Journal articles
2021 |
|
 | Takuya Hatakeyama, Hongyi Li, Norihiko L. Okamoto, Kohei Shimokawa, Tomoya Kawaguchi, Hiroshi Tanimura, Susumu Imashuku, Maximilian Fichtner, Tetsu Ichitsubo Accelerated Kinetics Revealing Metastable Pathways of Magnesiation-Induced Transformations in MnO2 Polymorphs Journal Article Chemistry of Materials, 33 (17), pp. 6983-6996, 2021. @article{Hatakeyama2021a, title = {Accelerated Kinetics Revealing Metastable Pathways of Magnesiation-Induced Transformations in MnO_{2} Polymorphs}, author = {Takuya Hatakeyama and Hongyi Li and Norihiko L. Okamoto and Kohei Shimokawa and Tomoya Kawaguchi and Hiroshi Tanimura and Susumu Imashuku and Maximilian Fichtner and Tetsu Ichitsubo}, url = {https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.1c02011}, doi = {https://doi.org/10.1021/acs.chemmater.1c02011}, year = {2021}, date = {2021-08-17}, journal = {Chemistry of Materials}, volume = {33}, number = {17}, pages = {6983-6996}, abstract = {The intrinsic potential of manganese dioxides, considered high-capacity cathodes of rechargeable magnesium batteries, was clearly exposed under conditions where the Mg migration kinetics are sufficiently enhanced. It has been reported to date that magnesium insertion into MnO_{2}is substantially confined to the surfaces of MnO_{2} particles due to its sluggish kinetics at room temperature, which leads to local overmagnesiation conditions causing conversion reactions etc. To unveil its ergodic or metastable phase-transformation pathways of MnO_{2} polymorphs (α, β, γ, δ, and λ) during magnesiation, this study employed intermediate-temperature electrochemical experiments (at 150 °C) using heat-tolerant ionic liquid electrolytes. Regardless of its original polymorphic structure, each MnO_{2}polymorph was found to transform into a Mg-including spinel and then to a rocksalt-like phase by magnesiation. Given this tendency of transformation, the defect spinel λ-MnO_{2}phase possessing the coherent framework of spinel/rocksalt structures is expected to follow a topotactic transformation pathway, but thermally unstable λ-MnO_{2}underwent spontaneous reduction into Mn_{3}O_{4} before magnesiation in an electrolyte. Instead, α-MnO_{2}was found to be robust enough among MnO_{2}polymorphs to exhibit reversible magnesium intercalation at 150 °C under limiting capacity conditions. This result highlights that reversible magnesium intercalation in oxide cathodes is feasible for structures that are kinetically resistant to irreversible transformation pathways to spinel and rocksalt structures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The intrinsic potential of manganese dioxides, considered high-capacity cathodes of rechargeable magnesium batteries, was clearly exposed under conditions where the Mg migration kinetics are sufficiently enhanced. It has been reported to date that magnesium insertion into MnO2is substantially confined to the surfaces of MnO2 particles due to its sluggish kinetics at room temperature, which leads to local overmagnesiation conditions causing conversion reactions etc. To unveil its ergodic or metastable phase-transformation pathways of MnO2 polymorphs (α, β, γ, δ, and λ) during magnesiation, this study employed intermediate-temperature electrochemical experiments (at 150 °C) using heat-tolerant ionic liquid electrolytes. Regardless of its original polymorphic structure, each MnO2polymorph was found to transform into a Mg-including spinel and then to a rocksalt-like phase by magnesiation. Given this tendency of transformation, the defect spinel λ-MnO2phase possessing the coherent framework of spinel/rocksalt structures is expected to follow a topotactic transformation pathway, but thermally unstable λ-MnO2underwent spontaneous reduction into Mn3O4 before magnesiation in an electrolyte. Instead, α-MnO2was found to be robust enough among MnO2polymorphs to exhibit reversible magnesium intercalation at 150 °C under limiting capacity conditions. This result highlights that reversible magnesium intercalation in oxide cathodes is feasible for structures that are kinetically resistant to irreversible transformation pathways to spinel and rocksalt structures. |
 | Kohei Shimokawa, Takuya Furuhashi, Tomoya Kawaguchi, Won-Young Park, Takeshi Wada, Hajime Matsumoto, Hidemi Katoa, Tetsu Ichitsubo Electrochemically Synthesized Liquid-Sulfur/Sulfide Composite Materials for High-rate Magnesium Battery Cathodes Journal Article Journal of Materials Chemistry A, 9 , pp. 16585-16593, 2021. @article{Shiomokawa2021a, title = {Electrochemically Synthesized Liquid-Sulfur/Sulfide Composite Materials for High-rate Magnesium Battery Cathodes}, author = {Kohei Shimokawa and Takuya Furuhashi and Tomoya Kawaguchi and Won-Young Park and Takeshi Wada and Hajime Matsumoto and Hidemi Katoa and Tetsu Ichitsubo}, url = {https://pubs.rsc.org/en/content/articlelanding/2021/ta/d1ta03464b}, doi = {https://doi.org/10.1039/D1TA03464B}, year = {2021}, date = {2021-07-26}, journal = {Journal of Materials Chemistry A}, volume = {9}, pages = {16585-16593}, abstract = {Mg/S batteries are some of the most promising rechargeable batteries owing to their high theoretical energy density. Their development is, however, hindered by (i) low electronic conductivity of S, (ii) sluggish Mg^{2+} diffusion in solid Mg–S compounds formed by discharge, and (iii) dissolubility of polysulfides into electrolytes. To address these problems, we propose liquid-S/sulfide composite cathode materials in combination with an ionic liquid electrolyte at intermediate temperatures (∼150 °C). The composite structure is spontaneously fabricated by electrochemically oxidizing metal sulfides, yielding liquid S embedded in a porous metal-sulfide conductive frame. This concept is demonstrated by a S/FeS_{2} composite cathode, which shows a significantly high-rate capability of, e.g., 1246 mA g^{−1}(S) with a capacity of ∼900 mA h g^{−1}(S). In addition, non-equilibrium liquid S formed by fast charging results in an unexpected higher discharge potential. This work provides a new strategy to design S-based cathodes for achieving high-rate multivalent rechargeable batteries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mg/S batteries are some of the most promising rechargeable batteries owing to their high theoretical energy density. Their development is, however, hindered by (i) low electronic conductivity of S, (ii) sluggish Mg2+ diffusion in solid Mg–S compounds formed by discharge, and (iii) dissolubility of polysulfides into electrolytes. To address these problems, we propose liquid-S/sulfide composite cathode materials in combination with an ionic liquid electrolyte at intermediate temperatures (∼150 °C). The composite structure is spontaneously fabricated by electrochemically oxidizing metal sulfides, yielding liquid S embedded in a porous metal-sulfide conductive frame. This concept is demonstrated by a S/FeS2 composite cathode, which shows a significantly high-rate capability of, e.g., 1246 mA g−1(S) with a capacity of ∼900 mA h g−1(S). In addition, non-equilibrium liquid S formed by fast charging results in an unexpected higher discharge potential. This work provides a new strategy to design S-based cathodes for achieving high-rate multivalent rechargeable batteries. |
 | Tomoya Kawaguchi, Vladimir Komanicky, Vitalii Latyshev, Wonsuk Cha, Evan Maxey, Ross Harder, Tetsu Ichitsubo, Hoydoo You Electrochemically Induced Strain Evolution in Pt-Ni Alloy Nanoparticles Observed by Bragg Coherent Diffraction Imaging Journal Article Nano Letters, 21 (14), pp. 5945–5951, 2021. @article{Kawaguchi2021a, title = {Electrochemically Induced Strain Evolution in Pt-Ni Alloy Nanoparticles Observed by Bragg Coherent Diffraction Imaging}, author = {Tomoya Kawaguchi and Vladimir Komanicky and Vitalii Latyshev and Wonsuk Cha and Evan Maxey and Ross Harder and Tetsu Ichitsubo and Hoydoo You}, url = {https://pubs.acs.org/doi/10.1021/acs.nanolett.1c00778}, doi = {https://doi.org/10.1021/acs.nanolett.1c00778}, year = {2021}, date = {2021-07-12}, journal = {Nano Letters}, volume = {21}, number = {14}, pages = {5945–5951}, abstract = {Strain is known to enhance the activity of the oxygen reduction reaction in catalytic platinum alloy nanoparticles, whose inactivity is the primary impediment to efficient fuel cells and metal–air batteries. Bragg coherent diffraction imaging (BCDI) was employed to reveal the strain evolution during the voltammetric cycling in Pt–Ni alloy nanoparticles composed of Pt_{2}Ni_{3}, Pt_{1}Ni_{1}, and Pt_{3}Ni_{2}. Analysis of the 3D strain images using a core–shell model shows that the strain as large as 5% is induced on Pt-rich shells due to Ni dissolution. The composition dependency of the strain on the shells is in excellent agreement with that of the catalytic activity. The present study demonstrates that BCDI enables quantitative determination of the strain on alloy nanoparticles during electrochemical reactions, which provides a means to exploit surface strain to design a wide range of electrocatalysts.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Strain is known to enhance the activity of the oxygen reduction reaction in catalytic platinum alloy nanoparticles, whose inactivity is the primary impediment to efficient fuel cells and metal–air batteries. Bragg coherent diffraction imaging (BCDI) was employed to reveal the strain evolution during the voltammetric cycling in Pt–Ni alloy nanoparticles composed of Pt2Ni3, Pt1Ni1, and Pt3Ni2. Analysis of the 3D strain images using a core–shell model shows that the strain as large as 5% is induced on Pt-rich shells due to Ni dissolution. The composition dependency of the strain on the shells is in excellent agreement with that of the catalytic activity. The present study demonstrates that BCDI enables quantitative determination of the strain on alloy nanoparticles during electrochemical reactions, which provides a means to exploit surface strain to design a wide range of electrocatalysts. |
 | Hiroshi Tanimura, Tomoki Hayashi, Martin Luckabauer, Tomoya Kawaguchi, Masato Wakeda, Hidemi Kato, Tetsu Ichitsubo (Review) Relaxation Behavior an Heterogeneous Structure of Metallic Glasses Journal Article Journal of the Society of Materials, Japan, 70 (5), pp. 374-380, 2021. @article{Tanimura2021, title = {(Review) Relaxation Behavior an Heterogeneous Structure of Metallic Glasses}, author = {Hiroshi Tanimura and Tomoki Hayashi and Martin Luckabauer and Tomoya Kawaguchi and Masato Wakeda and Hidemi Kato and Tetsu Ichitsubo}, url = {https://www.jstage.jst.go.jp/article/jsms/70/5/70_374/_pdf/-char/ja}, doi = {https://doi.org/10.2472/jsms.70.374}, year = {2021}, date = {2021-05-01}, journal = {Journal of the Society of Materials, Japan}, volume = {70}, number = {5}, pages = {374-380}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
 | Reshma R. Rao, Botao Huang, Yu Katayama, Jonathan Hwang, Tomoya Kawaguchi, Jaclyn R. Lunger, Jiayu Peng, Yirui Zhang, Asuka Morinaga, Hua Zhou, Hoydoo You, Yang Shao-Horn pH- and Cation-Dependent Water Oxidation on Rutile RuO2(110) Journal Article The Journal of Physical Chemistry C, 125 (15), pp. 8195-8207, 2021. @article{Rao2021a, title = {pH- and Cation-Dependent Water Oxidation on Rutile RuO_{2}(110)}, author = {Reshma R. Rao and Botao Huang and Yu Katayama and Jonathan Hwang and Tomoya Kawaguchi and Jaclyn R. Lunger and Jiayu Peng and Yirui Zhang and Asuka Morinaga and Hua Zhou and Hoydoo You and Yang Shao-Horn}, url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.1c00413}, doi = {https://doi.org/10.1021/acs.jpcc.1c00413}, year = {2021}, date = {2021-04-13}, journal = {The Journal of Physical Chemistry C}, volume = {125}, number = {15}, pages = {8195-8207}, abstract = {Noncovalent interactions at electrified interfaces are key to improving activity for the oxygen evolution reaction (OER). Here, we showed that on RuO_{2}(110) in alkaline solutions, OER activity is cation-dependent, being largest in 0.1 M KOH compared to LiOH and NaOH. Using crystal truncation rod analysis, −O is detected on the coordinatively unsaturated site at 1.5 V RHE in 0.1 M KOH, suggesting that the rate-determining step is −O + OH^{–} → -OOH + e^{–}, which is different from that in acid involving the final deprotonation of −OOH. The ordering of interfacial water in base was found to decrease with increasing potential and independent of cations. Using surface-enhanced infrared spectroscopy, the density of isolated water molecules (zero H-bonds) was found to increase, and the density of icelike water molecules (four H-bonds) decreases from Li^{+} to K^{+} at OER potentials. The higher activity of more isolated interfacial OH^{–} ions in the case of K^{+} and the lesser stabilization of −O intermediates by hydration water of K^{+} compared to Na^{+} and Li^{+} can result in higher OER activity for KOH. This work provides molecular details of the interface as a function of potential and electrolyte and enables the design of more active electrochemical interfaces.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Noncovalent interactions at electrified interfaces are key to improving activity for the oxygen evolution reaction (OER). Here, we showed that on RuO2(110) in alkaline solutions, OER activity is cation-dependent, being largest in 0.1 M KOH compared to LiOH and NaOH. Using crystal truncation rod analysis, −O is detected on the coordinatively unsaturated site at 1.5 V RHE in 0.1 M KOH, suggesting that the rate-determining step is −O + OH– → -OOH + e–, which is different from that in acid involving the final deprotonation of −OOH. The ordering of interfacial water in base was found to decrease with increasing potential and independent of cations. Using surface-enhanced infrared spectroscopy, the density of isolated water molecules (zero H-bonds) was found to increase, and the density of icelike water molecules (four H-bonds) decreases from Li+ to K+ at OER potentials. The higher activity of more isolated interfacial OH– ions in the case of K+ and the lesser stabilization of −O intermediates by hydration water of K+ compared to Na+ and Li+ can result in higher OER activity for KOH. This work provides molecular details of the interface as a function of potential and electrolyte and enables the design of more active electrochemical interfaces. |
 | Kohei Shimokawa, Taruto Atsumi, Norihiko L. Okamoto, Tomoya Kawaguchi, Susumu Imashuku, Kazuaki Wagatsuma, Masanobu Nakayama, Kiyoshi Kanamura, Tetsu Ichitsubo Structure Design of Long-Life Spinel-Oxide Cathode Materials for Magnesium Rechargeable Batteries Journal Article Advanced Materials, 33 (7), pp. 2007539, 2021. @article{shimokawa2021a, title = {Structure Design of Long-Life Spinel-Oxide Cathode Materials for Magnesium Rechargeable Batteries}, author = {Kohei Shimokawa and Taruto Atsumi and Norihiko L. Okamoto and Tomoya Kawaguchi and Susumu Imashuku and Kazuaki Wagatsuma and Masanobu Nakayama and Kiyoshi Kanamura and Tetsu Ichitsubo}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adma.202007539}, doi = {https://doi.org/10.1002/adma.202007539}, year = {2021}, date = {2021-01-18}, journal = {Advanced Materials}, volume = {33}, number = {7}, pages = {2007539}, abstract = {Development of metal-anode rechargeable batteries is a challenging issue. Especially, magnesium rechargeable batteries are promising in that Mg metal can be free from dendrite formation upon charging. However, in case of oxide cathode materials, inserted magnesium tends to form MgO-like rocksalt clusters in a parent phase even with another structure, which causes poor cyclability. Here, a design concept of high-performance cathode materials is shown, based on: i) selecting an element to destabilize the rocksalt-type structure and ii) utilizing the defect-spinel-type structure both to avoid the spinel-to-rocksalt reaction and to secure the migration path of Mg cations. This theoretical and experimental work substantiates that a defect-spinel-type ZnMnO_{3} meets the above criteria and shows excellent cycle performance exceeding 100 cycles upon Mg insertion/extraction with high potential (≈2.5 V vs Mg^{2+}/Mg) and capacity (≈100 mAh g^{−1}). Thus, this work would provide a design guideline of cathode materials for various multivalent rechargeable batteries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Development of metal-anode rechargeable batteries is a challenging issue. Especially, magnesium rechargeable batteries are promising in that Mg metal can be free from dendrite formation upon charging. However, in case of oxide cathode materials, inserted magnesium tends to form MgO-like rocksalt clusters in a parent phase even with another structure, which causes poor cyclability. Here, a design concept of high-performance cathode materials is shown, based on: i) selecting an element to destabilize the rocksalt-type structure and ii) utilizing the defect-spinel-type structure both to avoid the spinel-to-rocksalt reaction and to secure the migration path of Mg cations. This theoretical and experimental work substantiates that a defect-spinel-type ZnMnO3 meets the above criteria and shows excellent cycle performance exceeding 100 cycles upon Mg insertion/extraction with high potential (≈2.5 V vs Mg2+/Mg) and capacity (≈100 mAh g−1). Thus, this work would provide a design guideline of cathode materials for various multivalent rechargeable batteries. |
2020 |
|
 | Sungwook Choi, Myungwoo Chung, Dongjin Kim, Sungwon Kim, Kyuseok Yun, Wonsuk Cha, Ross Harder, Tomoya Kawaguchi, Yihua Liu, Andrew Ulvestad, Hoydoo You, Mee Kyung Song, and Hyunjung Kim In Situ Strain Evolution on Pt Nanoparticles during Hydrogen Peroxide Decomposition Journal Article Nano Letters, 20 (12), pp. 8541–8548, 2020. @article{Choi2020, title = {In Situ Strain Evolution on Pt Nanoparticles during Hydrogen Peroxide Decomposition}, author = {Sungwook Choi and Myungwoo Chung and Dongjin Kim and Sungwon Kim and Kyuseok Yun and Wonsuk Cha and Ross Harder and Tomoya Kawaguchi and Yihua Liu and Andrew Ulvestad and Hoydoo You and Mee Kyung Song and and Hyunjung Kim}, url = {https://pubs.acs.org/doi/10.1021/acs.nanolett.0c03005}, doi = {https://doi.org/10.1021/acs.nanolett.0c03005}, year = {2020}, date = {2020-11-11}, journal = {Nano Letters}, volume = {20}, number = {12}, pages = {8541–8548}, abstract = {Fundamental understanding of structural changes during catalytic reactions is crucial to understanding the underlying mechanisms and optimizing efficiencies. Surface energy and related catalytic mechanisms are widely studied. However, the catalyst lattice deformation induced by catalytic processes is not well understood. Here, we study the strain in an individual platinum (Pt) nanoparticle (NP) using Bragg coherent diffraction imaging under in situ oxidation and reduction reactions. When Pt NPs are exposed to H_{2}O_{2}, a typical oxidizer and an intermediate during the oxygen reduction reaction process, alternating overall strain distribution near the surface and inside the NP is observed at the (111) Bragg reflection. In contrast, relatively insignificant changes appear in the (200) reflection. Density functional theory calculations are employed to rationalize the anisotropic lattice strain in terms of induced stress by H_{2}O_{2} adsorption and decomposition on the Pt NP surface. Our study provides deeper insight into the activity–structure relationship in this system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fundamental understanding of structural changes during catalytic reactions is crucial to understanding the underlying mechanisms and optimizing efficiencies. Surface energy and related catalytic mechanisms are widely studied. However, the catalyst lattice deformation induced by catalytic processes is not well understood. Here, we study the strain in an individual platinum (Pt) nanoparticle (NP) using Bragg coherent diffraction imaging under in situ oxidation and reduction reactions. When Pt NPs are exposed to H2O2, a typical oxidizer and an intermediate during the oxygen reduction reaction process, alternating overall strain distribution near the surface and inside the NP is observed at the (111) Bragg reflection. In contrast, relatively insignificant changes appear in the (200) reflection. Density functional theory calculations are employed to rationalize the anisotropic lattice strain in terms of induced stress by H2O2 adsorption and decomposition on the Pt NP surface. Our study provides deeper insight into the activity–structure relationship in this system. |
 | Masatsugu Oishi, Keiji Shimoda, Koji Ohara, Daiki Kabutan, Tomoya Kawaguchi, Yoshiharu Uchimoto Disordered Cubic Spinel Structure in the Delithiated Li2MnO3 Revealed by Difference Pair Distribution Function Analysis Journal Article Journal of Physical Chemistry C, 124 , pp. 24081−24089, 2020. @article{Oishi2020, title = {Disordered Cubic Spinel Structure in the Delithiated Li2MnO3 Revealed by Difference Pair Distribution Function Analysis}, author = {Masatsugu Oishi and Keiji Shimoda and Koji Ohara and Daiki Kabutan and Tomoya Kawaguchi and Yoshiharu Uchimoto}, url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.0c07124}, doi = {https://doi.org/10.1021/acs.jpcc.0c07124}, year = {2020}, date = {2020-10-27}, journal = {Journal of Physical Chemistry C}, volume = {124}, pages = {24081−24089}, abstract = {An archetypical Li-rich layered oxide, Li_{2}MnO_{3}, shows a large initial charge capacity of ∼350 mAh g^{–1} with little oxidation of the constituent Mn ions; yet, the crystal structure of delithiated Li_{2}MnO_{3} is still unclarified because the structural disorder induced by the considerable Li extraction makes the analysis challenging. X-ray pair distribution function (PDF) analysis is a powerful tool to experimentally elucidate the structure of the disordered phase. Here, we conducted a comprehensive analysis with a focus on PDF analysis in combination with X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to reveal the disordered crystalline structure of the electrochemically delithiated Li_{2}MnO_{3}. The XRPD and TEM analyses clarified the formation of a low-crystallinity phase in the light of the average structure. The XAS and PDF analyses further revealed that the MnO_{6}-based framework was rearranged with maintenance of the MnO_{6} octahedral coordination after the initial charge. The difference pair distribution function (d-PDF) technique was therefore employed to extract the structural information of the low-crystallinity disordered phase. The delithiated phase was found to have a structure similar to that of the cubic spinel, LiMn_{2}O_{4}, rather than that of delithiated LiMn_{2}O_{4} (λ-MnO_{2}). In addition, the middle-range order of the delithiated phase deteriorated after the charge, indicating a decrease of coherent domain size to a single nm order. The composite structure formed after the first charge, therefore, consists of the disordered cubic spinel structure and unreacted Li_{2}MnO_{3}. The formation of the composite structure “activates” the electrode material structurally and eventually induces characteristic large capacity of this material.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An archetypical Li-rich layered oxide, Li2MnO3, shows a large initial charge capacity of ∼350 mAh g–1 with little oxidation of the constituent Mn ions; yet, the crystal structure of delithiated Li2MnO3 is still unclarified because the structural disorder induced by the considerable Li extraction makes the analysis challenging. X-ray pair distribution function (PDF) analysis is a powerful tool to experimentally elucidate the structure of the disordered phase. Here, we conducted a comprehensive analysis with a focus on PDF analysis in combination with X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to reveal the disordered crystalline structure of the electrochemically delithiated Li2MnO3. The XRPD and TEM analyses clarified the formation of a low-crystallinity phase in the light of the average structure. The XAS and PDF analyses further revealed that the MnO6-based framework was rearranged with maintenance of the MnO6 octahedral coordination after the initial charge. The difference pair distribution function (d-PDF) technique was therefore employed to extract the structural information of the low-crystallinity disordered phase. The delithiated phase was found to have a structure similar to that of the cubic spinel, LiMn2O4, rather than that of delithiated LiMn2O4 (λ-MnO2). In addition, the middle-range order of the delithiated phase deteriorated after the charge, indicating a decrease of coherent domain size to a single nm order. The composite structure formed after the first charge, therefore, consists of the disordered cubic spinel structure and unreacted Li2MnO3. The formation of the composite structure “activates” the electrode material structurally and eventually induces characteristic large capacity of this material. |
 | Tomoya Kawaguchi, Yihua Liua, Evguenia A.Karapetrova, Vladimir Komanicky, Hoydoo You In-situ to ex-situ in-plane structure evolution of stern layers on Pt(111) surface: Surface X-ray scattering studies Journal Article Journal of Electroanalytical Chemistry, 875 (15), pp. 114495, 2020. @article{Kawaguchi2020c, title = {In-situ to ex-situ in-plane structure evolution of stern layers on Pt(111) surface: Surface X-ray scattering studies}, author = {Tomoya Kawaguchi and Yihua Liua and Evguenia A.Karapetrova and Vladimir Komanicky and Hoydoo You}, url = {https://authors.elsevier.com/c/1cBNy5bbJ5c-uK https://www.sciencedirect.com/science/article/pii/S1572665720307220}, doi = {https://doi.org/10.1016/j.jelechem.2020.114495}, year = {2020}, date = {2020-07-24}, journal = {Journal of Electroanalytical Chemistry}, volume = {875}, number = {15}, pages = {114495}, abstract = {In-situ to ex-situ evolution of the Cs+ in-plane structure in electrochemical Stern layers are investigated on Pt(111) surface with surface X-ray scattering studies. The Cs+ single-sublattice (2 × 2) structure of the Stern layer formed in situ in 0.1 M CsF electrolyte [Liu et al., J. Phys. Chem. Lett., 9 (2018) 1265] evolves eventually to the two-sublattice (2 × 2) structure upon emersion from the electrolyte. While the Cs+ layers maintain the (2 × 2) symmetry, the ex situ layer increases the density progressively over several minutes by incorporating Cs+ ions of the electrolyte during the emersion process.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In-situ to ex-situ evolution of the Cs+ in-plane structure in electrochemical Stern layers are investigated on Pt(111) surface with surface X-ray scattering studies. The Cs+ single-sublattice (2 × 2) structure of the Stern layer formed in situ in 0.1 M CsF electrolyte [Liu et al., J. Phys. Chem. Lett., 9 (2018) 1265] evolves eventually to the two-sublattice (2 × 2) structure upon emersion from the electrolyte. While the Cs+ layers maintain the (2 × 2) symmetry, the ex situ layer increases the density progressively over several minutes by incorporating Cs+ ions of the electrolyte during the emersion process. |
 | Tomoya Kawaguchi, Reshma R. Rao, Jaclyn R. Lunger, Yihua Liu, Donald Walko, Evguenia A. Karapetrova, Vladimir Komanicky, Yang Shao-Horn, Hoydoo You Stern layers on RuO2 (100) and (110) in electrolyte: Surface X-ray scattering studies Journal Article Journal of Electroanalytical Chemistry, 875 (15), pp. 114228, 2020. @article{kawaguchi2020b, title = {Stern layers on RuO_{2} (100) and (110) in electrolyte: Surface X-ray scattering studies}, author = {Tomoya Kawaguchi and Reshma R. Rao and Jaclyn R. Lunger and Yihua Liu and Donald Walko and Evguenia A. Karapetrova and Vladimir Komanicky and Yang Shao-Horn and Hoydoo You }, url = {https://authors.elsevier.com/c/1cBNy5bbJ5c-Eo https://linkinghub.elsevier.com/retrieve/pii/S1572665720304562}, doi = {10.1016/j.jelechem.2020.114228}, year = {2020}, date = {2020-05-20}, journal = {Journal of Electroanalytical Chemistry}, volume = {875}, number = {15}, pages = {114228}, abstract = {Electrochemical Stern layers are observed on the surfaces of RuO_{2} single crystals in 0.1 M CsF electrolyte. The Stern layers formed at the interfaces of RuO_{2} (110) and (100) are compared to the previously reported Stern layer on Pt (111) [Liu et al., J. Phys. Chem. Lett., 9 (2018) 1265].While the Cs^{+} density profiles at the potentials close to hydrogen evolution reactions are similar, the hydration layers intervening the surface and the Cs^{+} layer are significantly denser on RuO_{2} surfaces than that on Pt(111) surface, reflecting the oxygen termination of RuO_{2} surfaces. The overall similarities between Stern layers on ruthenium surfaces and platinum surface suggest the universal presence of Stern layers in all well-defined solid-electrolyte interfaces. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemical Stern layers are observed on the surfaces of RuO2 single crystals in 0.1 M CsF electrolyte. The Stern layers formed at the interfaces of RuO2 (110) and (100) are compared to the previously reported Stern layer on Pt (111) [Liu et al., J. Phys. Chem. Lett., 9 (2018) 1265].While the Cs+ density profiles at the potentials close to hydrogen evolution reactions are similar, the hydration layers intervening the surface and the Cs+ layer are significantly denser on RuO2 surfaces than that on Pt(111) surface, reflecting the oxygen termination of RuO2 surfaces. The overall similarities between Stern layers on ruthenium surfaces and platinum surface suggest the universal presence of Stern layers in all well-defined solid-electrolyte interfaces. |
 | Koji Kimura, Hisao Kiuchi, Masahito Morita, Tomoya Kawaguchi, Kazuki Yoshii, Hikari Sakaebe, Kouichi Hayashi Development of a half-cell for X-ray structural analysis of liquid electrolytes in rechargeable batteries Journal Article Review of Scientific Instruments, 91 , pp. 033907, 2020. @article{Kimura2020, title = {Development of a half-cell for X-ray structural analysis of liquid electrolytes in rechargeable batteries}, author = {Koji Kimura and Hisao Kiuchi and Masahito Morita and Tomoya Kawaguchi and Kazuki Yoshii and Hikari Sakaebe and Kouichi Hayashi }, url = {https://aip.scitation.org/doi/10.1063/1.5124797}, doi = {https://doi.org/10.1063/1.5124797}, year = {2020}, date = {2020-03-24}, journal = {Review of Scientific Instruments}, volume = {91}, pages = {033907}, abstract = {A half-cell of the rechargeable Li-ion battery was developed to characterize an electrolyte structure using high energy X-ray total scattering measurements in combination with a two-dimensional X-ray detector. The scattering pattern consisted of strong Bragg peaks from electrodes and diffuse scatterings from sapphire windows, in addition to a weak halo pattern from the electrolyte. By selectively removing the signals of the electrodes and windows using specific numerical procedures, we could successfully extract the structural information of the electrolyte, which was in reasonable agreement with a reference data obtained from the electrolyte in a glass capillary. The present demonstration with a half-cell is expected to shed new light on operand characterization of the electrolyte structure during charging and discharging. }, keywords = {}, pubstate = {published}, tppubtype = {article} } A half-cell of the rechargeable Li-ion battery was developed to characterize an electrolyte structure using high energy X-ray total scattering measurements in combination with a two-dimensional X-ray detector. The scattering pattern consisted of strong Bragg peaks from electrodes and diffuse scatterings from sapphire windows, in addition to a weak halo pattern from the electrolyte. By selectively removing the signals of the electrodes and windows using specific numerical procedures, we could successfully extract the structural information of the electrolyte, which was in reasonable agreement with a reference data obtained from the electrolyte in a glass capillary. The present demonstration with a half-cell is expected to shed new light on operand characterization of the electrolyte structure during charging and discharging. |
 | Dong Young Chung, Pietro P. Lopes, Pedro Farinazzo Bergamo Dias Martins, Haiying He, Tomoya Kawaguchi, Peter Zapol, Hoydoo You, Dusan Tripkovic, Dusan Strmcnik, Yisi Zhu, Soenke Seifert, Sungsik Lee, Vojislav R. Stamenkovic, Nenad M. Markovic Dynamic stability of active sites in hydr(oxy)oxides for the oxygen evolution reaction Journal Article Nature Energy, 5 , pp. 222-230, 2020. @article{Dongyoung2020, title = {Dynamic stability of active sites in hydr(oxy)oxides for the oxygen evolution reaction}, author = {Dong Young Chung and Pietro P. Lopes and Pedro Farinazzo Bergamo Dias Martins and Haiying He and Tomoya Kawaguchi and Peter Zapol and Hoydoo You and Dusan Tripkovic and Dusan Strmcnik and Yisi Zhu and Soenke Seifert and Sungsik Lee and Vojislav R. Stamenkovic and Nenad M. Markovic}, url = {https://www.nature.com/articles/s41560-020-0576-y}, doi = {https://doi.org/10.1038/s41560-020-0576-y}, year = {2020}, date = {2020-03-16}, journal = {Nature Energy}, volume = {5}, pages = {222-230}, abstract = {The poor activity and stability of electrode materials for the oxygen evolution reaction are the main bottlenecks in the water-splitting reaction for H_{2} production. Here, by studying the activity–stability trends for the oxygen evolution reaction on conductive M^{1}O_{x}H_{y}, Fe–M^{1}O_{x}H_{y} and Fe–M^{1}M^{2}O_{x}H_{y} hydr(oxy)oxide clusters (M^{1} = Ni, Co, Fe; M^{2} = Mn, Co, Cu), we show that balancing the rates of Fe dissolution and redeposition over a MO_{x}H_{y} host establishes dynamically stable Fe active sites. Together with tuning the Fe content of the electrolyte, the strong interaction of Fe with the MO_{x}H_{y} host is the key to controlling the average number of Fe active sites present at the solid/liquid interface. We suggest that the Fe–M adsorption energy can therefore serve as a reaction descriptor that unifies oxygen evolution reaction catalysis on 3d transition-metal hydr(oxy)oxides in alkaline media. Thus, the introduction of dynamically stable active sites extends the design rules for creating active and stable interfaces.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The poor activity and stability of electrode materials for the oxygen evolution reaction are the main bottlenecks in the water-splitting reaction for H2 production. Here, by studying the activity–stability trends for the oxygen evolution reaction on conductive M1OxHy, Fe–M1OxHy and Fe–M1M2OxHy hydr(oxy)oxide clusters (M1 = Ni, Co, Fe; M2 = Mn, Co, Cu), we show that balancing the rates of Fe dissolution and redeposition over a MOxHy host establishes dynamically stable Fe active sites. Together with tuning the Fe content of the electrolyte, the strong interaction of Fe with the MOxHy host is the key to controlling the average number of Fe active sites present at the solid/liquid interface. We suggest that the Fe–M adsorption energy can therefore serve as a reaction descriptor that unifies oxygen evolution reaction catalysis on 3d transition-metal hydr(oxy)oxides in alkaline media. Thus, the introduction of dynamically stable active sites extends the design rules for creating active and stable interfaces. |
 | Tomoya Kawaguchi, Kazuya Tokuda, Seiya Okada, Makina Yabashi, Tetsu Ichitsubo, Noboru Yamada, Eiichiro Matsubara Direct observation of elastic softening immediately after femtosecond-laser excitation in a phase-change material Journal Article Physical Review B Rapid Communication, 101 , pp. 060302(R), 2020. @article{Kawaguchi2020a, title = {Direct observation of elastic softening immediately after femtosecond-laser excitation in a phase-change material}, author = {Tomoya Kawaguchi and Kazuya Tokuda and Seiya Okada and Makina Yabashi and Tetsu Ichitsubo and Noboru Yamada and Eiichiro Matsubara}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.101.060302}, doi = {https://doi.org/10.1103/PhysRevB.101.060302}, year = {2020}, date = {2020-02-24}, journal = {Physical Review B Rapid Communication}, volume = {101}, pages = {060302(R)}, abstract = {The generation and propagation of photoexcited elastic waves in crystalline Ge_{2}Sb_{2}Te_{5} were analyzed by picosecond time-resolved X-ray diffraction using a femtosecond (fs)-laser pump and an X-ray free-electron laser probe technique. The crystalline lattice anisotropically expanded initially in approximately 20 ps after the excitation. This was followed by a periodic oscillation of the lattice strain. The elastic stiffness along the cubic <111> direction had significantly softened during the initial expansion, and the strain magnitude was the largest in the <100> and <110> directions. This indicates that fs-laser excitation creates a shallower interlayer potential between the Te and Ge-Sb layers and eventually leads to softening of the elastic stiffness along the cubic <111> direction. Furthermore, this softened state increases the system’s sensitivity to an external stress field. This residual internal stress in a thin film enhances the selective formation of a particular type of variant during the symmetry change from cubic to rhombohedra. This causes the subsequent anisotropic expansion. These phenomena are quite interesting and align with the ultrafast amorphization of this material.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The generation and propagation of photoexcited elastic waves in crystalline Ge2Sb2Te5 were analyzed by picosecond time-resolved X-ray diffraction using a femtosecond (fs)-laser pump and an X-ray free-electron laser probe technique. The crystalline lattice anisotropically expanded initially in approximately 20 ps after the excitation. This was followed by a periodic oscillation of the lattice strain. The elastic stiffness along the cubic <111> direction had significantly softened during the initial expansion, and the strain magnitude was the largest in the <100> and <110> directions. This indicates that fs-laser excitation creates a shallower interlayer potential between the Te and Ge-Sb layers and eventually leads to softening of the elastic stiffness along the cubic <111> direction. Furthermore, this softened state increases the system’s sensitivity to an external stress field. This residual internal stress in a thin film enhances the selective formation of a particular type of variant during the symmetry change from cubic to rhombohedra. This causes the subsequent anisotropic expansion. These phenomena are quite interesting and align with the ultrafast amorphization of this material. |
2019 |
|
 | Tomoya Kawaguchi, Thomas F. Keller, Henning Runge, Luca Gelisio, Christoph Seitz, Young Y. Kim, Evan R. Maxey, Wonsuk Cha, Andrew Ulvestad, Stephan O. Hruszkewycz, Ross Harder, Ivan A. Vartanyants, Andreas Stierle, Hoydoo You Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in situ Bragg coherent diffraction imaging Journal Article Physical Review Letters, 123 , pp. 246001, 2019. @article{Kawaguchi2019a, title = {Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in situ Bragg coherent diffraction imaging}, author = {Tomoya Kawaguchi and Thomas F. Keller and Henning Runge and Luca Gelisio and Christoph Seitz and Young Y. Kim and Evan R. Maxey and Wonsuk Cha and Andrew Ulvestad and Stephan O. Hruszkewycz and Ross Harder and Ivan A. Vartanyants and Andreas Stierle and Hoydoo You }, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.246001}, doi = {10.1103/PhysRevLett.123.246001}, year = {2019}, date = {2019-12-13}, journal = {Physical Review Letters}, volume = {123}, pages = {246001}, abstract = {Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. 3D images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O_{2} and H_{2}. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. 3D images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O2 and H2. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles. |
 | Tomoya Kawaguchi, Wonsuk Cha, Vitalii Latyshev, Serhii Vorobiov, Vladimir Komanicky, Hoydoo You Study of the Internal Compositions of Binary Alloy Pd-Rh Nanoparticles by Using Bragg Coherent Diffraction Imaging Journal Article Journal of the Korean Physical Society, 75 (7), pp. 528-533, 2019. @article{Kawaguchi2019b, title = {Study of the Internal Compositions of Binary Alloy Pd-Rh Nanoparticles by Using Bragg Coherent Diffraction Imaging}, author = {Tomoya Kawaguchi and Wonsuk Cha and Vitalii Latyshev and Serhii Vorobiov and Vladimir Komanicky and Hoydoo You}, url = {https://link.springer.com/article/10.3938/jkps.75.528}, doi = {https://doi.org/10.3938/jkps.75.528}, year = {2019}, date = {2019-10-10}, journal = {Journal of the Korean Physical Society}, volume = {75}, number = {7}, pages = {528-533}, abstract = {Bragg coherent diffraction imaging (BCDI), a well-established technique for imaging the internal strain of nanoparticles, was used to image the internal compositional distribution of binary alloys in thermal equilibrium. The images experimentally obtained for Pd-Rh alloy nanoparticles are presented and discussed. A direct correspondence between the lattice strain and the compositional deviation is discussed with the derivation of the BCDI displacement field aided by illustrations. The correspondence suggests that the longitudinal derivative of the displacement field, the strain induced by compositional heterogeneity, can be quantitatively converted to 3D images of the compositional deviation from the particle average by using Vegard’s law. It also suggests that the transverse derivative can be qualitatively associated with the disorder of Bragg planes. The studied Pd-Rh alloy nanoparticle exhibited internal composition heterogeneity; the Rh composition tends to be high at edges and corners between facets and gradually decreases from the surface to the core of the particle.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Bragg coherent diffraction imaging (BCDI), a well-established technique for imaging the internal strain of nanoparticles, was used to image the internal compositional distribution of binary alloys in thermal equilibrium. The images experimentally obtained for Pd-Rh alloy nanoparticles are presented and discussed. A direct correspondence between the lattice strain and the compositional deviation is discussed with the derivation of the BCDI displacement field aided by illustrations. The correspondence suggests that the longitudinal derivative of the displacement field, the strain induced by compositional heterogeneity, can be quantitatively converted to 3D images of the compositional deviation from the particle average by using Vegard’s law. It also suggests that the transverse derivative can be qualitatively associated with the disorder of Bragg planes. The studied Pd-Rh alloy nanoparticle exhibited internal composition heterogeneity; the Rh composition tends to be high at edges and corners between facets and gradually decreases from the surface to the core of the particle. |
 | Miwa Murakami, Yoshiyuki Morita, Masao Yonemura, Keiji Shimoda, Masahiro Mori, Yukinori Koyama, Tomoya Kawaguchi, Katsutoshi Fukuda, Yoshihisa Ishikawa, Takashi Kamiyama, Yoshiharu Uchimoto, Zempachi Ogumi High Anionic Conductive Form of PbxSn2–xF4 Journal Article Chemistry of Materials, 31 (18), pp. 7704-7710, 2019. @article{Murakami2019, title = {High Anionic Conductive Form of Pb_{x}Sn_{2–x}F_{4}}, author = {Miwa Murakami and Yoshiyuki Morita and Masao Yonemura and Keiji Shimoda and Masahiro Mori and Yukinori Koyama and Tomoya Kawaguchi and Katsutoshi Fukuda and Yoshihisa Ishikawa and Takashi Kamiyama and Yoshiharu Uchimoto and Zempachi Ogumi}, url = {https://pubs.acs.org/doi/10.1021/acs.chemmater.9b02623}, doi = {https://doi.org/10.1021/acs.chemmater.9b02623}, year = {2019}, date = {2019-08-28}, journal = {Chemistry of Materials}, volume = {31}, number = {18}, pages = {7704-7710}, abstract = {A high anionic conductivity of ∼3.5 × 10^{–3} S cm^{–1} at room temperature is achieved for Pb_{x}Sn_{2–x}F_{4} (x = 1.21) obtained by annealing a mechanically milled PbF_{2}/SnF_{2} mixture at 400 °C. The observed synchrotron X-ray diffraction patterns indicate formation of a new tetragonal phase at x = 1.1–1.3. The Rietveld analysis of the neutron diffraction patterns leads to a unique structure consisting of two alternating layers, namely, a double Pb layer and a triple layer, each flanked by a single Sn layer. As the Rietveld analysis does not fully converge, the authors further apply high-resolution solid-state NMR (^{19}F, ^{119}Sn, and ^{207}Pb) to confirm the structure. Further, the ^{19}F-^{207}Pb cross-polarization experiment shows that most F^{–} ions, except for those that lie between the double Pb layers, contribute to its high ionic conductivity. The high conductivity is also attributed to structural flexibility of the triple Pb layers, indicated by temperature-dependent ^{207}Pb NMR spectra.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A high anionic conductivity of ∼3.5 × 10–3 S cm–1 at room temperature is achieved for PbxSn2–xF4 (x = 1.21) obtained by annealing a mechanically milled PbF2/SnF2 mixture at 400 °C. The observed synchrotron X-ray diffraction patterns indicate formation of a new tetragonal phase at x = 1.1–1.3. The Rietveld analysis of the neutron diffraction patterns leads to a unique structure consisting of two alternating layers, namely, a double Pb layer and a triple layer, each flanked by a single Sn layer. As the Rietveld analysis does not fully converge, the authors further apply high-resolution solid-state NMR (19F, 119Sn, and 207Pb) to confirm the structure. Further, the 19F-207Pb cross-polarization experiment shows that most F– ions, except for those that lie between the double Pb layers, contribute to its high ionic conductivity. The high conductivity is also attributed to structural flexibility of the triple Pb layers, indicated by temperature-dependent 207Pb NMR spectra. |
 | Zhihai H. Zhu, Joerg Strempfer, Reshma R. Rao, Connor A. Occhialini, Jonathan Pelliciari, Yongseong Choi, Tomoya Kawaguchi, Hoydoo You, John F. Mitchell, Yang Shao-Horn, and Riccardo Comin Anomalous Antiferromagnetism in Metallic RuO2 Determined by Resonant X-ray Scattering Journal Article Phycal Review Letters, 122 , pp. 017202, 2019. @article{Zhu2018, title = {Anomalous Antiferromagnetism in Metallic RuO_{2} Determined by Resonant X-ray Scattering}, author = {Zhihai H. Zhu and Joerg Strempfer and Reshma R. Rao and Connor A. Occhialini and Jonathan Pelliciari and Yongseong Choi and Tomoya Kawaguchi and Hoydoo You and John F. Mitchell and Yang Shao-Horn and and Riccardo Comin}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.017202}, doi = {https://doi.org/10.1103/PhysRevLett.122.017202}, year = {2019}, date = {2019-01-03}, journal = {Phycal Review Letters}, volume = {122}, pages = {017202}, abstract = {We studied the magnetic ordering of both thin films and bulk crystals of rutile RuO_{2} using resonant X-ray scattering near the Ru L_{2} absorption edge. Combining a polarization analysis and azimuthal-angle dependence of the resonant reflection characteristic of the antiferromagentic ordering, we have established the G-type antiferromagnetism in RuO_{2} with T_{N} > 300 K. In addition to igniting an inquiry into the itinerant antiferromagnetism, the revelation of the endurance even in a nanometer-thick film lays the foundations for potential applications of RuO_{2} in antiferromagnetic spintronics}, keywords = {}, pubstate = {published}, tppubtype = {article} } We studied the magnetic ordering of both thin films and bulk crystals of rutile RuO2 using resonant X-ray scattering near the Ru L2 absorption edge. Combining a polarization analysis and azimuthal-angle dependence of the resonant reflection characteristic of the antiferromagentic ordering, we have established the G-type antiferromagnetism in RuO2 with TN > 300 K. In addition to igniting an inquiry into the itinerant antiferromagnetism, the revelation of the endurance even in a nanometer-thick film lays the foundations for potential applications of RuO2 in antiferromagnetic spintronics |
 | Takuya Hatakeyama, Norihiko L Okamoto, Kohei Shimokawa, Hongyi Li, Aiko Nakao, Yoshiharu Uchimoto, Hiroshi Tanimura, Tomoya Kawaguchi, Tetsu Ichitsubo Electrochemical phase transformation accompanied with Mg extraction and insertion in a spinel MgMn2O4 cathode material Journal Article Phys. Chem. Chem. Phys., 21 , pp. 23749-23757, 2019. @article{C9CP04461B, title = {Electrochemical phase transformation accompanied with Mg extraction and insertion in a spinel MgMn_{2}O_{4} cathode material}, author = {Takuya Hatakeyama and Norihiko L Okamoto and Kohei Shimokawa and Hongyi Li and Aiko Nakao and Yoshiharu Uchimoto and Hiroshi Tanimura and Tomoya Kawaguchi and Tetsu Ichitsubo}, url = {http://dx.doi.org/10.1039/C9CP04461B}, doi = {10.1039/C9CP04461B}, year = {2019}, date = {2019-01-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {21}, pages = {23749-23757}, publisher = {The Royal Society of Chemistry}, abstract = {One of the key challenges when developing magnesium rechargeable batteries (MRB) is to develop Mg-intercalation cathodes exhibiting higher redox potentials with larger specific capacities. Although Mg-transition-metal spinel oxides have been shown to be excellent candidates as MRB cathode materials by utilizing the valence change from trivalent to divalent of transition metals starting from Mg insertion, there is no clear evidence to date that Mg can be indeed extracted from the initial spinel hosts by utilizing the change from trivalent to quadrivalent. In this work, we clearly present various experimental evidences of the electrochemical extraction of Mg from spinel MgMn_{2}O_{4}. The present electrochemical charge, i.e., extraction treatment of Mg, was performed in an ionic liquid at 150 °C to ensure Mg hopping in the spinel host. Our analyses show that Mg can be extracted from Mg_{1−x}Mn_{2}O_{4} up to x = 0.4 and, afterwards, successively be inserted into the Mg-extracted (demagnesiated) host via a two-phase reaction between tetragonal and cubic spinels. Finally, we also discuss the difference in electrochemical features between LiMn_{2}O_{4} and MgMn_{2}O_{4}.}, keywords = {}, pubstate = {published}, tppubtype = {article} } One of the key challenges when developing magnesium rechargeable batteries (MRB) is to develop Mg-intercalation cathodes exhibiting higher redox potentials with larger specific capacities. Although Mg-transition-metal spinel oxides have been shown to be excellent candidates as MRB cathode materials by utilizing the valence change from trivalent to divalent of transition metals starting from Mg insertion, there is no clear evidence to date that Mg can be indeed extracted from the initial spinel hosts by utilizing the change from trivalent to quadrivalent. In this work, we clearly present various experimental evidences of the electrochemical extraction of Mg from spinel MgMn2O4. The present electrochemical charge, i.e., extraction treatment of Mg, was performed in an ionic liquid at 150 °C to ensure Mg hopping in the spinel host. Our analyses show that Mg can be extracted from Mg1−xMn2O4 up to x = 0.4 and, afterwards, successively be inserted into the Mg-extracted (demagnesiated) host via a two-phase reaction between tetragonal and cubic spinels. Finally, we also discuss the difference in electrochemical features between LiMn2O4 and MgMn2O4. |
2018 |
|
 | Vincent Esposito, Laurenz Rettig, Elisabeth M. Bothschafter, Yunpei Deng, Christian Dornes, Lucas Huber, Tim Huber, Gerhard Ingold, Yuichi Inubushi, Tetsuo Katayama, Tomoya Kawaguchi, Henrik Lemke, Kanade Ogawa, Shigeki Owada, Milan Radovic, Mahesh Ramakrishnan, Zoran Ristic, ValerioScagnoli, Yoshikazu Tanaka, Tadashi Togashi, Kensuke Tono, Ivan Usov, Yoav W. Windsor, Makina Yabashi, Steven L. Johnson, Paul Beaud, Urs Staub Dynamics of the Photoinduced Insulator-to-Metal Transition in a Nickelate Film Journal Article Structural Dynamics, 5 , pp. 064501, 2018. @article{Esposito2018, title = {Dynamics of the Photoinduced Insulator-to-Metal Transition in a Nickelate Film}, author = {Vincent Esposito and Laurenz Rettig and Elisabeth M. Bothschafter and Yunpei Deng and Christian Dornes and Lucas Huber and Tim Huber and Gerhard Ingold and Yuichi Inubushi and Tetsuo Katayama and Tomoya Kawaguchi and Henrik Lemke and Kanade Ogawa and Shigeki Owada and Milan Radovic and Mahesh Ramakrishnan and Zoran Ristic and ValerioScagnoli and Yoshikazu Tanaka and Tadashi Togashi and Kensuke Tono and Ivan Usov and Yoav W. Windsor and Makina Yabashi and Steven L. Johnson and Paul Beaud and Urs Staub}, url = {https://aca.scitation.org/doi/10.1063/1.5063530}, doi = {https://doi.org/10.1063/1.5063530}, year = {2018}, date = {2018-12-28}, journal = {Structural Dynamics}, volume = {5}, pages = {064501}, abstract = {The control of materials properties with light is a promising approach towards the realization of faster and smaller electronic devices. With phases that can be controlled via strain, pressure, chemical composition or dimensionality, nickelates are good candidates for the development of a new generation of high performance and low consumption devices. Here we analyze the photoinduced dynamics in a single crystalline NdNiO_{3} film upon excitation across the electronic gap. Using time-resolved reflectivity and resonant x-ray diffraction, we show that the pump pulse induces an insulator-to-metal transition, accompanied by the melting of the charge order. Finally we compare our results to similar studies in manganites and show that the same model can be used to describe the dynamics in nickelates, hinting towards a unified description of these photoinduced phase transitions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The control of materials properties with light is a promising approach towards the realization of faster and smaller electronic devices. With phases that can be controlled via strain, pressure, chemical composition or dimensionality, nickelates are good candidates for the development of a new generation of high performance and low consumption devices. Here we analyze the photoinduced dynamics in a single crystalline NdNiO3 film upon excitation across the electronic gap. Using time-resolved reflectivity and resonant x-ray diffraction, we show that the pump pulse induces an insulator-to-metal transition, accompanied by the melting of the charge order. Finally we compare our results to similar studies in manganites and show that the same model can be used to describe the dynamics in nickelates, hinting towards a unified description of these photoinduced phase transitions. |
 | Atsushi Sakuda, Koji Ohara, Tomoya Kawaguchi, Katsutoshi Fukuda, Koji Nakanishi, Hajime Arai, Yoshiharu Uchimoto, Toshiaki Ohta, Eiichiro Matsubara, Zempachi Ogumi, Kentaro Kuratani, Hironori Kobayashi, Masahiro Shikano, Tomonari Takeuchi, Hikari Sakaebe A Reversible Rocksalt to Amorphous Phase Transition Involving Anion Redox Journal Article Scientific Reports, 8 (1), pp. 15086, 2018, ISBN: 4159801833518. @article{sakuda2018, title = {A Reversible Rocksalt to Amorphous Phase Transition Involving Anion Redox}, author = {Atsushi Sakuda and Koji Ohara and Tomoya Kawaguchi and Katsutoshi Fukuda and Koji Nakanishi and Hajime Arai and Yoshiharu Uchimoto and Toshiaki Ohta and Eiichiro Matsubara and Zempachi Ogumi and Kentaro Kuratani and Hironori Kobayashi and Masahiro Shikano and Tomonari Takeuchi and Hikari Sakaebe}, url = {http://www.nature.com/articles/s41598-018-33518-4}, doi = {10.1038/s41598-018-33518-4}, isbn = {4159801833518}, year = {2018}, date = {2018-10-10}, journal = {Scientific Reports}, volume = {8}, number = {1}, pages = {15086}, abstract = {The charge-discharge capacity of lithium secondary batteries is dependent on how many lithium ions can be reversibly extracted from (charge) and inserted into (discharge) the electrode active materials. In contrast, large structural changes during charging/discharging are unavoidable for electrode materials with large capacities, and thus there is great demand for developing materials with reversible structures. Herein, we demonstrate a reversible rocksalt to amorphous phase transition involving anion redox in a Li_{2}TiS_{3} electrode active material with NaCl-type structure. We revealed that the lithium extraction during charging involves a change in site of the sulfur atom and the formation of S−S disulfide bonds, leading to a decrease in the crystallinity. Our results show great promise for the development of long-life lithium insertion/extraction materials, because the structural change clarified here is somewhat similar to that of optical phase-change materials used in DVD-RW discs, which exhibit excellent reversibility of the transition between crystalline and amorphous phase.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The charge-discharge capacity of lithium secondary batteries is dependent on how many lithium ions can be reversibly extracted from (charge) and inserted into (discharge) the electrode active materials. In contrast, large structural changes during charging/discharging are unavoidable for electrode materials with large capacities, and thus there is great demand for developing materials with reversible structures. Herein, we demonstrate a reversible rocksalt to amorphous phase transition involving anion redox in a Li2TiS3 electrode active material with NaCl-type structure. We revealed that the lithium extraction during charging involves a change in site of the sulfur atom and the formation of S−S disulfide bonds, leading to a decrease in the crystallinity. Our results show great promise for the development of long-life lithium insertion/extraction materials, because the structural change clarified here is somewhat similar to that of optical phase-change materials used in DVD-RW discs, which exhibit excellent reversibility of the transition between crystalline and amorphous phase. |
 | Hideyuki Komatsu, Taketoshi Minato, Toshiyuki Matsunaga, Keiji Shimoda, Tomoya Kawaguchi, Katsutoshi Fukuda, Koji Nakanishi, Hajime Tanida, Shunsuke Kobayashi, Tsukasa Hirayama, Yuichi Ikuhara, Hajime Arai, Yoshio Ukyo, Yoshiharu Uchimoto, Eiichiro Matsubara, Zempachi Ogumi Site-Selective Analysis of Nickel-Substituted Li-Rich Layered Material: Migration and Role of Transition Metal at Charging and Discharging Journal Article J. Phys. Chem. C, 122 (35), pp. 20099-20107, 2018, ISSN: 1932-7447. @article{Komatsu2018, title = {Site-Selective Analysis of Nickel-Substituted Li-Rich Layered Material: Migration and Role of Transition Metal at Charging and Discharging}, author = {Hideyuki Komatsu and Taketoshi Minato and Toshiyuki Matsunaga and Keiji Shimoda and Tomoya Kawaguchi and Katsutoshi Fukuda and Koji Nakanishi and Hajime Tanida and Shunsuke Kobayashi and Tsukasa Hirayama and Yuichi Ikuhara and Hajime Arai and Yoshio Ukyo and Yoshiharu Uchimoto and Eiichiro Matsubara and Zempachi Ogumi}, url = {http://pubs.acs.org/doi/10.1021/acs.jpcc.8b05539}, doi = {10.1021/acs.jpcc.8b05539}, issn = {1932-7447}, year = {2018}, date = {2018-08-17}, journal = {J. Phys. Chem. C}, volume = {122}, number = {35}, pages = {20099-20107}, abstract = {Li-rich type manganese oxides are one of the most promising cathodes for lithium-ion batteries in recent years; thanks to their high energy density. In these cathodes, partial substitution of manganese by other transition metals such as nickel and cobalt has been proposed and shown to be effective in improving the performance; however, the role of such metals in the battery performance has not been clarified. We examined Ni-substituted Li_{2}MnO_{3} as a model of Li_{2}MeO_{3} solid-solution cathodes to understand the effect of the substituted Ni on the electrode performances by using a combination of resonant X-ray diffraction spectroscopy (RXDS) and operando X-ray absorption spectroscopy. The capacity and cyclability were improved by substituting Ni into the Li_{2}MnO_{3} phase, which suggests its important roles in the cathodes. The change in the oxidation state and transbilayer migration of the transition metals as a function of the operating potential during the first charge–discharge processes were revealed by the site-selective analysis of RXDS. We discuss the influence of the irreversible and reversible migration of Ni and Mn ions on the electrode performance.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Li-rich type manganese oxides are one of the most promising cathodes for lithium-ion batteries in recent years; thanks to their high energy density. In these cathodes, partial substitution of manganese by other transition metals such as nickel and cobalt has been proposed and shown to be effective in improving the performance; however, the role of such metals in the battery performance has not been clarified. We examined Ni-substituted Li2MnO3 as a model of Li2MeO3 solid-solution cathodes to understand the effect of the substituted Ni on the electrode performances by using a combination of resonant X-ray diffraction spectroscopy (RXDS) and operando X-ray absorption spectroscopy. The capacity and cyclability were improved by substituting Ni into the Li2MnO3 phase, which suggests its important roles in the cathodes. The change in the oxidation state and transbilayer migration of the transition metals as a function of the operating potential during the first charge–discharge processes were revealed by the site-selective analysis of RXDS. We discuss the influence of the irreversible and reversible migration of Ni and Mn ions on the electrode performance. |
 | Tomoya Kawaguchi, Masashi Sakaida, Masatsugu Oishi, Tetsu Ichitsubo, Katsutoshi Fukuda, Satoshi Toyoda, Eiichiro Matsubara Strain-Induced Stabilization of Charged State in Li-Rich Layered Transition Metal Oxide for Lithium Ion Batteries Journal Article J. Phys. Chem. C, 122 (34), pp. 19298–19308, 2018, ISSN: 1932-7447. @article{Kawaguchi2018a, title = {Strain-Induced Stabilization of Charged State in Li-Rich Layered Transition Metal Oxide for Lithium Ion Batteries}, author = {Tomoya Kawaguchi and Masashi Sakaida and Masatsugu Oishi and Tetsu Ichitsubo and Katsutoshi Fukuda and Satoshi Toyoda and Eiichiro Matsubara}, url = {https://pubs.acs.org/articlesonrequest/AOR-C8SjZ5pB5xbnrbGbxeVM http://pubs.acs.org/doi/10.1021/acs.jpcc.8b03205}, doi = {10.1021/acs.jpcc.8b03205}, issn = {1932-7447}, year = {2018}, date = {2018-08-08}, journal = {J. Phys. Chem. C}, volume = {122}, number = {34}, pages = {19298–19308}, abstract = {Li-rich layered oxide (LLO) is a promising cathode material for lithium-ion batteries because of its large capacity in comparison with conventional layered rock-salt structure materials. In contrast to the conventional materials, it is known that LLO of 3d transition metal has nanodomain microstructure; however, roles of each domain and effects of strain, induced by the microstructure, on electrode properties are still unclear. In this study, the influence of the strain on an electronic structure is studied to elucidate the stabilization mechanism of LLO material Li[Li_{0.2}Ni_{0.2}Mn_{0.6}]O_{2} in the charged state by using resonant X-ray diffraction spectroscopy (RXDS), X-ray diffraction and X-ray absorption spectroscopy (XAS) in combination with \textit{ab initio} calculation. RXDS of a superlattice peak and XAS at Mn and Ni K-edges unveil that this material has a microstructure consisting of Mn-rich and Ni-rich domains, whose structures are similar to Li_{2}MnO_{3} and LiNiO_{2}, respectively. In the Ni-rich domain, trigonal distortion in the NiO_{6} octahedral cluster is induced by an elastic constraint due to the microstructure. Hybridization between oxygen p- and nickel d-orbitals are enhanced by the distortion as revealed both by XAS and \textit{ab initio} calculation, accounting for stabilization of the charged state by alleviating the direct hole formation on oxygen p-orbital that usually destabilizes the charged material.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Li-rich layered oxide (LLO) is a promising cathode material for lithium-ion batteries because of its large capacity in comparison with conventional layered rock-salt structure materials. In contrast to the conventional materials, it is known that LLO of 3d transition metal has nanodomain microstructure; however, roles of each domain and effects of strain, induced by the microstructure, on electrode properties are still unclear. In this study, the influence of the strain on an electronic structure is studied to elucidate the stabilization mechanism of LLO material Li[Li0.2Ni0.2Mn0.6]O2 in the charged state by using resonant X-ray diffraction spectroscopy (RXDS), X-ray diffraction and X-ray absorption spectroscopy (XAS) in combination with ab initio calculation. RXDS of a superlattice peak and XAS at Mn and Ni K-edges unveil that this material has a microstructure consisting of Mn-rich and Ni-rich domains, whose structures are similar to Li2MnO3 and LiNiO2, respectively. In the Ni-rich domain, trigonal distortion in the NiO6 octahedral cluster is induced by an elastic constraint due to the microstructure. Hybridization between oxygen p- and nickel d-orbitals are enhanced by the distortion as revealed both by XAS and ab initio calculation, accounting for stabilization of the charged state by alleviating the direct hole formation on oxygen p-orbital that usually destabilizes the charged material. |
 | Kazuto Koganei, Atsushi Sakuda, Tomonari Takeuchi, Hikari Sakaebe, Hironori Kobayashi, Hiroyuki Kageyama, Tomoya Kawaguchi, Hisao Kiuchi, Koji Nakanishi, Masashi Yoshimura, Toshiaki Ohta, Toshiharu Fukunaga, Eiichiro Matsubara Analysis of the Discharge/Charge Mechanism in VS4 Positive Electrode Material Journal Article Solid State Ionics, 323 , pp. 32–36, 2018, ISSN: 01672738. @article{Koganei2018b, title = {Analysis of the Discharge/Charge Mechanism in VS_{4} Positive Electrode Material}, author = {Kazuto Koganei and Atsushi Sakuda and Tomonari Takeuchi and Hikari Sakaebe and Hironori Kobayashi and Hiroyuki Kageyama and Tomoya Kawaguchi and Hisao Kiuchi and Koji Nakanishi and Masashi Yoshimura and Toshiaki Ohta and Toshiharu Fukunaga and Eiichiro Matsubara}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0167273817307567}, doi = {10.1016/j.ssi.2018.05.010}, issn = {01672738}, year = {2018}, date = {2018-05-17}, journal = {Solid State Ionics}, volume = {323}, pages = {32--36}, abstract = {Among transition metal sulfides, VS_{4} is a promising candidate material for the positive electrode in rechargeable Li/metal-sulfide batteries, due to its long, flat plateau at about 2.0 V and its high theoretical capacity (1195 mAh g^{−1}). In this study, we prepared VS_{4} positive electrode material by heating in a sealed tube, and studied local structural changes during charge/discharge cycles via X-ray absorption and scattering spectroscopies, focusing on the reversibility of VS_{4}. The findings reveal that a VS_{4}-like local structure was formed in the first cycle, and that subsequent cycles showed reversible changes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Among transition metal sulfides, VS4 is a promising candidate material for the positive electrode in rechargeable Li/metal-sulfide batteries, due to its long, flat plateau at about 2.0 V and its high theoretical capacity (1195 mAh g−1). In this study, we prepared VS4 positive electrode material by heating in a sealed tube, and studied local structural changes during charge/discharge cycles via X-ray absorption and scattering spectroscopies, focusing on the reversibility of VS4. The findings reveal that a VS4-like local structure was formed in the first cycle, and that subsequent cycles showed reversible changes. |
 | Tomoya Kawaguchi, Yihua Liu, Anthony Reiter, Christian Cammarota, Michael S. Pierce, Hoydoo You Direct Determination of One-Dimensional Interphase Structures Using Normalized Crystal Truncation Rod Analysis Journal Article J. Appl. Crystallogr., 51 , pp. 1–6, 2018. @article{Kawaguchi2018, title = {Direct Determination of One-Dimensional Interphase Structures Using Normalized Crystal Truncation Rod Analysis }, author = {Tomoya Kawaguchi and Yihua Liu and Anthony Reiter and Christian Cammarota and Michael S. Pierce and Hoydoo You}, doi = {10.1107/S1600576718004326}, year = {2018}, date = {2018-01-01}, journal = {J. Appl. Crystallogr.}, volume = {51}, pages = {1--6}, publisher = {International Union of Crystallography}, abstract = {A one-dimensional non-iterative direct method was employed for normalized crystal truncation rod analysis. The non-iterative approach, utilizing the Kramers-Kronig relation, avoids the ambiguities due to an improper initial model or incomplete convergence in the conventional iterative methods. The validity and limitations of the present method are demonstrated through both numerical simulations and experiments with Pt(111) in a 0.1 M CsF aqueous solution. The present method is compared with conventional iterative phase-retrieval methods.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A one-dimensional non-iterative direct method was employed for normalized crystal truncation rod analysis. The non-iterative approach, utilizing the Kramers-Kronig relation, avoids the ambiguities due to an improper initial model or incomplete convergence in the conventional iterative methods. The validity and limitations of the present method are demonstrated through both numerical simulations and experiments with Pt(111) in a 0.1 M CsF aqueous solution. The present method is compared with conventional iterative phase-retrieval methods. |
 | Tomonari Takeuchi, Hiroyuki Kageyama, Noboru Taguchi, Koji Nakanishi, Tomoya Kawaguchi, Koji Ohara, Katsutoshi Fukuda, Atsushi Sakuda, Toshiaki Ohta, Toshiharu Fukunaga, Hikari Sakaebe, Hironori Kobayashi, Eiichiro Matsubara Structure Analyses of Fe-Substituted Li2S-Based Positive Electrode Materials for Li-S Batteries Journal Article Solid State Ionics, 320 (September 2017), pp. 387–391, 2018, ISSN: 01672738. @article{Takeuchi2018, title = {Structure Analyses of Fe-Substituted Li_{2}S-Based Positive Electrode Materials for Li-S Batteries}, author = {Tomonari Takeuchi and Hiroyuki Kageyama and Noboru Taguchi and Koji Nakanishi and Tomoya Kawaguchi and Koji Ohara and Katsutoshi Fukuda and Atsushi Sakuda and Toshiaki Ohta and Toshiharu Fukunaga and Hikari Sakaebe and Hironori Kobayashi and Eiichiro Matsubara}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0167273817309037}, doi = {10.1016/j.ssi.2018.03.028}, issn = {01672738}, year = {2018}, date = {2018-01-01}, journal = {Solid State Ionics}, volume = {320}, number = {September 2017}, pages = {387--391}, publisher = {Elsevier}, abstract = {The structure of Fe-substituted Li_{2}S-based positive electrode material Li_{8}FeS_{5} was analyzed using high-energy X- ray total scattering measurements. Pair distribution function (PDF) analyses indicated that the mechanically milled Li_{8}FeS_{5} sample could best be described as having an anti-fluorite structure in which Fe ions partially occupy Li sites in the Fm3m unit cell. The electrochemical properties of a cell utilizing Li_{8}FeS_{5} as the positive electrode were also consistent with this structural model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The structure of Fe-substituted Li2S-based positive electrode material Li8FeS5 was analyzed using high-energy X- ray total scattering measurements. Pair distribution function (PDF) analyses indicated that the mechanically milled Li8FeS5 sample could best be described as having an anti-fluorite structure in which Fe ions partially occupy Li sites in the Fm3m unit cell. The electrochemical properties of a cell utilizing Li8FeS5 as the positive electrode were also consistent with this structural model. |
 | Yihua Liu, Tomoya Kawaguchi, Michael S Pierce, Vladimir Komanicky, Hoydoo You Layering and Ordering in Electrochemical Double Layers Journal Article J. Phys. Chem. Lett., 9 , pp. 1265–1271, 2018, ISSN: 1948-7185. @article{Liu2018, title = {Layering and Ordering in Electrochemical Double Layers}, author = {Yihua Liu and Tomoya Kawaguchi and Michael S Pierce and Vladimir Komanicky and Hoydoo You}, url = {http://pubs.acs.org/doi/10.1021/acs.jpclett.8b00123}, doi = {10.1021/acs.jpclett.8b00123}, issn = {1948-7185}, year = {2018}, date = {2018-01-01}, journal = {J. Phys. Chem. Lett.}, volume = {9}, pages = {1265--1271}, abstract = {Electrochemical double layers (EDL) form at electrified interfaces. Whereas the Gouy–Chapman model describes moderately charged EDL, the formation of Stern layers was predicted for highly charged EDL. Our results provide structural evidence for a Stern layer of cations at potentials close to hydrogen evolution in alkali fluoride and chloride electrolytes. Layering was observed by X-ray crystal truncation rods and atomic-scale recoil responses of Pt(111) surface layers. Ordering in the layer was confirmed by glancing-incidence in-plane diffraction measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemical double layers (EDL) form at electrified interfaces. Whereas the Gouy–Chapman model describes moderately charged EDL, the formation of Stern layers was predicted for highly charged EDL. Our results provide structural evidence for a Stern layer of cations at potentials close to hydrogen evolution in alkali fluoride and chloride electrolytes. Layering was observed by X-ray crystal truncation rods and atomic-scale recoil responses of Pt(111) surface layers. Ordering in the layer was confirmed by glancing-incidence in-plane diffraction measurements. |
2017 |
Atsushi Sakuda, Kentaro Kuratani, Tomonari Takeuchi, Hisao Kiuchi, Tomoya Kawaguchi, Masahiro Shikano, Hikari Sakaebe, Hironori Kobayashi Cubic Rocksalt Li2SnS3 and a Solid Solution with Li3NbS4 Prepared by Mechanochemical Synthesis Journal Article Electrochemistry, 85 (9), pp. 580–584, 2017, ISSN: 1344-3542. @article{Sakuda2017, title = {Cubic Rocksalt Li_{2}SnS_{3} and a Solid Solution with Li_{3}NbS_{4} Prepared by Mechanochemical Synthesis}, author = {Atsushi Sakuda and Kentaro Kuratani and Tomonari Takeuchi and Hisao Kiuchi and Tomoya Kawaguchi and Masahiro Shikano and Hikari Sakaebe and Hironori Kobayashi}, url = {https://www.jstage.jst.go.jp/article/electrochemistry/85/9/85_17-E00038/_article}, doi = {10.5796/electrochemistry.85.580}, issn = {1344-3542}, year = {2017}, date = {2017-09-01}, journal = {Electrochemistry}, volume = {85}, number = {9}, pages = {580--584}, publisher = {The Electrochemical Society of Japan}, abstract = {Cubic Li_{2}SnS_{3} with NaCl structure and the solid solution with Li_{3}NbS_{4} were developed by mechanochemical synthesis. Cubic Li_{2}SnS_{3} is a metastable phase, and the previously reported monoclinic Li_{2}SnS_{3} is a stable phase. Cubic Li_{2}SnS_{3} acts as an ionic conductor, and the solid solution of Li_{3}NbS_{4}-Li_{2}SnS_{3} can be used as an electrode active material in lithium secondary batteries. Li_{2.933}Nb_{0.8}Sn_{0.267}S_{4} and Li_{2.857}Nb_{0.571}Sn_{0.571}S_{4} shows large reversible capacities of 318 and 286 mAh g^{−1}, respectively. The capacity of these materials depends less on the niobium content than on the electrical conductivity. The reversible capacity in the 2-V region is mainly attributable to redox reactions involving rather sulfur than tin.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Cubic Li2SnS3 with NaCl structure and the solid solution with Li3NbS4 were developed by mechanochemical synthesis. Cubic Li2SnS3 is a metastable phase, and the previously reported monoclinic Li2SnS3 is a stable phase. Cubic Li2SnS3 acts as an ionic conductor, and the solid solution of Li3NbS4-Li2SnS3 can be used as an electrode active material in lithium secondary batteries. Li2.933Nb0.8Sn0.267S4 and Li2.857Nb0.571Sn0.571S4 shows large reversible capacities of 318 and 286 mAh g−1, respectively. The capacity of these materials depends less on the niobium content than on the electrical conductivity. The reversible capacity in the 2-V region is mainly attributable to redox reactions involving rather sulfur than tin. |
Atsushi Sakuda, Koji Ohara, Katsutoshi Fukuda, Koji Nakanishi, Tomoya Kawaguchi, Hajime Arai, Yoshiharu Uchimoto, Toshiaki Ohta, Eiichiro Matsubara, Zempachi Ogumi, Toyoki Okumura, Hironori Kobayashi, Hiroyuki Kageyama, Masahiro Shikano, Hikari Sakaebe, Tomonari Takeuchi Amorphous Metal Polysulfides: Electrode Materials with Unique Insertion/Extraction Reactions Journal Article J. Am. Chem. Soc., 139 (26), pp. 8796–8799, 2017, ISSN: 0002-7863. @article{Sakuda2017a, title = {Amorphous Metal Polysulfides: Electrode Materials with Unique Insertion/Extraction Reactions}, author = {Atsushi Sakuda and Koji Ohara and Katsutoshi Fukuda and Koji Nakanishi and Tomoya Kawaguchi and Hajime Arai and Yoshiharu Uchimoto and Toshiaki Ohta and Eiichiro Matsubara and Zempachi Ogumi and Toyoki Okumura and Hironori Kobayashi and Hiroyuki Kageyama and Masahiro Shikano and Hikari Sakaebe and Tomonari Takeuchi}, url = {http://pubs.acs.org/doi/abs/10.1021/jacs.7b03909}, doi = {10.1021/jacs.7b03909}, issn = {0002-7863}, year = {2017}, date = {2017-07-01}, journal = {J. Am. Chem. Soc.}, volume = {139}, number = {26}, pages = {8796--8799}, abstract = {A unique charge/discharge mechanism of amorphous TiS_{4} is reported. Amorphous transition metal polysulfide electrodes exhibit anomalous charge/discharge performance and should have a unique charge/discharge mechanism: neither the typical intercalation/deintercala- tion mechanism nor the conversion-type one, but a mixture of the two. Analyzing the mechanism of such electrodes has been a challenge because fewer tools are available to examine the “amorphous” structure. It is revealed that the electrode undergoes two distinct structural changes: (i) the deformation and formation of S−S disulfide bonds and (ii) changes in the coordination number of titanium. These structural changes proceed continuously and concertedly for Li insertion/extraction. The results of this study provide a novel and unique model of amorphous electrode materials with significantly larger capacities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A unique charge/discharge mechanism of amorphous TiS4 is reported. Amorphous transition metal polysulfide electrodes exhibit anomalous charge/discharge performance and should have a unique charge/discharge mechanism: neither the typical intercalation/deintercala- tion mechanism nor the conversion-type one, but a mixture of the two. Analyzing the mechanism of such electrodes has been a challenge because fewer tools are available to examine the “amorphous” structure. It is revealed that the electrode undergoes two distinct structural changes: (i) the deformation and formation of S−S disulfide bonds and (ii) changes in the coordination number of titanium. These structural changes proceed continuously and concertedly for Li insertion/extraction. The results of this study provide a novel and unique model of amorphous electrode materials with significantly larger capacities. |
Tomoya Kawaguchi, Katsutoshi Fukuda, Eiichiro Matsubara Site- and Phase-Selective X-ray Absorption Spectroscopy Based on Phase-Retrieval Calculation Journal Article J. Phys. Condens. Matter, 29 (11), pp. 113002, 2017, ISSN: 0953-8984. @article{Kawaguchi2017, title = {Site- and Phase-Selective X-ray Absorption Spectroscopy Based on Phase-Retrieval Calculation}, author = {Tomoya Kawaguchi and Katsutoshi Fukuda and Eiichiro Matsubara}, url = {http://stacks.iop.org/0953-8984/29/i=11/a=113002?key=crossref.5e311d4db6feaedb90887256cf533e5d}, doi = {10.1088/1361-648X/aa53bb}, issn = {0953-8984}, year = {2017}, date = {2017-03-01}, journal = {J. Phys. Condens. Matter}, volume = {29}, number = {11}, pages = {113002}, publisher = {IOP Publishing}, abstract = {Understanding the chemical state of a particular element with multiple crystallographic sites and/or phases is essential to unlocking the origin of material properties. To this end, resonant x-ray diffraction spectroscopy (RXDS) achieved through a combination of x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques can allow for the measurement of diffraction anomalous fine structure (DAFS). This is expected to provide a peerless tool for electronic/local structural analyses of materials with complicated structures thanks to its capability to extract spectroscopic information about a given element at each crystallographic site and/or phase. At present, one of the major challenges for the practical application of RXDS is the rigorous determination of resonant terms from observed DAFS, as this requires somehow determining the phase change in the elastic scattering around the absorption edge from the scattering intensity. This is widely known in the field of XRD as the phase problem. The present review describes the basics of this problem, including the relevant background and theory for DAFS and a guide to a newly-developed phase-retrieval method based on the logarithmic dispersion relation that makes it possible to analyze DAFS without suffering from the intrinsic ambiguities of conventional iterative-fitting. Several matters relating to data collection and correction of RXDS are also covered, with a final emphasis on the great potential of powder-sample-based RXDS (P-RXDS) to be used in various applications relevant to practical materials, including antisite-defect-type electrode materials for lithium-ion batteries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Understanding the chemical state of a particular element with multiple crystallographic sites and/or phases is essential to unlocking the origin of material properties. To this end, resonant x-ray diffraction spectroscopy (RXDS) achieved through a combination of x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques can allow for the measurement of diffraction anomalous fine structure (DAFS). This is expected to provide a peerless tool for electronic/local structural analyses of materials with complicated structures thanks to its capability to extract spectroscopic information about a given element at each crystallographic site and/or phase. At present, one of the major challenges for the practical application of RXDS is the rigorous determination of resonant terms from observed DAFS, as this requires somehow determining the phase change in the elastic scattering around the absorption edge from the scattering intensity. This is widely known in the field of XRD as the phase problem. The present review describes the basics of this problem, including the relevant background and theory for DAFS and a guide to a newly-developed phase-retrieval method based on the logarithmic dispersion relation that makes it possible to analyze DAFS without suffering from the intrinsic ambiguities of conventional iterative-fitting. Several matters relating to data collection and correction of RXDS are also covered, with a final emphasis on the great potential of powder-sample-based RXDS (P-RXDS) to be used in various applications relevant to practical materials, including antisite-defect-type electrode materials for lithium-ion batteries. |
2016 |
Ikuma Takahashi, Katsutoshi Fukuda, Tomoya Kawaguchi, Hideyuki Komatsu, Masatsugu Oishi, Haruno Murayama, Masaharu Hatano, Takayuki Terai, Hajime Arai, Yoshiharu Uchimoto, Eiichiro Matsubara J. Phys. Chem. C, 120 (48), pp. 27109–27116, 2016, ISSN: 1932-7447. @article{Takahashi2016, title = {Quantitative Analysis of Transition-Metal Migration Induced Electrochemically in Lithium-Rich Layered Oxide Cathode and Its Contribution to Properties at High and Low Temperatures}, author = {Ikuma Takahashi and Katsutoshi Fukuda and Tomoya Kawaguchi and Hideyuki Komatsu and Masatsugu Oishi and Haruno Murayama and Masaharu Hatano and Takayuki Terai and Hajime Arai and Yoshiharu Uchimoto and Eiichiro Matsubara}, url = {http://pubs.acs.org/doi/10.1021/acs.jpcc.6b08199}, doi = {10.1021/acs.jpcc.6b08199}, issn = {1932-7447}, year = {2016}, date = {2016-12-01}, journal = {J. Phys. Chem. C}, volume = {120}, number = {48}, pages = {27109--27116}, abstract = {Lithium-rich layered oxides (LLOs) have attracted much attention as high-capacity electrodes in lithium-ion batteries. Especially, LLOs are known to show high performance at high temperature. The transition metal (TM) migrates from the TM layer to the Li layer in the LLO active material during the charge–discharge cycle, which complicates our understanding of its electrochemical properties. In this study, we applied X-ray diffraction spectroscopy (XDS) for acquiring quantitative data on TM migration depending on the crystallographic site in Li_{1.2–\textit{x}}Ni_{0.13}Co_{0.13}Mn_{0.53}O_{2}, and we discuss their influence on the electrochemical properties at 40 and −10 °C. The XDS analysis shows that both Mn and Ni in the TM layer migrate to the Li layer during the charge process and return during the discharge process. This reversible migration, observed at 40 °C, corresponds to a high capacity. On the other hand, the operation at −10 °C decreases the degree of TM migration as well as the charge–discharge capacity. In particular, Mn and Ni hardly migrate to the TM layer and remain at the Li layer at the end of discharge. This clogged interlayer space, which would lower the Li^{+} diffusion, accounts for the capacity drop.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lithium-rich layered oxides (LLOs) have attracted much attention as high-capacity electrodes in lithium-ion batteries. Especially, LLOs are known to show high performance at high temperature. The transition metal (TM) migrates from the TM layer to the Li layer in the LLO active material during the charge–discharge cycle, which complicates our understanding of its electrochemical properties. In this study, we applied X-ray diffraction spectroscopy (XDS) for acquiring quantitative data on TM migration depending on the crystallographic site in Li1.2–xNi0.13Co0.13Mn0.53O2, and we discuss their influence on the electrochemical properties at 40 and −10 °C. The XDS analysis shows that both Mn and Ni in the TM layer migrate to the Li layer during the charge process and return during the discharge process. This reversible migration, observed at 40 °C, corresponds to a high capacity. On the other hand, the operation at −10 °C decreases the degree of TM migration as well as the charge–discharge capacity. In particular, Mn and Ni hardly migrate to the TM layer and remain at the Li layer at the end of discharge. This clogged interlayer space, which would lower the Li+ diffusion, accounts for the capacity drop. |
E Matsubara, S Okada, T Ichitsubo, T Kawaguchi, A Hirata, P F Guan, K Tokuda, K Tanimura, T Matsunaga, M W Chen, N Yamada Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials Journal Article Phys. Rev. Lett., 117 (13), pp. 135501, 2016, ISSN: 0031-9007. @article{Matsubara2016, title = {Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials}, author = {E Matsubara and S Okada and T Ichitsubo and T Kawaguchi and A Hirata and P F Guan and K Tokuda and K Tanimura and T Matsunaga and M W Chen and N Yamada}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.117.135501}, doi = {10.1103/PhysRevLett.117.135501}, issn = {0031-9007}, year = {2016}, date = {2016-09-01}, journal = {Phys. Rev. Lett.}, volume = {117}, number = {13}, pages = {135501}, publisher = {American Physical Society}, abstract = {Despite the fact that phase-change materials are widely used for data storage, no consensus exists on the unique mechanism of their ultrafast phase change and its accompanied large and rapid optical change. By using the pump-probe observation method combining a femtosecond optical laser and an X-ray free- electron laser, we substantiate experimentally that, in both GeTe and Ge_{2}Sb_{2}Te_{5} crystals, rattling motion of mainly Ge atoms takes place with keeping the off-center position just after femtosecond-optical-laser irradiation, which eventually leads to a higher symmetry or disordered state. This very initial rattling motion in the undistorted lattice can be related to instantaneous optical change due to the loss of resonant bonding that characterizes GeTe-based phase change materials. Based on the amorphous structure derived by first-principles molecular dynamics simulation, we infer a plausible ultrafast amorphization mechanism via nonmelting.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Despite the fact that phase-change materials are widely used for data storage, no consensus exists on the unique mechanism of their ultrafast phase change and its accompanied large and rapid optical change. By using the pump-probe observation method combining a femtosecond optical laser and an X-ray free- electron laser, we substantiate experimentally that, in both GeTe and Ge2Sb2Te5 crystals, rattling motion of mainly Ge atoms takes place with keeping the off-center position just after femtosecond-optical-laser irradiation, which eventually leads to a higher symmetry or disordered state. This very initial rattling motion in the undistorted lattice can be related to instantaneous optical change due to the loss of resonant bonding that characterizes GeTe-based phase change materials. Based on the amorphous structure derived by first-principles molecular dynamics simulation, we infer a plausible ultrafast amorphization mechanism via nonmelting. |
2015 |
Shinya Okamoto, Tetsu Ichitsubo, Tomoya Kawaguchi, Yu Kumagai, Fumiyasu Oba, Shunsuke Yagi, Kohei Shimokawa, Natsumi Goto, Takayuki Doi, Eiichiro Matsubara Intercalation and Push-Out Process with Spinel-to-Rocksalt Transition on Mg Insertion into Spinel Oxides in Magnesium Batteries Journal Article Adv. Sci., 2 (8), pp. 1500072, 2015, ISSN: 21983844. @article{Okamoto2015, title = {Intercalation and Push-Out Process with Spinel-to-Rocksalt Transition on Mg Insertion into Spinel Oxides in Magnesium Batteries}, author = {Shinya Okamoto and Tetsu Ichitsubo and Tomoya Kawaguchi and Yu Kumagai and Fumiyasu Oba and Shunsuke Yagi and Kohei Shimokawa and Natsumi Goto and Takayuki Doi and Eiichiro Matsubara}, url = {http://doi.wiley.com/10.1002/advs.201500072}, doi = {10.1002/advs.201500072}, issn = {21983844}, year = {2015}, date = {2015-08-01}, journal = {Adv. Sci.}, volume = {2}, number = {8}, pages = {1500072}, abstract = {On the basis of the similarity between spinel and rocksalt structures, it is shown that some spinel oxides (e.g., MgCo_{2}O_{4}, etc) can be cathode materials for Mg rechargeable batteries around 150 °C. The Mg insertion into spinel lattices occurs via “intercalation and push-out” process to form a rocksalt phase in the spinel mother phase. For example, by utilizing the valence change from Co(III) to Co(II) in MgCo_{2}O_{4}, Mg insertion occurs at a considerably high potential of about 2.9 V vs. Mg^{2+}/Mg, and similarly it occurs around 2.3 V vs. Mg^{2+}/Mg with the valence change from Mn(III) to Mn(II) in MgMn_{2}O_{4}, being comparable to the \textit{ab initio} calculation. The feasibility of Mg insertion would depend on the phase stability of the counterpart rocksalt XO of MgO in Mg_{2}\textit{X}_{2}O_{4} or Mg\textit{X}_{3}O_{4} (\textit{X} = Co, Fe, Mn, and Cr). In addition, the normal spinel MgMn_{2}O_{4} and MgCr_{2}O_{4} can be demagnesiated to some extent owing to the robust host structure of Mg_{1−\textit{x}}\textit{X}_{2}O_{4}, where the Mg extraction/insertion potentials for MgMn_{2}O_{4} and MgCr_{2}O_{4} are both about 3.4 V vs. Mg^{2+}/Mg. Especially, the former “intercalation and push-out” process would provide a safe and stable design of cathode materials for polyvalent cations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } On the basis of the similarity between spinel and rocksalt structures, it is shown that some spinel oxides (e.g., MgCo2O4, etc) can be cathode materials for Mg rechargeable batteries around 150 °C. The Mg insertion into spinel lattices occurs via “intercalation and push-out” process to form a rocksalt phase in the spinel mother phase. For example, by utilizing the valence change from Co(III) to Co(II) in MgCo2O4, Mg insertion occurs at a considerably high potential of about 2.9 V vs. Mg2+/Mg, and similarly it occurs around 2.3 V vs. Mg2+/Mg with the valence change from Mn(III) to Mn(II) in MgMn2O4, being comparable to the ab initio calculation. The feasibility of Mg insertion would depend on the phase stability of the counterpart rocksalt XO of MgO in Mg2X2O4 or MgX3O4 (X = Co, Fe, Mn, and Cr). In addition, the normal spinel MgMn2O4 and MgCr2O4 can be demagnesiated to some extent owing to the robust host structure of Mg1−xX2O4, where the Mg extraction/insertion potentials for MgMn2O4 and MgCr2O4 are both about 3.4 V vs. Mg2+/Mg. Especially, the former “intercalation and push-out” process would provide a safe and stable design of cathode materials for polyvalent cations. |
Tomoya Kawaguchi, Katsutoshi Fukuda, Kazuya Tokuda, Masashi Sakaida, Tetsu Ichitsubo, Masatsugu Oishi, Jun'ichiro Mizuki, Eiichiro Matsubara Roles of Transition Metals Interchanging with Lithium in Electrode Materials Journal Article Phys. Chem. Chem. Phys., 17 (21), pp. 14064–70, 2015, ISSN: 1463-9084. @article{Kawaguchi2015a, title = {Roles of Transition Metals Interchanging with Lithium in Electrode Materials}, author = {Tomoya Kawaguchi and Katsutoshi Fukuda and Kazuya Tokuda and Masashi Sakaida and Tetsu Ichitsubo and Masatsugu Oishi and Jun'ichiro Mizuki and Eiichiro Matsubara}, url = {http://pubs.rsc.org/en/content/articlehtml/2015/cp/c5cp00940e}, doi = {10.1039/c5cp00940e}, issn = {1463-9084}, year = {2015}, date = {2015-06-01}, journal = {Phys. Chem. Chem. Phys.}, volume = {17}, number = {21}, pages = {14064--70}, publisher = {The Royal Society of Chemistry}, abstract = {Roles of antisite transition metals interchanging with Li atoms in electrode materials of Li transition-metal complex oxides were clarified using a newly developed direct labeling method, termed powder diffraction anomalous fine structure (P-DAFS) near the Ni K-edge. We site-selectively investigated the valence states and local structures of Ni in Li_{0.89}Ni_{1.11}O_{2}, where Ni atoms occupy mainly the NiO_{2} host-layer sites and partially the interlayer Li sites in-between the host layers, during electrochemical Li insertion/extraction in a lithium-ion battery (LIB). The site-selective X-ray near edge structure evaluated via the P-DAFS method revealed that the interlayer Ni atoms exhibited much lower electrochemical activity as compared to those at the host-layer site. Furthermore, the present analyses of site-selective extended X-ray absorption fine structure performed using the P-DAFS method indicates local structural changes around the residual Ni atoms at the interlayer space during the initial charge; it tends to gather to form rock-salt NiO-like domains around the interlayer Ni. The presence of the NiO-like domains in the interlayer space locally diminishes the interlayer distance and would yield strain energy because of the lattice mismatch, which retards the subsequent Li insertion both thermodynamically and kinetically. Such restrictions on the Li insertion inevitably make the NiO-like domains electrochemically inactive, resulting in an appreciable irreversible capacity after the initial charge but an achievement of robust linkage of neighboring NiO_{2} layers that tend to be dissociated without the Li occupation. The P-DAFS characterization of antisite transition metals interchanging with Li atoms complements the understanding of the detailed charge-compensation and degradation mechanisms in the electrode materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Roles of antisite transition metals interchanging with Li atoms in electrode materials of Li transition-metal complex oxides were clarified using a newly developed direct labeling method, termed powder diffraction anomalous fine structure (P-DAFS) near the Ni K-edge. We site-selectively investigated the valence states and local structures of Ni in Li0.89Ni1.11O2, where Ni atoms occupy mainly the NiO2 host-layer sites and partially the interlayer Li sites in-between the host layers, during electrochemical Li insertion/extraction in a lithium-ion battery (LIB). The site-selective X-ray near edge structure evaluated via the P-DAFS method revealed that the interlayer Ni atoms exhibited much lower electrochemical activity as compared to those at the host-layer site. Furthermore, the present analyses of site-selective extended X-ray absorption fine structure performed using the P-DAFS method indicates local structural changes around the residual Ni atoms at the interlayer space during the initial charge; it tends to gather to form rock-salt NiO-like domains around the interlayer Ni. The presence of the NiO-like domains in the interlayer space locally diminishes the interlayer distance and would yield strain energy because of the lattice mismatch, which retards the subsequent Li insertion both thermodynamically and kinetically. Such restrictions on the Li insertion inevitably make the NiO-like domains electrochemically inactive, resulting in an appreciable irreversible capacity after the initial charge but an achievement of robust linkage of neighboring NiO2 layers that tend to be dissociated without the Li occupation. The P-DAFS characterization of antisite transition metals interchanging with Li atoms complements the understanding of the detailed charge-compensation and degradation mechanisms in the electrode materials. |
Tetsu Ichitsubo, Shinya Okamoto, Tomoya Kawaguchi, Yu Kumagai, Fumiyasu Oba, Shunsuke Yagi, Natsumi Goto, Takayuki Doi, Eiichiro Matsubara Toward “Rocking-Chair Type” Mg–Li Dual-Salt Batteries Journal Article J. Mater. Chem. A, 3 (19), pp. 10188–10194, 2015, ISSN: 2050-7488. @article{Ichitsubo2015, title = {Toward “Rocking-Chair Type” Mg–Li Dual-Salt Batteries}, author = {Tetsu Ichitsubo and Shinya Okamoto and Tomoya Kawaguchi and Yu Kumagai and Fumiyasu Oba and Shunsuke Yagi and Natsumi Goto and Takayuki Doi and Eiichiro Matsubara}, url = {http://xlink.rsc.org/?DOI=C5TA01365H}, doi = {10.1039/C5TA01365H}, issn = {2050-7488}, year = {2015}, date = {2015-01-01}, journal = {J. Mater. Chem. A}, volume = {3}, number = {19}, pages = {10188--10194}, publisher = {Royal Society of Chemistry}, abstract = {High energy-density rechargeable batteries are strongly demanded from the viewpoint of energy and environmental concern. This work is devoted to fundamental electrochemistry on a novel concept of rechargeable batteries, “rocking-chair type” Mg–Li dual-salt batteries (DSBs), where both Mg and Li cations are carrier ions. In this system, dangerous dendritic growth is drastically suppressed by co-electro- deposition of Mg and Li, and Mg–Li alloys can be used as anode materials with high electrical capacities. As a DSB cathode material that can accommodate both Mg and Li cations, we use a spinel oxide MgCo_{2}O_{4}, in which an eccentric insertion mechanism, the “interca- lation & push-out” process, occurs. Mg insertion occurs at 2.9 V vs. Mg^{2+}/Mg and Li insertion occurs at 3.1 V vs. Li^{+}/Li, being consistent with \textit{ab initio } calculations, and its capacity approximately amounts to 150–200 mA h g^{-1}. In the combination of MgCo_{2}O_{4} and Mg_{50}Li_{50} alloys, the cell voltage during discharge is as high as about 2–3V. The concept of rocking-chair type DSB systems provides a new strategy for future safe rechargeable batteries combining high energy/power densities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } High energy-density rechargeable batteries are strongly demanded from the viewpoint of energy and environmental concern. This work is devoted to fundamental electrochemistry on a novel concept of rechargeable batteries, “rocking-chair type” Mg–Li dual-salt batteries (DSBs), where both Mg and Li cations are carrier ions. In this system, dangerous dendritic growth is drastically suppressed by co-electro- deposition of Mg and Li, and Mg–Li alloys can be used as anode materials with high electrical capacities. As a DSB cathode material that can accommodate both Mg and Li cations, we use a spinel oxide MgCo2O4, in which an eccentric insertion mechanism, the “interca- lation & push-out” process, occurs. Mg insertion occurs at 2.9 V vs. Mg2+/Mg and Li insertion occurs at 3.1 V vs. Li+/Li, being consistent with ab initio calculations, and its capacity approximately amounts to 150–200 mA h g-1. In the combination of MgCo2O4 and Mg50Li50 alloys, the cell voltage during discharge is as high as about 2–3V. The concept of rocking-chair type DSB systems provides a new strategy for future safe rechargeable batteries combining high energy/power densities. |
Tomoya Kawaguchi, Katsutoshi Fukuda, Tetsu Ichitsubo, Masatsugu Oishi, Jun'ichiro Mizuki, Eiichiro Matsubara Development of Powder Diffraction Anomalous Fine Structure Method and Applications to Electrode Materials for Rechargeable Batteries Journal Article J. Japanese Soc. Synchrotron Radiat. Res., 28 (3), pp. 124–134, 2015. @article{Kawaguchif, title = {Development of Powder Diffraction Anomalous Fine Structure Method and Applications to Electrode Materials for Rechargeable Batteries}, author = {Tomoya Kawaguchi and Katsutoshi Fukuda and Tetsu Ichitsubo and Masatsugu Oishi and Jun'ichiro Mizuki and Eiichiro Matsubara}, year = {2015}, date = {2015-01-01}, journal = {J. Japanese Soc. Synchrotron Radiat. Res.}, volume = {28}, number = {3}, pages = {124--134}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2014 |
Tomoya Kawaguchi, Koki Shimada, Tetsu Ichitsubo, Shunsuke Yagi, Eiichiro Matsubara J. Power Sources, 271 , pp. 431–436, 2014, ISSN: 03787753. @article{Kawaguchi2014a, title = {Surface-Layer Formation by Reductive Decomposition of LiPF_{6} at Relatively High Potentials on Negative Electrodes in Lithium Ion Batteries and its Suppression}, author = {Tomoya Kawaguchi and Koki Shimada and Tetsu Ichitsubo and Shunsuke Yagi and Eiichiro Matsubara}, url = {http://www.sciencedirect.com/science/article/pii/S0378775314012634}, doi = {10.1016/j.jpowsour.2014.08.010}, issn = {03787753}, year = {2014}, date = {2014-12-01}, journal = {J. Power Sources}, volume = {271}, pages = {431--436}, abstract = {In using a LiPF6/ethylene carbonate–dimethyl carbonate electrolyte for lithium ion batteries (LIBs), a certain reductive reaction is known to occur at a relatively high potential (ca. 2.6 V vs. Li^{+}/Li) on Sn electrode, but its details are still unknown. By means of in-situ X-ray reflectometry, X-ray photoelectron spectroscopy, scanning electron microscopy observations and electrochemical measurements (by using mainly Sn electrode, and additionally Pt, graphite electrodes), we have found out that this reduction eventually forms an inactive passivation-layer consisting mainly of insulative LiF ascribed to the reductive decomposition of LiPF_{6}, which significantly affects the battery cyclability. In contrast, a solid-electrolyte interphase (SEI) is formed by the reductive reaction of the solvent at ca. 1.5 V vs. Li^{+}/Li, which is lower than the reduction potential of LiPF_{6}. However, we have found that the formation of SEI preempts that of the passivation layer when holding the electrode at a potential lower than 1.5 V vs. Li^{+}/Li. Consequently, the cyclability is improved by suppressing the formation of the inactive passivation layer. Such a pretreatment would be quite effective on improvement of the battery cyclability, especially for a relatively noble electrode whose oxidation potential is between 1.5 V and 2.6 V vs. Li^{+}/Li.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In using a LiPF6/ethylene carbonate–dimethyl carbonate electrolyte for lithium ion batteries (LIBs), a certain reductive reaction is known to occur at a relatively high potential (ca. 2.6 V vs. Li+/Li) on Sn electrode, but its details are still unknown. By means of in-situ X-ray reflectometry, X-ray photoelectron spectroscopy, scanning electron microscopy observations and electrochemical measurements (by using mainly Sn electrode, and additionally Pt, graphite electrodes), we have found out that this reduction eventually forms an inactive passivation-layer consisting mainly of insulative LiF ascribed to the reductive decomposition of LiPF6, which significantly affects the battery cyclability. In contrast, a solid-electrolyte interphase (SEI) is formed by the reductive reaction of the solvent at ca. 1.5 V vs. Li+/Li, which is lower than the reduction potential of LiPF6. However, we have found that the formation of SEI preempts that of the passivation layer when holding the electrode at a potential lower than 1.5 V vs. Li+/Li. Consequently, the cyclability is improved by suppressing the formation of the inactive passivation layer. Such a pretreatment would be quite effective on improvement of the battery cyclability, especially for a relatively noble electrode whose oxidation potential is between 1.5 V and 2.6 V vs. Li+/Li. |
Shunsuke Yagi, Tetsu Ichitsubo, Yoshimasa Shirai, Shingo Yanai, Takayuki Doi, Kuniaki Murase, Eiichiro Matsubara A concept of dual-salt polyvalent-metal storage battery Journal Article J. Mater. Chem. A, 2 (4), pp. 1144–1149, 2014, ISSN: 2050-7488. @article{Yagi2014, title = {A concept of dual-salt polyvalent-metal storage battery}, author = {Shunsuke Yagi and Tetsu Ichitsubo and Yoshimasa Shirai and Shingo Yanai and Takayuki Doi and Kuniaki Murase and Eiichiro Matsubara}, url = {http://pubs.rsc.org/en/content/articlehtml/2014/ta/c3ta13668j}, doi = {10.1039/c3ta13668j}, issn = {2050-7488}, year = {2014}, date = {2014-12-01}, journal = {J. Mater. Chem. A}, volume = {2}, number = {4}, pages = {1144--1149}, publisher = {The Royal Society of Chemistry}, abstract = {In this work, we propose and examine a battery system with a new design concept. The battery consists of a non-noble polyvalent metal (such as Ca, Mg, Al) combined with a positive electrode already well-established for lithium ion batteries (LIBs). The prototype demonstrated here is composed of a Mg negative electrode, LiFePO4 positive electrode, and tetrahydrofuran solution of two kinds of salts (LiBF4 and phenylmagnesium chloride) as an electrolyte. The LIB positive-electrode materials such as LiFePO4 can preferentially accommodate Li+ ions; i.e., they work as a “Li pass filter”. This characteristic enables us to construct a septum-free, Daniel-battery type dual-salt polyvalent-metal storage battery (PSB). The presented dual-salt PSB combines many advantages, e.g., fast diffusion of Li+ ions in the positive electrode, high cyclability, and a high specific capacity of lightweight polyvalent metals. The concept is expected to allow the design of many combinations of dual-salt PSBs having a high energy density and high rate capability.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, we propose and examine a battery system with a new design concept. The battery consists of a non-noble polyvalent metal (such as Ca, Mg, Al) combined with a positive electrode already well-established for lithium ion batteries (LIBs). The prototype demonstrated here is composed of a Mg negative electrode, LiFePO4 positive electrode, and tetrahydrofuran solution of two kinds of salts (LiBF4 and phenylmagnesium chloride) as an electrolyte. The LIB positive-electrode materials such as LiFePO4 can preferentially accommodate Li+ ions; i.e., they work as a “Li pass filter”. This characteristic enables us to construct a septum-free, Daniel-battery type dual-salt polyvalent-metal storage battery (PSB). The presented dual-salt PSB combines many advantages, e.g., fast diffusion of Li+ ions in the positive electrode, high cyclability, and a high specific capacity of lightweight polyvalent metals. The concept is expected to allow the design of many combinations of dual-salt PSBs having a high energy density and high rate capability. |
T Kawaguchi, K Fukuda, K Tokuda, K Shimada, T Ichitsubo, M Oishi, J Mizuki, E Matsubara Revisit to Diffraction Anomalous Fine Structure. Journal Article J. Synchrotron Radiat., 21 (Pt 6), pp. 1247–51, 2014, ISSN: 1600-5775. @article{Kawaguchi2014b, title = {Revisit to Diffraction Anomalous Fine Structure.}, author = {T Kawaguchi and K Fukuda and K Tokuda and K Shimada and T Ichitsubo and M Oishi and J Mizuki and E Matsubara}, url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=4211131&tool=pmcentrez&rendertype=abstract}, doi = {10.1107/S1600577514015148}, issn = {1600-5775}, year = {2014}, date = {2014-11-01}, journal = {J. Synchrotron Radiat.}, volume = {21}, number = {Pt 6}, pages = {1247--51}, publisher = {International Union of Crystallography}, abstract = {The diffraction anomalous fine structure (DAFS) method that is a spectroscopic analysis combined with resonant X-ray diffraction enables the determination of the valence state and local structure of a selected element at a specific crystalline site and/or phase. This method has been improved by using a polycrystalline sample, channel-cut monochromator optics with an undulator synchrotron radiation source, an area detector and direct determination of resonant terms with a logarithmic dispersion relation. This study makes the DAFS method more convenient and saves a large amount of measurement time in comparison with the conventional DAFS method with a single crystal. The improved DAFS method has been applied to some model samples, Ni foil and Fe_{3}O_{4} powder, to demonstrate the validity of the measurement and the analysis of the present DAFS method.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The diffraction anomalous fine structure (DAFS) method that is a spectroscopic analysis combined with resonant X-ray diffraction enables the determination of the valence state and local structure of a selected element at a specific crystalline site and/or phase. This method has been improved by using a polycrystalline sample, channel-cut monochromator optics with an undulator synchrotron radiation source, an area detector and direct determination of resonant terms with a logarithmic dispersion relation. This study makes the DAFS method more convenient and saves a large amount of measurement time in comparison with the conventional DAFS method with a single crystal. The improved DAFS method has been applied to some model samples, Ni foil and Fe3O4 powder, to demonstrate the validity of the measurement and the analysis of the present DAFS method. |
Kazuya Tokuda, Tomoya Kawaguchi, Katsutoshi Fukuda, Tetsu Ichitsubo, Eiichiro Matsubara APL Mater., 2 (7), pp. 070701, 2014, ISSN: 2166-532X. @article{Tokuda2014, title = {Retardation and Acceleration of Phase Separation Evaluated from Observation of Imbalance between Structure and Valence in LiFePO_{4}/FePO_{4} Electrode}, author = {Kazuya Tokuda and Tomoya Kawaguchi and Katsutoshi Fukuda and Tetsu Ichitsubo and Eiichiro Matsubara}, url = {http://scitation.aip.org/content/aip/journal/aplmater/2/7/10.1063/1.4886555}, doi = {10.1063/1.4886555}, issn = {2166-532X}, year = {2014}, date = {2014-07-01}, journal = {APL Mater.}, volume = {2}, number = {7}, pages = {070701}, abstract = {LiFePO_{4} is a potential positive electrode material for lithium ion batteries. We have experimentally observed an imbalance between the valence change of Fe ions and the structure change from the LiFePO_{4} phase to the FePO_{4} phase during delithiation by simultaneous \textit{in situ} XRD and XANES measurements in an LiFePO_{4}/FePO_{4} electrode. The ratio of structure change to valence change clearly indicates that the phase separation from LiFePO_{4} to FePO_{4} is suppressed at the beginning of delithiation, while it is accelerated at the latter stage, which is due to the coherent strain caused by the lattice misfit between the two phases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } LiFePO4 is a potential positive electrode material for lithium ion batteries. We have experimentally observed an imbalance between the valence change of Fe ions and the structure change from the LiFePO4 phase to the FePO4 phase during delithiation by simultaneous in situ XRD and XANES measurements in an LiFePO4/FePO4 electrode. The ratio of structure change to valence change clearly indicates that the phase separation from LiFePO4 to FePO4 is suppressed at the beginning of delithiation, while it is accelerated at the latter stage, which is due to the coherent strain caused by the lattice misfit between the two phases. |
T Ichitsubo, S Yagi, R Nakamura, Y Ichikawa, S Okamoto, K Sugimura, T Kawaguchi, A Kitada, M Oishi, T Doi, E Matsubara A New Aspect of Chevrel Compounds as Positive Electrodes for Magnesium Batteries Journal Article J. Mater. Chem. A, 2 (36), pp. 14858, 2014, ISSN: 2050-7488. @article{Ichitsubo2014, title = {A New Aspect of Chevrel Compounds as Positive Electrodes for Magnesium Batteries}, author = {T Ichitsubo and S Yagi and R Nakamura and Y Ichikawa and S Okamoto and K Sugimura and T Kawaguchi and A Kitada and M Oishi and T Doi and E Matsubara}, url = {http://pubs.rsc.org/en/content/articlehtml/2014/ta/c4ta03063j}, doi = {10.1039/C4TA03063J}, issn = {2050-7488}, year = {2014}, date = {2014-07-01}, journal = {J. Mater. Chem. A}, volume = {2}, number = {36}, pages = {14858}, publisher = {The Royal Society of Chemistry}, abstract = {Chevrel compounds are regarded as potential positive-electrode materials for magnesium rechargeable batteries, but their redox potential is only about 1.2 V vs. Mg/Mg^{2+}. In this work, we show logically and experimentally that the redox potential of Chevrel compounds can be as high as about 2–3 V vs. Mg/Mg^{2+}. A crucial basis for this is that Cu cations can be extracted from Cu_{\textit{x}}Mo_{6}S_{8} at around 1.2–1.6 V vs. Mg/Mg^{2+} in the conventional electrolyte (Grignard-reagent/tetrahydrofuran) while the anodic dissolution of Cu metal can occur above about 1.7 V vs. Mg/Mg^{2+} in the same electrolyte, which means that the chemical potential of Cu in Chevrel compounds is higher than that in pure Cu metal. This thermodynamic conflict inevitably compels us to consider a certain interaction with the solvent, rather than simple deintercalation from the compound, which is discussed throughout the paper. With the use of large-molecule solvents or ionic liquids, we have observed an intriguing relaxation phenomenon, where the cations move to find more stable sites, which directly indicates that the Chevrel compounds have several sites for cations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Chevrel compounds are regarded as potential positive-electrode materials for magnesium rechargeable batteries, but their redox potential is only about 1.2 V vs. Mg/Mg2+. In this work, we show logically and experimentally that the redox potential of Chevrel compounds can be as high as about 2–3 V vs. Mg/Mg2+. A crucial basis for this is that Cu cations can be extracted from CuxMo6S8 at around 1.2–1.6 V vs. Mg/Mg2+ in the conventional electrolyte (Grignard-reagent/tetrahydrofuran) while the anodic dissolution of Cu metal can occur above about 1.7 V vs. Mg/Mg2+ in the same electrolyte, which means that the chemical potential of Cu in Chevrel compounds is higher than that in pure Cu metal. This thermodynamic conflict inevitably compels us to consider a certain interaction with the solvent, rather than simple deintercalation from the compound, which is discussed throughout the paper. With the use of large-molecule solvents or ionic liquids, we have observed an intriguing relaxation phenomenon, where the cations move to find more stable sites, which directly indicates that the Chevrel compounds have several sites for cations. |
Marcus C Newton, Mayu Sao, Yuta Fujisawa, Rena Onitsuka, Tomoya Kawaguchi, Kazuya Tokuda, Takahiro Sato, Tadashi Togashi, Makina Yabashi, Tetsuya Ishikawa, Tetsu Ichitsubo, Eiichiro Matsubara, Yoshihito Tanaka, Yoshinori Nishino Time-Resolved Coherent Diffraction of Ultrafast Structural Dynamics in a Single Nanowire Journal Article Nano Lett., 14 (5), pp. 2413–2418, 2014, ISSN: 1530-6992. @article{Newton2014, title = {Time-Resolved Coherent Diffraction of Ultrafast Structural Dynamics in a Single Nanowire}, author = {Marcus C Newton and Mayu Sao and Yuta Fujisawa and Rena Onitsuka and Tomoya Kawaguchi and Kazuya Tokuda and Takahiro Sato and Tadashi Togashi and Makina Yabashi and Tetsuya Ishikawa and Tetsu Ichitsubo and Eiichiro Matsubara and Yoshihito Tanaka and Yoshinori Nishino}, url = {http://dx.doi.org/10.1021/nl500072d}, doi = {10.1021/nl500072d}, issn = {1530-6992}, year = {2014}, date = {2014-04-01}, journal = {Nano Lett.}, volume = {14}, number = {5}, pages = {2413--2418}, publisher = {American Chemical Society}, abstract = {The continuing effort to utilize the unique properties present in a number of strongly correlated transition metal oxides for novel device applications has led to intense study of their transitional phase state behavior. Here we report on time-resolved coherent X-ray diffraction measurements on a single vanadium dioxide nanocrystal undergoing a solid-solid phase transition, using the SACLA X-ray Free Electron Laser (XFEL) facility. We observe an ultrafast transition from monoclinic to tetragonal crystal structure in a single vanadium dioxide nanocrystal. Our findings demonstrate that the structural change occurs in a number of distinct stages attributed to differing expansion modes of vanadium atom pairs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The continuing effort to utilize the unique properties present in a number of strongly correlated transition metal oxides for novel device applications has led to intense study of their transitional phase state behavior. Here we report on time-resolved coherent X-ray diffraction measurements on a single vanadium dioxide nanocrystal undergoing a solid-solid phase transition, using the SACLA X-ray Free Electron Laser (XFEL) facility. We observe an ultrafast transition from monoclinic to tetragonal crystal structure in a single vanadium dioxide nanocrystal. Our findings demonstrate that the structural change occurs in a number of distinct stages attributed to differing expansion modes of vanadium atom pairs. |
2013 |
Tetsu Ichitsubo, Takayuki Doi, Kazuya Tokuda, Eiichiro Matsubara, Tetsuya Kida, Tomoya Kawaguchi, Shunsuke Yagi, Shigeto Okada, Jun-ichi Yamaki What Determines the Critical Size for Phase Separation in LiFePO4 in Lithium Ion Batteries? Journal Article J. Mater. Chem. A, 1 (46), pp. 14532–14537, 2013, ISSN: 2050-7488. @article{Ichitsubo2013c, title = {What Determines the Critical Size for Phase Separation in LiFePO_{4} in Lithium Ion Batteries?}, author = {Tetsu Ichitsubo and Takayuki Doi and Kazuya Tokuda and Eiichiro Matsubara and Tetsuya Kida and Tomoya Kawaguchi and Shunsuke Yagi and Shigeto Okada and Jun-ichi Yamaki}, url = {http://pubs.rsc.org/en/Content/ArticleHTML/2013/TA/C3TA13122J}, doi = {10.1039/c3ta13122j}, issn = {2050-7488}, year = {2013}, date = {2013-11-01}, journal = {J. Mater. Chem. A}, volume = {1}, number = {46}, pages = {14532--14537}, publisher = {Royal Society of Chemistry}, abstract = {LiFePO_{4} characteristically shows a plateau voltage due to a two-phase (LiFePO_{4}/FePO_{4}) separation during the charge/discharge process in Li ion batteries. In this study, we clearly show that monodispersed nano- sized (about 10 nm) LiFePO_{4} particles exhibit a complete single-phase reaction without showing any plateau voltage. Since the elastic strain due to lattice mismatch between LiFePO_{4} and FePO_{4} would be easily released near the surface, elastic effects are usually expected to weaken, but, in contrast to this expectation, phase separation does not occur experimentally in such small nanoparticles. Consideration on the basis of only static thermodynamics is insufficient to explain why such a single-phase reaction occurs in nano-sized particles. In contrast, the mechanism of the single-phase reaction can be naturally understood, when we consider a kinetics concept based on the preferred wavelength for stable growth of the spinodal wave under such an elastic constraint.}, keywords = {}, pubstate = {published}, tppubtype = {article} } LiFePO4 characteristically shows a plateau voltage due to a two-phase (LiFePO4/FePO4) separation during the charge/discharge process in Li ion batteries. In this study, we clearly show that monodispersed nano- sized (about 10 nm) LiFePO4 particles exhibit a complete single-phase reaction without showing any plateau voltage. Since the elastic strain due to lattice mismatch between LiFePO4 and FePO4 would be easily released near the surface, elastic effects are usually expected to weaken, but, in contrast to this expectation, phase separation does not occur experimentally in such small nanoparticles. Consideration on the basis of only static thermodynamics is insufficient to explain why such a single-phase reaction occurs in nano-sized particles. In contrast, the mechanism of the single-phase reaction can be naturally understood, when we consider a kinetics concept based on the preferred wavelength for stable growth of the spinodal wave under such an elastic constraint. |
Koki Shimada, Tomoya Kawaguchi, Tetsu Ichitsubo, Eiichiro Matsubara, K Fukuda, Y Uchimoto, Z Ogumi In Situ Observation of Tin Negative Electrode / Electrolyte Interface by X-ray Reflectivity Journal Article ECS Trans., 50 (1), pp. 31–37, 2013, ISSN: 1938-6737. @article{Shimada, title = {In Situ Observation of Tin Negative Electrode / Electrolyte Interface by X-ray Reflectivity}, author = {Koki Shimada and Tomoya Kawaguchi and Tetsu Ichitsubo and Eiichiro Matsubara and K Fukuda and Y Uchimoto and Z Ogumi}, url = {http://ecst.ecsdl.org/content/50/1/31.full.pdf+html http://ecst.ecsdl.org/cgi/doi/10.1149/05001.0031ecst}, doi = {10.1149/05001.0031ecst}, issn = {1938-6737}, year = {2013}, date = {2013-03-01}, journal = {ECS Trans.}, volume = {50}, number = {1}, pages = {31--37}, abstract = {An electrode/electrolyte interface is obviously one of the most dominant factors controlling a battery performance. In the present work, a formation of a tin negative electrode/electrolyte interface (SEI) was investigated by an in situ X-ray reflectivity measurement. SEI was formed even at a high voltage of about 2.5 V vs Li/Li^{+}. This voltage is much higher than the value of about 1.5 V in the previous works. Thus, SEI in the present work is clearly different from that formed by reductive decomposition of an electrolyte and/or reduction of Sn oxide. Its structure was seemingly an amorphous solid containing a quite amount of fluoride, which grows up to 150-200 nm thick by keeping for 1 h at about 2.5-2.6 V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An electrode/electrolyte interface is obviously one of the most dominant factors controlling a battery performance. In the present work, a formation of a tin negative electrode/electrolyte interface (SEI) was investigated by an in situ X-ray reflectivity measurement. SEI was formed even at a high voltage of about 2.5 V vs Li/Li+. This voltage is much higher than the value of about 1.5 V in the previous works. Thus, SEI in the present work is clearly different from that formed by reductive decomposition of an electrolyte and/or reduction of Sn oxide. Its structure was seemingly an amorphous solid containing a quite amount of fluoride, which grows up to 150-200 nm thick by keeping for 1 h at about 2.5-2.6 V. |
Tetsu Ichitsubo, Kazuya Tokuda, Shunsuke Yagi, Makoto Kawamori, Tomoya Kawaguchi, Takayuki Doi, Masatsugu Oishi, Eiichiro Matsubara Elastically Constrained Phase-Separation Dynamics Competing with the Charge Process in the LiFePO4/FePO4 system Journal Article J. Mater. Chem. A, 1 (7), pp. 2567, 2013, ISSN: 2050-7488. @article{Ichitsubo2013, title = {Elastically Constrained Phase-Separation Dynamics Competing with the Charge Process in the LiFePO_{4}/FePO_{4} system}, author = {Tetsu Ichitsubo and Kazuya Tokuda and Shunsuke Yagi and Makoto Kawamori and Tomoya Kawaguchi and Takayuki Doi and Masatsugu Oishi and Eiichiro Matsubara}, url = {http://pubs.rsc.org/en/content/articlehtml/2013/ta/c2ta01102f http://xlink.rsc.org/?DOI=c2ta01102f}, doi = {10.1039/c2ta01102f}, issn = {2050-7488}, year = {2013}, date = {2013-01-01}, journal = {J. Mater. Chem. A}, volume = {1}, number = {7}, pages = {2567}, publisher = {The Royal Society of Chemistry}, abstract = {By using phase-field computer simulations, we have investigated the effects of the coherent strain due to the phase separation in the olivine-type LiFePO_{4}. In this system, the coherent elastic-strain energy due to the lattice mismatch between LiFePO_{4} and FePO_{4} phases accompanied by insertion and extraction of Li ions is considered to play a crucial role in the phase separation kinetics during the charge/discharge process. The present phase-field micromechanics simulations reveal several significant features of the LiFePO_{4}/FePO_{4} system accompanying the coherent strain, such as the retardation of the phase separation, the charge rate dependence, the thermodynamic stability of coherent interfaces between dual phases, etc. Nucleation of the new phase is found to be fundamentally unlikely in terms of the elastic strain energy, except in the vicinity of the surface of the particles, and thus the phase separation would be dominated by the spinodal decomposition process. When the nucleus is present precedently, however, the phase separation can proceed in the mixture mode of the domino cascade and spinodal decomposition processes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } By using phase-field computer simulations, we have investigated the effects of the coherent strain due to the phase separation in the olivine-type LiFePO4. In this system, the coherent elastic-strain energy due to the lattice mismatch between LiFePO4 and FePO4 phases accompanied by insertion and extraction of Li ions is considered to play a crucial role in the phase separation kinetics during the charge/discharge process. The present phase-field micromechanics simulations reveal several significant features of the LiFePO4/FePO4 system accompanying the coherent strain, such as the retardation of the phase separation, the charge rate dependence, the thermodynamic stability of coherent interfaces between dual phases, etc. Nucleation of the new phase is found to be fundamentally unlikely in terms of the elastic strain energy, except in the vicinity of the surface of the particles, and thus the phase separation would be dominated by the spinodal decomposition process. When the nucleus is present precedently, however, the phase separation can proceed in the mixture mode of the domino cascade and spinodal decomposition processes. |
Yoshihito Tanaka, Kiminori Ito, Marcus Newton, Takashi Nakatani, Rena Onitsuka, Isao Takahashi, Takahiro Sato, Tadashi Togashi, Makina Yabashi, Koki Shimada, Kazuya Tokuda, Tomoya Kawaguchi, Tetsu Ichitsubo, Eiichiro Matsubara, Yoshinori Nishino Time-Resolved Bragg Coherent X-ray Diffraction Study of Ultrafast Lattice Dynamics in Nano-Sized Thin Crystal by Using X-ray Free Electron Laser Journal Article J. Ceram. Soc. Japan, 121 (3), pp. 283–286, 2013. @article{Tanaka, title = {Time-Resolved Bragg Coherent X-ray Diffraction Study of Ultrafast Lattice Dynamics in Nano-Sized Thin Crystal by Using X-ray Free Electron Laser}, author = {Yoshihito Tanaka and Kiminori Ito and Marcus Newton and Takashi Nakatani and Rena Onitsuka and Isao Takahashi and Takahiro Sato and Tadashi Togashi and Makina Yabashi and Koki Shimada and Kazuya Tokuda and Tomoya Kawaguchi and Tetsu Ichitsubo and Eiichiro Matsubara and Yoshinori Nishino}, url = {https://www.jstage.jst.go.jp/article/jcersj2/121/1411/121_JCSJ-P12210/_article}, doi = {jcersj2.121.283}, year = {2013}, date = {2013-01-01}, journal = {J. Ceram. Soc. Japan}, volume = {121}, number = {3}, pages = {283--286}, abstract = {Ultrafast time-resolved Bragg coherent X-ray diffraction (CXD) has been performed for investigation of lattice dynamics in a nano-scale thin crystal by using a SASE (Self-Amplified Spontaneous Emission) –XFEL (X-ray Free Electron Laser), the name of which is SACLA. Single-shot Bragg diffraction pattern of a 100 nm-thick silicon crystal was obtained in the asymmetric configuration with a shallow reflection angle, in which an area detector shows the diffraction intensity distribution in the surface normal direction. By an optical femtosecond laser-pump and XFEL-probe method, the transient broadening of Bragg peak profile was observed at a delay time of around a few tens of picosecond, indicating the transient crystal lattice fluctuation induced by the optical laser. Perspective application of the time-resolved Bragg CXD method to small sized grains composing ceramic materials is discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ultrafast time-resolved Bragg coherent X-ray diffraction (CXD) has been performed for investigation of lattice dynamics in a nano-scale thin crystal by using a SASE (Self-Amplified Spontaneous Emission) –XFEL (X-ray Free Electron Laser), the name of which is SACLA. Single-shot Bragg diffraction pattern of a 100 nm-thick silicon crystal was obtained in the asymmetric configuration with a shallow reflection angle, in which an area detector shows the diffraction intensity distribution in the surface normal direction. By an optical femtosecond laser-pump and XFEL-probe method, the transient broadening of Bragg peak profile was observed at a delay time of around a few tens of picosecond, indicating the transient crystal lattice fluctuation induced by the optical laser. Perspective application of the time-resolved Bragg CXD method to small sized grains composing ceramic materials is discussed. |
2012 |
Tetsu Ichitsubo, Kazuya Tokuda, Tomoya Kawaguchi, Eiichiro Matsubara Elastic-Strain Influences on Electrode Potential and Charge/Discharge Dynamics in Electrode Active Materials for Storage Batteries Journal Article JSPS 172nd Comm. Alloy Phase Diagrams, 12 (1), pp. 76–87, 2012. @article{Ichitsubo2012a, title = {Elastic-Strain Influences on Electrode Potential and Charge/Discharge Dynamics in Electrode Active Materials for Storage Batteries}, author = {Tetsu Ichitsubo and Kazuya Tokuda and Tomoya Kawaguchi and Eiichiro Matsubara}, year = {2012}, date = {2012-01-01}, journal = {JSPS 172nd Comm. Alloy Phase Diagrams}, volume = {12}, number = {1}, pages = {76--87}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Book
2017 |
|
 | 日本XAFS研究会, (Ed.) XAFSの基礎と応用 Book 講談社サイエンティフィク, 2017, ISBN: 978-4-06-153295-3. @book{xafs_book1, title = {XAFSの基礎と応用}, editor = {日本XAFS研究会}, url = {https://www.kspub.co.jp/book/detail/1532953.html}, isbn = {978-4-06-153295-3}, year = {2017}, date = {2017-07-22}, publisher = {講談社サイエンティフィク}, abstract = {XAFSのバイブル、待望の改訂! 本書は2002年刊行『X線吸収分光法─XAFSとその応用』(太田俊明 編・アイピーシー刊)の全面改訂版です。旧版の良い点を受け継ぎ、新しい測定法や解析法を追加しました。 本書では、まず「第1章 序論」でXAFS研究、およびその関連研究分野がどのように発展してきたかを概説しました。 「第2章 XAFSの理論」では、EXAFSの理論について詳述しただけでなく、最近ますますその需要が増してきたXANESの理論を新たに付け加えました。 「第3章 XAFSの解析」では、一般的な解析法の説明に加え、解析法における諸問題をFAQの形で説明し、さらにXAFS解析に便利なソフトについての解説を加えました。また、実験家の立場からXANESの具体的な解釈についても新たに付け加えました。 「第4章 XAFS実験」では、放射光源、ビームライン、測定手法といった基盤技術に加えて、時間分解手法、空間分解手法、さらに、さまざまな分野への応用展開技術が最先端をいく研究者によって解説されています。旧版から最も大きく様変わりした章です。 「第5章 関連手法」では、XAFSに関連するさまざまな手法が紹介されています。XAFSはX線の吸収に起因する現象ですが、その中にはX線の散乱や干渉効果が含まれており、それは形を変えて非弾性散乱やDAFS(diffraction anomalous fine structure)などの現象としても現れます。 XAFSの理論・解析法はもちろん、放射光を利用した測定系や時間・空間分解測定、全反射測定、高圧下での測定、その場測定、界面や生体試料を対象とした測定まで、XAFSのすべてがわかる研究者必携の1冊です。}, keywords = {}, pubstate = {published}, tppubtype = {book} } XAFSのバイブル、待望の改訂! 本書は2002年刊行『X線吸収分光法─XAFSとその応用』(太田俊明 編・アイピーシー刊)の全面改訂版です。旧版の良い点を受け継ぎ、新しい測定法や解析法を追加しました。 本書では、まず「第1章 序論」でXAFS研究、およびその関連研究分野がどのように発展してきたかを概説しました。 「第2章 XAFSの理論」では、EXAFSの理論について詳述しただけでなく、最近ますますその需要が増してきたXANESの理論を新たに付け加えました。 「第3章 XAFSの解析」では、一般的な解析法の説明に加え、解析法における諸問題をFAQの形で説明し、さらにXAFS解析に便利なソフトについての解説を加えました。また、実験家の立場からXANESの具体的な解釈についても新たに付け加えました。 「第4章 XAFS実験」では、放射光源、ビームライン、測定手法といった基盤技術に加えて、時間分解手法、空間分解手法、さらに、さまざまな分野への応用展開技術が最先端をいく研究者によって解説されています。旧版から最も大きく様変わりした章です。 「第5章 関連手法」では、XAFSに関連するさまざまな手法が紹介されています。XAFSはX線の吸収に起因する現象ですが、その中にはX線の散乱や干渉効果が含まれており、それは形を変えて非弾性散乱やDAFS(diffraction anomalous fine structure)などの現象としても現れます。 XAFSの理論・解析法はもちろん、放射光を利用した測定系や時間・空間分解測定、全反射測定、高圧下での測定、その場測定、界面や生体試料を対象とした測定まで、XAFSのすべてがわかる研究者必携の1冊です。 |
Miscellaneous
2021 |
Kawaguchi, Tomoya; Ichitsubo, Tetsu 63 (2), pp. 151-158, Nihon Kessho Gakkaishi, 2021. @incollection{Kawaguchi2021c, title = {Experimental Methods of Bragg Coherent Diffraction Imaging for the 3D Displacement and Strain Field Visualization in Materials (Japanese review article)}, author = {Tomoya Kawaguchi and Tetsu Ichitsubo }, url = {https://www.jstage.jst.go.jp/article/jcrsj/63/2/63_151/_pdf/-char/ja}, doi = {https://doi.org/10.5940/jcrsj.63.151}, year = {2021}, date = {2021-06-02}, volume = {63}, number = {2}, pages = {151-158}, publisher = {Nihon Kessho Gakkaishi}, abstract = {Experimental methods of Bragg coherent diffraction imaging （BCDI） are briefly reviewed. BCDI has become an essential visualization technique that images the 3D displacement and strain field in the crystalline materials in situ. Nevertheless, the BCDI experiment is still not as common as the other conventional X-ray diffraction techniques presumably because of particular instrumentation utilizing delicate coherent X-ray optics and goniometer, which further requires a combination with the data reduction that reconstructs measured particle images during the experiment. Here, we briefly review the experimental methods of BCDI and its application to the alloy nanoparticles. We also discuss the advantages and challenges of BCDI as an analysis method and future perspectives.}, keywords = {}, pubstate = {published}, tppubtype = {incollection} } Experimental methods of Bragg coherent diffraction imaging （BCDI） are briefly reviewed. BCDI has become an essential visualization technique that images the 3D displacement and strain field in the crystalline materials in situ. Nevertheless, the BCDI experiment is still not as common as the other conventional X-ray diffraction techniques presumably because of particular instrumentation utilizing delicate coherent X-ray optics and goniometer, which further requires a combination with the data reduction that reconstructs measured particle images during the experiment. Here, we briefly review the experimental methods of BCDI and its application to the alloy nanoparticles. We also discuss the advantages and challenges of BCDI as an analysis method and future perspectives. |
Kawaguchi, Tomoya; Ichitsubo, Tetsu 63 (2), pp. 143-150, Nihon Kessho Gakkaishi, 2021. @incollection{Kawaguchi2021b, title = {Fundamental Concepts of Bragg Coherent Diffraction Imaging Enabling to Reveal the 3D Displacement and Strain Field in Materials (Japanese review article)}, author = {Tomoya Kawaguchi and Tetsu Ichitsubo}, url = {https://www.jstage.jst.go.jp/article/jcrsj/63/2/63_143/_pdf/-char/ja}, doi = {https://doi.org/10.5940/jcrsj.63.143}, year = {2021}, date = {2021-06-01}, volume = {63}, number = {2}, pages = {143-150}, publisher = {Nihon Kessho Gakkaishi}, abstract = {Fundamental concepts of Bragg coherent diffraction imaging （BCDI） are briefly reviewed. BCDI is increasingly popular for imaging crystalline nanoparticles under in-situ conditions. In contrast to the conventional coherent diffraction imaging （CDI） that measures a forward coherent scattering in a small angle region, BCDI is based on coherent Bragg diffraction from a crystalline sample for imaging, enabling us to observe the 3D minute displacement field of the lattice planes as well as the electron density of the particle, which provides new insight into the relationship between physical properties and lattice strain/defects.}, keywords = {}, pubstate = {published}, tppubtype = {incollection} } Fundamental concepts of Bragg coherent diffraction imaging （BCDI） are briefly reviewed. BCDI is increasingly popular for imaging crystalline nanoparticles under in-situ conditions. In contrast to the conventional coherent diffraction imaging （CDI） that measures a forward coherent scattering in a small angle region, BCDI is based on coherent Bragg diffraction from a crystalline sample for imaging, enabling us to observe the 3D minute displacement field of the lattice planes as well as the electron density of the particle, which provides new insight into the relationship between physical properties and lattice strain/defects. |
2019 |
Kawaguchi, Tomoya Travel memoir of studying abroad (Japanese) | 海外留学・滞在記 Incollection Denkikagaku, 87 (Winter), pp. 352-355, The electrochemical society of Japan, 2019. @incollection{Kawaguchi2019c, title = {Travel memoir of studying abroad (Japanese) | 海外留学・滞在記}, author = {Tomoya Kawaguchi}, url = {https://www.jstage.jst.go.jp/article/denkikagaku/87/Winter/87_19-OT0043/_pdf/-char/ja?fbclid=IwAR2M-EtijuxI6ScWDzTpcnTkEIVua14zp53tKEamonZ_ic_oUKaiub4kADY}, doi = {https://doi.org/10.5796/denkikagaku.19-OT0043}, year = {2019}, date = {2019-12-05}, booktitle = {Denkikagaku}, volume = {87}, number = {Winter}, pages = {352-355}, publisher = {The electrochemical society of Japan}, type = {memoir}, keywords = {}, pubstate = {published}, tppubtype = {incollection} } |
The last update: 11/18/2019