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論文

Effect of interlayer K ordering on water intercalation behavior in -type layered manganese dioxide

岡本範彦*; 吉迫大輝*; 市坪哲

Energy Storage Materials, 61, p.102912_1 - 102912_9, 2023/08

https://doi.org/10.1016/j.ensm.2023.102912

被引用回数：1 パーセンタイル：52.07(Chemistry, Physical)

Layered manganese dioxide (birnessite) that contains K cations and water molecules at interlayers exhibits reversible heat storage properties via a water-intercalation mechanism (0.5 mol H $_{2}$ O per K $_{0.33}$ MnO $_{2}$ ). However, a certain amount of an irreversible capacity of water intercalation is observed after the initial thermal cycle, which limits the reversibly available energy density of the material for the subsequent cycles. In this study, crystal structures of the K-containing birnessite, K $_{0.33}$ MnO $_{2}$ , was analyzed before and after heat treatment, by electron diffraction and atomic-resolution scanning transmission electron microscopy, to elucidate the origin of the initial irreversible capacity (0.83 mol per K $_{0.33}$ MnO $_{2}$ ).

論文

Optimizing LiMn $_{1.5}$ M $_{0.5}$ O $_{4}$ cathode materials for aqueous photo-rechargeable batteries

下川航平*; 松原翔吾*; 河口智也*; 岡本章玄*; 市坪哲

Chemical Communications, 59(51), p.7947 - 7950, 2023/06

https://doi.org/10.1039/D3CC01902K

被引用回数：0 パーセンタイル：0(Chemistry, Multidisciplinary)

Spinel oxides can be a promising high-potential cathode material of photo-rechargeable batteries. However, LiMn $_{1.5}$ M $_{0.5}$ O $_{4}$ (M = Mn) has a difficulty in a rapid degradation during charge/discharge under the illumination of UV-visible light. In this study, various spinel-oxide materials by modifying the composition (M = Fe, Co, Ni, Zn) were investigated to demonstrate photocharging in a water-in-salt aqueous electrolyte. LiMn $_{1.5}$ Fe $_{0.5}$ O $_{4}$ showed a substantially higher discharge capacity compared to that of LiMn $_{2}$ O $_{4}$ after long-term photocharging owing to enhanced stability under illumination. The result of this work provides fundamental design guidelines of spinel-oxide cathode materials to develop photo-rechargeable batteries.

論文

Mg-ion storage materials based on MnO $_{2}$ frameworks

下川航平*; 畠山拓也*; Li, H.*; 市坪哲

Current Opinion in Electrochemistry, 38, p.101209_1 - 101209_8, 2023/04

https://doi.org/10.1016/j.coelec.2023.101209

被引用回数：1 パーセンタイル：35.25(Chemistry, Physical)

A wide variety of crystal structures for MnO $_{2}$ is promising for basic frameworks of cathode materials in next-generation batteries such as Mg rechargeable batteries. In this short review, recent progress on MnO $_{2}$ -based cathode materials for Mg rechargeable batteries is summarized, especially focusing on the structures of the polymorphs, -MnO $_{2}$ and -MnO $_{2}$ , to discuss the criteria for achieving topotactic reactions during magnesiation.

論文

Mg-Zn-Mn oxide systems for a rechargeable Mg-battery cathode

Ye, X.*; 下川航平*; 毛塚有飛*; 畠山拓也*; Li, H.*; 市坪哲

Journal of Physical Chemistry C, 127(11), p.5210 - 5218, 2023/03

https://doi.org/10.1021/acs.jpcc.2c09071

被引用回数：1 パーセンタイル：52.07(Chemistry, Physical)

In this study, wide-range compositions in Mg-Zn-Mn oxide systems were investigated to understand its phase stability for the development of high-energy-density rechargeable Mg batteries. The obtained results showed that the stability of the spinel structure can be significantly improved by compositionally incorporating stable XO (X = Zn, Mg) with -MnO $_{2}$ . In particular, (i) the equimolar mixing of XO and MnO $_{2}$ is essential to obtain a single-phase cubic spinel structure and (ii) a higher Zn/Mg ratio is effective for preventing the formation of an irreversible rock salt phase to decrease the overpotential during discharge/charge cycling.

論文

Light-induced Li extraction from LiMn $_{2}$ O $_{4}$ /TiO $_{2}$ in a water-in-salt electrolyte for photo-rechargeable batteries

下川航平*; 松原翔吾*; 岡本章玄*; 市坪哲

Chemical Communications, 58(69), p.9634 - 9637, 2022/09

https://doi.org/10.1039/D2CC03362C

被引用回数：8 パーセンタイル：76.16(Chemistry, Multidisciplinary)

Photocharging of high-potential spinel LiMn $_{2}$ O $_{4}$ is demonstrated by using a water-in-salt electrolyte and TiO $_{2}$ nanoparticles. In a developed half-cell system with an electron acceptor, Li extraction from LiMn $_{2}$ O $_{4}$ proceeds under the illumination of UV-visible light at an estimated rate of c.a. 23 mA g $^{-1}$ . This work paves the way for highpotential cathode materials in photo-rechargeable batteries.

論文

Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎卓郎; Bae, J. W.*; et al.

Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02

https://doi.org/10.1016/j.actamat.2021.117571

被引用回数：59 パーセンタイル：99.75(Materials Science, Multidisciplinary)

Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.

口頭

原子力機構における原子力災害対応ロボット性能評価の標準試験法に関する検討

木村哲也*; 有井祥夫; 市坪浩二; 土田佳裕

no journal, ,

原子力機構における原子力災害対応ロボット性能評価の標準試験法開発について、原子力災害対応ロボット技術の認証制度検討会の検討状況を報告する。

口頭

ハイエントロピー合金FeCoNiCrPdにおけるCo NMR測定

中堂博之; 鈴木和也; 岡本範彦*; 市坪哲; 高梨弘毅

no journal, ,

ハイエントロピー合金(HEA)とは、5成分以上の元素を含み、主要元素が定まらないにも関わらず単相の不規則固溶体となる合金である。元素の組み合わせと混合割合の多さから、HEAには広大な物質探索領域があると期待され、精力的に研究されている。HEAには大きさの異なる多様な元素を固溶する性質があるため、格子ひずみが大きくなるということから主に構造材料としての性質が注目されている。また、磁気モーメントを持つ元素も固溶できることから磁気的性質も研究されており、バルク試料の帯磁率といった巨視的性質が測定されている。本研究では微視的測定手法である核磁気共鳴法(NMR)を用いて、等組成FeCoNiCrPdの多結晶試料におけるCo NMR測定を行い、当試料における固溶体の均一性を微視的に検証する。