論文 - 宇井 幸一
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溶融アルミニウムめっき鋼板のリチウムイオン二次電池用集電体としての可能性
小浦節子, 辻村太佳夫, 佐々木 悟, 阿部孝裕, 多田有矢, 工藤尚範, 齋藤良平, 内舘道正, 門磨義浩, 宇井幸一*
表面技術 67 ( 6 ) 316 - 321 2016年06月 [査読有り]
学術誌 共著・分担
For conventional organic electrolytes used in lithium-ion secondary batteries, we evaluated the electrochemical characteristics of hot-dipped aluminum (including 9 mass% silicon)-coated steel sheet, after rolling, as a current collector. Cyclic voltammograms clearly showed coupled redox peaks for potentials of 0–0.25 V (vs. Li/Li+). The redox peaks were attributed to reduction and oxidation reactions corresponding to insertion and extraction reactions of the Li+ ion into and from Al and Si. Oxidation current at higher potential was observed from about 3.25 V, indicating an electrochemical window of 3.00 V for potentials of 0.25–3.25 V. Subsequent EDX results revealed that the atomic concentration of Si in the aluminum layer decreased drastically after anodic polarization, suggesting the dissolution of Si. Using hot-dipped aluminum-coated steel sheet, after rolling, as a current collector for a positive electrode was inferred to be difficult. Using Li4Ti5O12 and a Li4.3Ti5O12 carbon composite negative electrode.
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Chih-Yao Chen, Teruki Sano, Tetsuya Tsuda*, Koichi Ui, Yoshifumi Oshima, Masaki Yamagata, Masashi Ishikawa, Masakazu Haruta, Takayuki Doi, Minoru Inaba, and Susumu Kuwabata
Scientific Reports 6 36153 2016年10月 [査読有り]
国際的学術誌 共著・分担
A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data.
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XAFS測定による高容量リチウム二次電池用正極材料の充放電サイクルに伴う放電電圧降下のメカニズム解析
武井悠記, 遠藤貴弘, 松友愛香莉, 渡辺 久, 門麿義浩, 宇井幸一
SPring-8利用研究成果集 ( 公益財団法人 高輝度光科学研究センター ) 6 ( 2 ) 270 - 276 2018年08月 [査読有り]
学術誌 共著・分担
固溶体正極材料aLi2MnO3-(1-a)Li(NixMnyCoz)O2 (x+y+z=1) (以下OLO と呼ぶ)の、長期充放電サイクルに伴う放電電圧の降下に関して、透過法と転換電子収量法を併用した解析手法によりバルクと表面近傍のどちらが起因しているかを特定することを目的としてXAFS 測定を行った。結果、長期充放電サイクルにおいて、Co よりもMn とNi 周りの局所構造が大きく変化しており、長期充放電サイクルに伴うMn およびNi を中心とした構造変化がΔV 現象の要因として考えられた。
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Removal of strontium from aqueous solutions using scallop shell powder
Fumihiro MIHARA, Yuta SHUSEKI, Sanae TAMURA, Koichi UI, Kenta KIKUCHI, Atsuo YASUMORI, Shinichi KOMABA, Mika FUKUNISHI, Yasuo KOGO, Yasushi IDEMOTO, Ken TAKEUCHI
Journal of the Ceramic Society of Japan ( 公益社団法人 日本セラミックス協会 ) 127 ( 2 ) 111 - 116 2019年02月 [査読有り]
学会誌 共著・分担
It is important to efficiently remove radioactive substances contained in polluted waters before they are discharged from nuclear power plants. In particular, there is an urgent need for the development of technology that can adsorb radioactive Sr2+, but there are currently no inexpensive Sr2+ adsorbents with low environmental burden. We found that scallop shell powder adsorbs Sr2+ in aqueous solutions at various initial concentrations. In this study, to obtain fundamental knowledge of the mechanism of Sr2+ removal using waste scallop shell, we analyzed the removability of Sr2+. Scallop shell showed the same capacity to remove Sr2+ at a high initial concentration (≥0.50 g/dm3) as the reagent CaCO3, but a clear difference in removability appeared at a low initial concentration (0.010 g/dm3), where scallop shell proved to be superior. In addition, scallop shell powder had slit-shaped pores and a specific surface area of 4.3 m2/g. Measurement of the adsorption isotherm in the low concentr
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Kazuma Honnami, Michiaki Matsukawa*, Tatsuya Senzaki, Tomoki Toyama, Haruka Taniguchi, Koichi Ui, Takahiko Sasaki, Kohki Takahashi, Makoto Hagiwara
Physica C: Superconductivity and its Applications 2021年04月 [査読有り]
学会誌 共著・分担
It is important to efficiently remove radioactive substances contained in polluted waters before they are discharged from nuclear power plants. In particular, there is an urgent need for the development of technology that can adsorb radioactive Sr2+, but there are currently no inexpensive Sr2+ adsorbents with low environmental burden. We found that scallop shell powder adsorbs Sr2+ in aqueous solutions at various initial concentrations. In this study, to obtain fundamental knowledge of the mechanism of Sr2+ removal using waste scallop shell, we analyzed the removability of Sr2+. Scallop shell showed the same capacity to remove Sr2+ at a high initial concentration (≥0.50 g/dm3) as the reagent CaCO3, but a clear difference in removability appeared at a low initial concentration (0.010 g/dm3), where scallop shell proved to be superior. In addition, scallop shell powder had slit-shaped pores and a specific surface area of 4.3 m2/g. Measurement of the adsorption isotherm in the low concentr
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Koichi Ui*, Satoshi Kobayashi, Kuniaki Sasaki, Tatsuya Takeguchi, Tetsuya Tsuda, Mikito Ueda, Jyunji Nunomura, Yukio Honkawa, and Yoichi Kojima
J. Electrochem. Soc. ( The Electrochemical Society ) 168 ( 5 ) 056510 2021年05月 [査読有り]
学術誌 共著・分担
The ionic liquid comprised of anhydrous aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) has attracted attention as an electrolyte for Al electrolysis. We have investigated the influence of the operating conditions on the deposition rate and the surface roughness of electrolytic Al foil by using the AlCl3-EMIC melt with/without 20 mmol dm−3 of an 1,10-phenanthroline anhydrate (OP) additive as the electrolyte. The cross-sectional SIM images revealed that the increase in the operating temperature affected the foil thickness and the OP addition affected the smoothness. At the operating temperature of 50 °C and the current density of 52.6 mA cm−2, the current efficiency was 90% or more and the deposition rate was about 0.9 μm min−1 regardless of the OP addition. An AFM image revealed that the surface roughness value of the Al foil obtained on the Ti plate substrate from the melt with the OP additive at 50 °C was 45.8 nm at the current density of 52.6 mA cm−2. The XRD patterns showed that the orientations of the (200) reflections became strong by the OP addition. A smooth Al foil was obtained even at a high current density by increasing the operating temperature and adding OP to the melt.
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Md. Mijanur Rahman *, Kenta Inaba, Garavdorj Batnyagt, Masato Saikawa, Yoshiki Kato, Rina Awata, Byambasuren Delgertsetsega, Yasuo Kaneta, Kotaro Higashi, Tomoya Uruga, Yasuhiro Iwasawa, Koichi Ui and Tatsuya Takeguchi *
RSC Advances ( Royal Society of Chemistry (United Kingdom) ) 11 20601 - 20611 2021年06月 [査読有り]
学術誌 共著・分担
Herein, we demonstrated that carbon-supported platinum (Pt/C) is a low-cost and high-performance electrocatalyst for polymer electrolyte fuel cells (PEFCs). The ethanol reduction method was used to prepare the Pt/C catalyst, which was realized by an effective matching of the carbon support and optimization of the Pt content for preparing a membrane electrode assembly (MEA). For this, the synthesis of Pt/C catalysts with different Pt loadings was performed on two different carbons (KB1600 and KB800) as new support materials. Analysis of the XRD pattern and TEM images showed that the Pt nanoparticles (NPs) with an average diameter of ca. 1.5 nm were uniformly dispersed on the carbon surface. To further confirm the size of the NPs, the coordination numbers of Pt derived from X-ray absorption fine structure (XAFS) data were used. These results suggest that the NP size is almost identical, irrespective of Pt loading. Nitrogen adsorption–desorption analysis indicated the presence of mesopores in each carbon. The BET surface area was found to increase with increasing Pt loading, and the value of the BET surface area was as high as 1286 m2 gcarbon−1. However, after 40 wt% Pt loading on both carbons, the BET surface area was decreased due to pore blockage by Pt NPs. The oxidation reduction reaction (ORR) activity for Pt/KB1600, Pt/KB800 and commercial Pt/C was evaluated by Koutecky–Levich (K–L) analysis, and the results showed first-order kinetics with ORR. The favourable surface properties of carbon produced Pt NPs with increased density, uniformity and small size, which led to a higher electrochemical surface area (ECSA). The ECSA value of the 35 wt% Pt/KB1600 catalyst was 155.0 m2 gpt−1 higher than that of the Pt/KB800 and commercial Pt/C (36.7 wt%) catalysts. A Higher ECSA indicates more available active sites for catalyst particles. The single cell test with MEA revealed that the cell voltage in the high current density regions depends on the BET surface area, and the durability of the 35 wt% Pt/KB1600 catalyst was superior to that of the 30 wt% Pt/KB800 and commercial Pt/C (46.2 wt%) catalysts. This suggests that an optimal ratio of Pt to Pt/KB1600 catalyst provides adequate reaction sites and mass transport, which is crucial to the PEFC's high performance.
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Koichi Ui*, Satoshi Kobayashi, Kuniaki Sasaki, Tatsuya Takeguchi, Tetsuya Tsuda, Mikito Ueda, Jyunji Nunomura, Yukio Honkawa, and Yoichi Kojima
UACJ Technical Reports ( 株式会社UACJ ) 10 ( 1 ) 31 - 39 2024年03月 [査読有り]
その他（含・紀要） 共著・分担
The ionic liquid comprised of anhydrous aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) has attracted attention as an electrolyte for Al electrolysis. We have investigated the influence of the operating conditions on the deposition rate and the surface roughness of electrolytic Al foil by using the AlCl3-EMIC melt with/without 20 mmol dm−3 of an 1,10-phenanthroline anhydrate (OP) additive as the electrolyte. The cross-sectional SIM images revealed that the increase in the operating temperature affected the foil thickness and the OP addition affected the smoothness. At the operating temperature of 50 °C and the current density of 52.6 mA cm−2, the current efficiency was 90% or more and the deposition rate was about 0.9 μm min−1 regardless of the OP addition. An AFM image revealed that the surface roughness value of the Al foil obtained on the Ti plate substrate from the melt with the OP additive at 50 °C was 45.8 nm at the current density of 52.6 mA cm−2. The XRD patterns showed that the orientations of the (200) reflections became strong by the OP addition. A smooth Al foil was obtained even at a high current density by increasing the operating temperature and adding OP to the melt.
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Electrochemical Characteristics of Lithium-Air Secondary Battery Using Amide-Based Ionic Liquids
Koichi UI *, Sota NAKAMURA, Yushi SATO, Tatsuya TAKEGUCHI, Masayuki ITAGAKI
Electrochemistry ( 公益社団法人電気化学会 ) 92 ( 4 ) 043010 2024年04月 [査読有り]
学術誌 共著・分担
Abstract
We fabricated lithium-air secondary batteries (LABs) employing amide-based ionic liquids (ILs) as electrolytes and evaluated their electrochemical characteristics. Lithium bis(trifluoromethanesulfonyl)amide (Li-TFSA) was employed as the lithium salt, N-methyl-N-propylpyrrolidinium-TFSA (Py13 system) with a cyclic aliphatic cation in the ILs, and N, N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium-TFSA (DEME system) with an acyclic aliphatic cation. The constant-current discharge-charge tests with the capacity controlled at 200 mAh (g-carbon)−1 showed that the overvoltage of the LABs using the Py13 system was lower than those of LABs using the DEME system and the organic solvent-based system electrolyte. The cycling performance of the DEME system rapidly decreased at the 74th cycle, while the Py13 system showed 200 mAh (g-carbon)−1 up to the 100th cycle, indicating a high stability. Electrochemical impedance measurements showed that the LABs using the Py13 system had the lowest interfacial resistance after the 1st charge. These results indicated that the use of the Py13 system with a relatively high electrical conductivity and low viscosity as the electrolyte would stabilize the cycling performance of the LABs. -
Koichi UI*, Ryohei HIBINO, Kuniaki SASAKI, Tatsuya TAKEGUCHI, Tetsuya TSUDA, Mikito UEDA, Junji NUNOMURA, Yoshihiko KYO, and Yoichi KOJIMA
Electrochemistry ( 公益社団法人電気化学会 ) 92 ( 8 ) 087006 2024年08月 [査読有り]
学術誌 共著・分担
Abstract
To investigate the feasibility of the electrorefining process for aluminum (Al) upgrade recycling, Al electrodeposition employing an ionic liquid consisting of anhydrous aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) was conducted. The effects of the operating temperature on the current efficiency, specific energy consumption, deposit properties, and deposition rate were investigated using the AlCl3-EMIC bath containing 1,10-phenanthroline anhydride (OP) as an additive at the current density of 100 mA cm−2. A constant-current electrodeposition showed that the specific energy consumption decreased to 5605 kWh t−1 at 80 °C with increasing the operating temperature in the OP-added bath and the current efficiency was over 90 % at the operating temperatures of 60–80 °C, but decreased to below 90 % at 90–100 °C. The cross-sectional ultra-low accelerating voltage scanning electron microscope (ULV-SEM) images showed the smoothness of the deposit obtained from the OP-added bath at 70 °C, but not at 90 °C. The XRD patterns of the Al deposits obtained from the OP-added bath showed a preferential orientation to the {100} plane at 60–80 °C, but almost no preferential orientation at 90–100 °C. It has been revealed that the improvement in the specific energy consumption requires an increase in the operating temperature, and that the surface roughness of the Al deposit must be improved by preferentially orienting the {100} plane in the texture to prevent any Al deposit from dropping out in order to improve the current efficiency at the cathode, which implies Al recovery.