS測定を用いたLiFePO4薄膜電極／有機電解液界面の電子構造解明, Mar. 2013, Mar. 2013
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 谷田肇; 宇留賀朋哉; 荒井創; 小久見善八; 内本喜晴, 第26回放射光学会年会, LiCoO2薄膜電極のin situ XAFS測定による表被覆効果メカニズムの解明, 12 Jan. 2013, 14 Jan. 2013
• 山本 健太郎; 森 伸一郎; 高松 大郊; 折笠 有基; 湊 丈俊; 谷田 肇; 小山 幸典; 宇留賀 朋哉; 荒井 創; 小久見 善八; 内本 喜晴, 第38回固体イオニクス討論会, in situ XAFS測定を用いたLiCoO2薄膜電極／有機電解液界面の反応機構解明, 03 Dec. 2012, 05 Dec. 2012
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 湊丈俊; 小山幸典; 谷田肇; 荒井創; 小久見善八; 内本喜晴, 2012年度第3回関西電気化学研究会, in situ XAFS測定を用いたリチウムイオン電池正極／有機電解液界面の反応機構解明, 01 Dec. 2012, 01 Dec. 2012
• 山本健太郎; 森伸一郎; 高松大郊; 折笠有基; 谷田肇; 宇留賀朋哉; 荒井創; 小久見善八; 内本喜晴, 第8回固体イオニクスセミナー, LiCoO2薄膜電極の電気化学およびXAFS測定による表面被覆効果メカニズムの解明, 02 Sep. 2012, 04 Sep. 2012
• 山本健太郎; 西原洋知; Somlak Ittisanronnachai; 伊藤仁; 内山誠; 京谷隆, 第11回多元物質科学研究所研究発表会, 規則性ミクロポーラスカーボンの可逆的な細孔径制御に伴うメタン吸着量の変化, 08 Dec. 2011, 08 Dec. 2011
• 山本健太郎; 西原洋知; Somlak Ittisanronnachai; 伊藤仁; 内山誠; 京谷隆, 第38回炭素材料学会年会, ゼオライト鋳型炭素の細孔径可逆制御に伴う分子吸着量の変化, 29 Nov. 2011, 01 Dec. 2011
• 山本健太郎; 西原洋知; 伊藤仁; 内山誠; 京谷隆, 第37回炭素材料学会年会, ゼオライト鋳型炭素の細孔径可逆制御とそれに伴うガス吸着特性変化, 01 Dec. 2010, 03 Dec. 2010
• 山本健太郎; 西原洋知; 京谷隆, 平成 22 年度化学系学協会東北大会, 機械的圧縮によるミクロポーラスカーボンの細孔径可逆制御, 25 Sep. 2010, 26 Sep. 2010
• Kentaro Yamamoto; Hirotomo Nishihara; Hiroyuki Itoi; Somlak Ittisanronnachai; Takashi Kyotani, 蔵王10研究会, Spring-like behavior of 3D graphene network, 20 Jul. 2010, 21 Jul. 2010
• 山本健太郎, 第61回セラミックス基礎科学討論会, 固体内アニオンの特異な電子状態制御に基づいた高容量正極材料の設計, 08 Jan. 2023
• 山本健太郎; 張大同; 木内久雄; 中西康次; 内山智貴; 渡邊稔樹; 高見剛; 松永利之; 三木秀教; 井手一人; 射場英紀; 前田和彦; 原田慈久; 陰山洋; 内本喜晴, 第48回固体イオニクス討論会, 全固体フッ化物二次電池Cu3N正極のフッ化物イオン挿入・脱離反応機構の解明, 08 Dec. 2022
• 山本健太郎; 邉見光紀; 渡邊稔樹; 佐野光; 中西康次; 内山智貴; 松永利之; 高見剛; 作田敦; 林晃敏; 辰巳砂昌弘; 川本浩二; 内本喜晴, 第63回電池討論会, in situ軟X線吸収分光法を用いた硫化物固体電解質の水蒸気劣化機構の解明, 09 Nov. 2022
• 山本健太郎; 渡邊稔樹; 尾原幸治; 内山智貴; 松永利之; 高見剛; 作田敦; 林晃敏; 辰巳砂昌弘; 内本喜晴, 第63回電池討論会, Li3PS4-Li4SnS4系ガラス固体電解質の局所構造とイオン伝導度との相関関係, 08 Nov. 2022
• 山本健太郎, 第53回中部化学関係学協会支部連合秋季大会, 固体内アニオンの特異な電子状態を活用した高容量二次電池正極の設計, 06 Nov. 2022
• 山本健太郎; 三木秀教; 内本喜晴, 第118回新電池構想部会講演会, 固体内アニオン分子形成を活用した全固体フッ化物イオン二次電池正極の開発, 07 Oct. 2022
• Kentaro Yamamoto; Yanchang Wang; Yuki Sakaguchi; Hisao Kiuchi; Toshiyuki Matsunaga; Koji Nakanishi; Tomoki Uchiyama; Toshiki Watanabe; Tsuyoshi Takami; Hidenori Miki; Hideki Iba; Kazuhiko Maeda; Yoshihisa Harada; Hiroshi Kageyama; Yoshiharu Uchimoto, The 21th International Meeting on Lithium Batteries, Electrochemical performance of (Ca, Sr)FeO2 cathode with infinite layer structure for all-solid-state fluoride ion battery, Jun. 2022
• 山本健太郎; 邉見光紀; 渡邊稔樹; 佐野光; 中西康次; 内山智貴; 松永利之; 高見剛; 作田敦; 林晃敏; 辰巳砂昌弘; 川本浩二; 内本喜晴, 電気化学会第90回大会, in situ軟X線吸収分光法を用いた全固体電池用硫化物固体電解質の水蒸気劣化機構解明, 28 Mar. 2023, 27 Mar. 2023, 29 Mar. 2023

Awards

• 2022年度電気化学会進歩賞（佐野賞）, 公益社団法人 電気化学会, Mar. 2022
• 平成25年度関西電気化学奨励賞, Dec. 2013
• The 7th Asian Conference on Electrochemical Power Sources, 1st Poster Prize, Nov. 2013
• 第38回炭素材料学会年会, ポスター賞, Nov. 2011
• 電池技術委員会賞, 電池技術委員会, Nov. 2022

Research Projects

• 01 Apr. 2021, 31 Mar. 2023
• 01 Apr. 2022, 31 Jul. 2022
• Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Apr. 2022, Mar. 2024, 22H04616, Studies on reaction layer at solid/solid interface by using operando X-ray reflectometry, 山本 健太郎, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kyoto University, 5200000, 4000000, 1200000
• 基盤研究(B), Apr. 2021, Mar. 2024, 21H02048, Principal investigator, 過剰なフッ化物イオンの挿入・脱離反応を利用した新規鉄系酸化物正極の創成, 山本 健太郎, 日本学術振興会, 科学研究費助成事業 基盤研究(B), 京都大学, 18070000, 13900000, 4170000
• 基盤研究(B), Apr. 2020, Mar. 2023, 20H02846, Coinvestigator, 酸素アニオン制御による新規電極反応を用いた高エネルギー密度正極材料の創造, 大石 昌嗣; 尾原 幸治; 山本 健太郎, 日本学術振興会, 科学研究費助成事業 基盤研究(B), 徳島大学, 18070000, 13900000, 4170000
• 新学術領域研究(研究領域提案型), Apr. 2020, Mar. 2022, 20H05294, Principal investigator, オペランドX線反射率法を用いた蓄電固体界面イオンダイナミクスの解明, 山本 健太郎, 日本学術振興会, 科学研究費助成事業 新学術領域研究(研究領域提案型), 京都大学, 3900000, 3000000, 900000
• Grant-in-Aid for Early-Career Scientists, Apr. 2018, Mar. 2020, 18K14322, Principal investigator, Improved interfacial reaction between cathode and aqueous electrolyte in lithium-ion secondary batteries based on electrolyte structure control, Yamamoto Kentaro, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists, Kyoto University, 4160000, 3200000, 960000, Lithium-ion secondary batteries using highly concentrated aqueous electrolytes exhibit high rate characteristics in spite of the low ionic conductivity of the electrolyte. However, the mechanism of this behavior is not clearly understood. The purpose of this study is to understand electrochemical parameter of the reaction at the interface between cathode and electrolyte in a highly concentrated aqueous lithium-ion battery. The cathode reaction was divided into lithium ion diffusion in the cathode, interfacial reaction between cathode and electrolyte by using a thin-film cathode, and lithium ion diffusion in the bulk electrolyte, and the electrolyte concentration dependency was evaluated for electrochemical parameters of each process. It was found that the frequency factor of lithium ion insertion/extraction reaction at the interface was significantly improved at high concentrations, resulting in the high rate performance., url

  対象リソースIRI

Ⅲ．社会連携活動実績

１．公的団体の委員等（審議会、国家試験委員、他大学評価委員，科研費審査委員等）

• Jan. 2019, 9999