論文 - 宇井 幸一
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AlCl3-BPC系溶融塩を電解液に用いる二次電池のAl負極構成材の検討
小浦延幸*, 津田英則, 宇井幸一
電気化学および工業物理化学 ( 公益社団法人 電気化学会 ) 64 ( 11 ) 1195 - 1199 1996年11月 [査読有り]
学術誌 共著・分担
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Koichi UI, Nobuyuki KOURA, Yasushi IDEMOTO*, and Kazutaka IIZUKA
Denki Kagaku (presently Electrochemistry) 65 ( 2 ) 161 - 162 1997年02月 [査読有り]
学術誌 共著・分担
1.381 2020 Journal Impact Factor (JIF)
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K+ -β- ferrite as a new cathode active material for lithium secondary battery
S. Ito*, K. Ui, N. Hoshi, H. Kurosawa, N. Koura, and K. Akashi
J. Phys. IV France 7 ( C1 ) 161 - 162 1997年05月 [査読有り]
その他（含・紀要） 共著・分担
The possibility of K+-β-ferrite (Kl.33Fe11O17) as a cathode active material for lithium secondary battery was investigated. It was confirmed that lithium ions certainly inserted into K+-β-ferrite. Li content y in LiyK1,33Fe11O17 was increased up to 6.79. Most of lithium ions seem to enter into γ-Fe2O3 layers of K+-β-ferrite, because alkali layers could contain only 2 alkali ions for Fe11O17. According to the cyclic voltammogram, good reversibility was observed in insertion and extraction of lithium ions. The discharge potential decreased to 1.5V vs. Li/Li+ and the charge potential increased to 4.5V vs. Li/Li+. The capacity of K+-β-ferrite has reached 200Ah/kg.
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不燃性常温型溶融塩電解液を用いるロッキングチェア型リチウム二次電池のLi-Al負極特性
小浦延幸, 宇井幸一
軽金属 47 ( 5 ) 267 - 272 1997年05月 [査読有り]
学術誌 共著・分担
The rocking chair type lithium secondary battery using an LiCl saturated AlCl3–1–ethyl–3–methylimidazolium chloride (EMIC) melt as a nonflammable electrolyte operated at room temperatures has been developed. LiCl was soluble in the acidic melts (50 mol%<AlCl3). In this study, Li metal was added to the melt in order to reduce Al2Cl7− remained in the melt to Al and AlCl4−. As a result, the potential window of the melt became about 4.4 V between the reduction potential of EMI+ and the oxidation potential of AlCl4−. Lithium was only deposited on an Al electrode from this melt. Cyclic voltammograms for an Al electrode in the melt showed reversible depositing and resolving behavior for lithium. From X-ray diffraction analysis, it was confirmed that Li–Al alloy was formed on the Al substrate at room temperature. Chronopotentiograms for an LixAl electrode in the melt showed ca. 280 Ah/kg of discharge capacity at the potential plateau range about −1.5 V vs. Al.
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不燃性常温型溶融塩電解液を用いるロッキングチェア型リチウム二次電池のV2O5正極特性
小浦延幸, 宇井幸一, 武石和之
軽金属 47 ( 5 ) 273 - 278 1997年05月 [査読有り]
学術誌 共著・分担
The rocking chair type lithium secondary battery using a nonflammable LiCl saturated AlCl3–1–ethyl–3–methylimidazolium chloride (EMIC) electrolyte operated at ambient temperatures has been developed. In this paper, the positive electrode (crystalline V2O5) characteristics and the discharge-charge cycle performance in this electrolyte were investigated. The content of the intercalated lithium in V2O5 and the structure of LixV2O5 were observed. As a result, the main reaction during the discharge-charge cycle was considered to be the intercalation and deintercalation reactions of lithium in the V2O5. When the discharge-charge cycle of the V2O5 electrode was performed, the life of the cycle ability was over more than 100. The nonflammable rocking chair type Li–Al¦LiCl saturated AlCl3–EMIC ¦ V2O5 secondary cell showed 3.2~2.0 V discharge voltage and 150 Ah/kg of discharge capacity.
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S. Ito, K. Ui, M. Ito, N. Koura, and K. Akashi
Journal of the Magnetics Society of Japan 22 ( 5 ) 449 - 451 1998年05月 [査読有り]
学術誌 共著・分担
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Lithium secondary battery using potassium -β- ferrite as a new cathode active material
S. Ito, K. Ui, N. Koura, and K. Akashi
Solid State Ionics 113-115 17 - 21 1998年11月 [査読有り]
学術誌 共著・分担
Lithium insertions into K+-β-ferrite (K1.4Fe11O17) were investigated by the ion exchange in the lithium salts and by the reduction of Fe3+ in a 1.6 M solution of n-butyl-lithium (BuLi) in hexane. Li0.4K0.9Fe11O17 with β-ferrite structure was obtained by soaking K+-β-ferrite powder in an LiCl n-hexyl alcohol solution at 150°C for 60 h. However, when the K+-β-ferrite powders were soaked in a molten salt of LiNO3 at 270 to 310°C for 20 h, the β-structures were destroyed. It is concluded that the lithium ions can be exchanged up to 0.4 with potassium ions in the alkali layers without destruction of the β-structure. Although the original K+-β-ferrite maintained β-structure at 1000°C, Li0.4K0.9Fe11O17 maintained β-structure up to 600°C. On the other hand, by soaking K1.4Fe11O17 in a BuLi at 25°C for 20 days, K1.2Li2.2Fe11O17 containing a large amount of lithium was obtained without destruction of the β-structure. This structure was not destroyed by heating the K1.2Li2.2Fe11O17 at 600°C. It is concluded that most of lithium ions are intercalated into the spinel blocks of β-ferrite. The results were compared to those of the electrochemical insertion.
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Nobuyuki KOURA, Kazutaka IIZUKA, Yasushi IDEMOTO, Koichi UI
Electrochemistry ( The Electrochemical Society of Japan ) 67 ( 6 ) 706 - 712 1999年06月 [査読有り]
学術誌 共著・分担
An AlCl3-1-ethyl-3-methylimidazolium chloride (EMIC) melt has a wide electrochemical window, and it is nonflammable with no ignition. We have developed the rocking chair type lithium secondary battery with an AlCl3-EMIC melt containing excess LiCl with a saturated solubility as the nonflammable electrolyte. In this paper, when LiCl was added in the acidic melt (AlCl3 > 50 mol %), the solubility of the LiCl and the changes in the physical properties were measured. Moreover, SOCl2 or Li metal was treated to completely remove any small amounts of Al2Cl7−, which was the ionic species for deposited Al, that remained in the melt. As a result, it was confirmed that Al2Cl7− was completely removed based on a cyclic voltammogram (C.V.) using a W electrode. The reversible deposition and dissolution behavior of lithium was indicated from the C.V. for a Li electrode in the SOCl2 containing melt, and it was found that a Li metal would perform as the negative electrode active material.
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小浦延幸, 對木洋文, 寺倉典宏, 井手本 康, 松本 太, 宇井幸一, 山田和夫, 見立武仁
表面技術 ( 一般社団法人 表面技術協会 ) 52 ( 1 ) 143 - 144 2001年01月 [査読有り]
学術誌 共著・分担
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小浦延幸, 府野真也, 對木洋文, 井手本 康, 宇井幸一, 松本 太
表面技術 ( 一般社団法人 表面技術協会 ) 53 ( 10 ) 683 - 687 2002年10月 [査読有り]
学術誌 共著・分担
The electrophoretic deposition of the artificial graphite particle, KS-25, on Cu foil has been examined in an acetonitrile bath containing additives such as triethylamine (TEA), tetramethylguanidine (TMG), and pyridine (Py). The charge-discharge capability of carbon anode for the Li-ion secondary battery prepared by the electrophoretic deposition method was estimated. Graphite particles were deposited electrophoretically on the anode substrate. The amount of graphite particle on Cu foil increased with an increasing deposition voltage, deposition time, and TEA concentration and was controllable in the range from 0 to 10mg·cm-2. The carbon anode provided relatively flat charge and discharge potentials (0 to 0.3V vs. Li/Li+) and high current capability (310mAh·g-1). Compared with the carbon anode composed of artificial graphite particles having a smaller grain size (KS-6), improvement in charge-discharge efficiency of the carbon anode with KS-25 particles was able to be observed in several of the early cycles. Moreover, the relationship between the ζ-potential and additive concentration, as well as the relationship between the amount of graphite particles deposited on Cu substrate and pKa of additives, and the results of the XPS measurement of graphite particle surface suggested that the charging of the graphite particle surface was caused by the deprotonation of carboxyl and alcohol groups by additives such as TEA, TMG, and Py.
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Bi1.76Pb0.44Sr1.86Ca2.08-xYxCu2.86Oy超伝導酸化物におけるTc, JcのY置換量、酸素量依存
井手本 康, 津之地洋平, 宇井幸一, 小浦延幸
日本セラミックス協会学術論文誌 ( 社団法人 日本セラミックス協会 ) 111 ( 10 ) 781 - 785 2003年10月 [査読有り]
学術誌 共著・分担
The purpose of this paper is to interpret the enhancement of Tc and Jc by the replacement of cations and changing the excess oxygen content for a Bi-2223 system by the replacement of Bi and Ca by Pb and Y, respectively, to form Bi1.76Pb0.44Sr1.86Ca2.08-xYxCu2.86Oy. The relation between lattice constant, average valences of Bi+Pb and Cu, excess oxygen content and superconducting characteristics has been studied as a function of Y substitution content, and anneal treatment. The highest Tc was obtained at x=0.05. Oxygen doped and overdoped regions and highest Tc(zero), which were obtained upon adjusting the optimum excess oxygen content, existed at each Y content, x=0-0.30. Furthermore, in order to elucidate the effect of metal substitution and oxygen content on Jc of a Bi-2223 system, films were prepared, which have the same metal composition of bulk, on a MgO(100) single crystal substrate by the spin coating-pyrolysis method. The measurements of Jc and Tc were carried out on highly oriented films of Bi-2223 phase with changing Y content. The highest Tc(zero) was obtained at Y content, x=0.05. Tc(zero) decreased with increasing x in the region of x>0.05. On the other hand, the highest Jc was obtained at x=0.10. The Y content for optimum Jc was different from that for optimum Tc. Jc increased with increasing excess oxygen content, Δy, and after that increase or constant in the oxygen overdoped region. Consequently, the metal and oxygen contents were very important for obtaining the highest Tc and Jc.
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Yasushi IDEMOTO*, Hiroshi SEKINE, Koichi UI, and Nobuyuki KOURA
Electrochemistry ( The Electrochemical Society of Japan ) 71 ( 12 ) 1142 - 1144 2003年12月 [査読有り]
学術誌 共著・分担
We investigated the crystal structure change during the charge-discharge process of LiMn1.5Ni0.5O4 as a 5 V class cathode active material, which was prepared by the sol-gel method. The lithium content of Li1−xMn1.5Ni0.5O4 (x = 0.5, 0.7, 1.0) was controlled by electrochemical lithium extraction. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. As a result, all samples consisted of three phases (space group: P4332) of different lattice constant and Ni valences. The each phase showed a different distortion of the Mn,Ni (12d)-O octahedral site and the Madelung energy.
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Yuka ITO, Yasushi IDEMOTO*, Koichi UI, Nobuyuki KOURA
Electrochemistry ( The Electrochemical Society of Japan ) 71 ( 12 ) 1145 - 1147 2003年12月 [査読有り]
学術誌 共著・分担
e investigated the electronic states of LiyMn2−xMxO4 (M = Mn, Mg, Ni, Co) as cathode active materials for the 4 V class lithium secondary battery. We calculated the electronic states of LiyMn1.75M0.25O4 (M = Mn; y = 0, Mg, Ni; y = 0.5, Co; y = 0.25) using first-principles calculations by the DV-Xα method. The net charge of each atom, and the bond overlap populations of Mn-O and M-O were calculated. The strong covalency between Mn and O existed in the Li defect model and LiyMn1.75M0.25O4 (M = Mg, Ni, Co). The bonding change in Mn-O is small and maintained the spinel structure during the charge-discharge process by substitution of Mn with M (= Mg, Ni, Co).
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Futoshi MATSUMOTO*, Masahiro HARADA, Nobuyuki KOURA, Yasushi IDEMOTO, Koichi UI
Electrochemistry ( The Electrochemical Society of Japan ) 72 ( 2 ) 103 - 110 2004年02月 [査読有り]
学術誌 共著・分担
Origin of enhanced electrochemical oxidation of glucose observed around 0.3 V (vs. Ag/AgCl (KCl sat.)) on an Hg adatom-modified Au polycrystalline electrode in alkaline aqueous solutions was investigated by cyclic voltammetry in various potential regions and solution pH's. The enhanced oxidation current was stable under continuous cycling between - 0.55 and 0.35 V. Positive scanning of potentials to greater than 0.35 V caused the oxidation current to decrease with dissolution of the UPD adlayer of Hg from the Au electrode. The surface structure of the Hg adatom-modified Au electrode found to be highly important in glucose oxidation. Moreover, pH dependence of the enhancement of glucose oxidation was attributed to the amount of adsorbed OH- on the Hg adatom-modified Au electrode. The investigation revealed that the surface structure on the Hg adatom-modified Au electrode cased an increase in the amount of adsorbed OH- on the Hg adatom-modified Au electrode around 0.35 V. It was considered that OHad produced by partial discharge of OH- on the Hg adatoms and/or oxide layer (Au(OHad)) of Au surface catalyzed the oxidation of glucose on the Hg adatom-modified Au electrode.
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Photocatalytic Activity of Ag-TiO2(anatase) Composite Film Prepared by Composite Coating
Fumio YAMAGUCHI, Tomohiro FUJITA, Yasuhiro KANEGA, Koichi UI, Yasushi IDEMOTO, Nobuyuki KOURA*
Electrochemistry ( The Electrochemical Society of Japan ) 72 ( 3 ) 156 - 158 2004年03月 [査読有り]
学術誌 共著・分担
The photocatalytic reaction with TiO2 particle using sunlight which decomposes various environmental pollutants has been studied extensively. This study considered the immobilization of the TiO2(A) particle on a brass substrate by a composite coating method. It was found that photocatalytic activity changed with differences in the immobilization metal (Ag, Ni, Pd, Cu)-TiO2(A) and the Ag-TiO2(A) composite film was shown the most remarkable photocatalytic activity.
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AlCl3-EMIC常温型溶融塩を用いたアルミニウム配向電析 －キシレン混合による配向性に及ぼす影響－
宇井幸一, 八代高士, 二村昌樹, 井手本 康, 小浦延幸
表面技術 ( 一般社団法人 表面技術協会 ) 55 ( 6 ) 409 - 416 2004年06月 [査読有り]
学術誌 共著・分担
An aluminum deposit oriented to a specific face is obtained from Lewis acidic aluminum chloride (AlCl3) 1-ethyl-3-methylimidazolium chloride (EMIC) ambient-temperature molten salt. We tried to stably produce the oriented deposit with a flat and smooth surface from the AlCl3-EMIC melt with xylene isomers added. Study of aluminum deposition from the xylene-added bath made it possible to investigate the mechanism of the oriented deposition.
Aluminum oriented to (110) was electrodeposited from the acidic melt with o-, p-xylene added. On the other hand, aluminum oriented to (100), which has never been obtained, was deposited from the melt with 50mol% m-xylene added after being aged four hours from the bath preparation. Moreover, the deposit had metallic luster. Using SEM, tried to find out the relation between the orientation and the metallic luster. The deposit with metallic luster had a very flat surface. The deposit without metallic luster had a textural structure. Furthermore, we observed the initial state of the deposit by the AFM technique. Prior nucleation took place in the case of the metallic deposit oriented to (100). Prior crystal grain growth took place in the case of the nonmetallic deposit oriented to (110). -
5V級Li二次電池用正極活物質LiMn1.5Ni0.5O4の合成条件による物性、結晶構造と電極特性の関係
井手本 康*, 関根 裕, 宇井幸一, 小浦延幸
Electrochemistry ( The Electrochemical Society of Japan ) 72 ( 8 ) 564 - 568 2004年08月 [査読有り]
学術誌 共著・分担
We investigated the physical property, crystal structure and electrode performance of LiMn1.5Ni0.5O4 as a 5 V class cathode active material, which was prepared by changing the calcined temperature with the sol-gel method. Cycle performance is different from the calcined temperature. LiMn1.5Ni0.5O4, which calcined at 700°C, showed a good cycle performance with the maximum discharge capacity of 125.3 mAh/g, and the capacity after 100 cycles was 95.1% of the maximum capacity. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. From a result, LiMn1.5Ni0.5O4, which calcined at 650°C, composed of mixing two space group P4332 phases. It is suggested that the oxidation states of Ni change in the sample, as these phases are different from each lattice parameter. Ni valence of sub-phase for LiMn1.5Ni0.5O4 calcined at 650°C, which was calculated from Bond Valence Sum, increase. Moreover, we investigated, the distortion and the stability of crystal structure by the bond length and the Madelung energy, nuclear and electron densities by MEM method with neutron diffraction and X-ray diffraction.
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Li二次電池正極材料LixMn2-yMyO4(M=Mg, Al, Cr, Mn)の熱力学安定性および結晶構造のLi量依存
井手本 康*, 堀子和孝, 宇井幸一, 小浦延幸
Electrochemistry ( The Electrochemical Society of Japan ) 72 ( 10 ) 680 - 687 2004年10月 [査読有り]
学術誌 共著・分担
We investigated the relation between the thermodynamic stability and crystal structure dependence of Li content for the substituted spinel, LixMn2-yMyO4 (M = Mg, Al, Cr, Mn). The enthalpy change per mole of atoms for the formation reaction, ΔHR, were calculated from the heat of dissolution. ΔHR increased with the decreasing Li content. ΔHR of the all amounts of Li content for LixMn2-yMyO4 (M = Mg, Al, Cr, Mn) decreased compared to that of LixMn2-yMyO4. The crystal structure analysis by powder neutron diffraction was examined for LixMn2-yMyO4 (M = Mg, Al, Cr, Mn). The Madelung energy increases with decreasing Li content for LixMn2O4, and it was associated with the thermodynamic data. From these results, the host structure is structurally and thermodynamically stable of the all amounts of Li content with the substitution of M for LixMn2-yMyO4.
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化学的に脱LiしたLi二次電池正極活物質LixMn2-yMyO4(M=Mg, Al, Cr, Mn, Co, Zn, Ni)の結晶構造、電子構造のLi量依存
井手本 康*, 堀子和孝, 伊藤由賀, 小浦延幸, 宇井幸一
Electrochemistry ( The Electrochemical Society of Japan ) 72 ( 11 ) 755 - 762 2004年11月 [査読有り]
学術誌 共著・分担
We investigated the crystal structure, electronic structure and nuclear state of chemical delithiated spinel LixMn2-yMyO4 (M = Mg, Al, Cr, Mn, Co, Zn, Ni) dependence Li content, x. We obtained the electronic and nuclear density distributions of the samples from XRD and neutron diffraction data using the maximum entropy method. Li content of LixMn2-yMyO4 was controlled by changing concentration of H2SO4-H2O aqueous solution. Mn valence increased and lattice parameter, a, decreased with decreasing Li content. The electron of Li0.095Mn2O4 was delcolization from the results of electronic density distribution. The amount of change of covalent bonding of (Mn, M)-O for LixMn2-yMyO4 (M = Mg, Al, Cr, Co, Zn, Ni) decreased in comparison with that of LixMn2O4 when Li content changed. From the results, the host structure is stable with the substitution of M for LixMn2-yMyO4.
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Bi4-x+yLaxTi3O12-d(x=0.5, y=0; x=0.75, y=0;x=0.75, y=0.15)強誘電体セラミックスの熱処理による強誘電特性への影響
井手本 康, 横山直人, 小浦延幸, 宇井幸一
日本セラミックス協会学術論文誌 ( 公益社団法人 日本セラミックス協会 ) 112 ( 12 ) 669 - 673 2004年12月 [査読有り]
学術誌 共著・分担
We investigated the effect of ferroelectric property on heat treatment at high oxygen partial pressure or vacuum for Bi4-x+yLaxTi3O12-δ (x=0.75, y=0; x=0.50, y=0; x=0.75, y=0.15). The remnant polarization (Pr) increases with increasing oxygen partial pressure during heat treatment. The coercive electric field (Ec) showed the same tendency as Pr at x=0.75 and y=0. In x=0.5 and y=0, Ec decreased with increasing oxygen partial pressure during heat treatment. Tc decreased by heat treatment under high oxygen partial pressure.
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Yasushi Idemoto *, Hiroshi Sekine, Koichi Ui, Nobuyuki Koura
Solid State Ionics ( Elsevier ) 176 ( 3-4 ) 299 - 306 2005年01月 [査読有り]
学術誌 共著・分担
We investigated the relation between the cycle performance and crystal structural change during the charge–discharge process of LiMn1.5Ni0.5O4 as a 5 V class cathode active material, which was prepared by changing the calcination temperature using the sol–gel method. The lithium content of Li1−xMn1.5Ni0.5O4 (x=0.5, 0.7, 1.0) was controlled by electrochemical lithium extraction. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. As a result, all samples consisted of three phases (space group: P4332) of different lattice constants and Ni valences. The main phase, which has the maximum percentage, was shifted to a phase with a lower lattice constant with the decreasing lithium content, and then finally Li1−xMn1.5Ni0.5O4 (x=1.0) was almost oxidized to Ni4+ by a charging process. Furthermore, LiMn1.5Ni0.5O4,, by changing the synthesis temperature, was different for a few oxidation processes; the structure of the phase at Ni3+ was not stable based on the distortion of each phase and the Madelung energy. It was suggested that these factors should provide an effective cycle performance.
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Bi2.20-zPbzSr1.86Ca2.03Y0.05Cu2.86Oy超伝導酸化物におけるTc, JcのPb置換量及び酸素量依存
井手本 康*, 津之地洋平, 宮部 徹, 宇井幸一, 小浦延幸
日本セラミックス協会学術論文誌 ( 公益社団法人 日本セラミックス協会 ) 113 ( 2 ) 166 - 171 2005年02月 [査読有り]
学術誌 共著・分担
The purpose of this paper is to interpret the enhancement of Tc and Jc by the replacement of cations and changing the excess oxygen content for Bi-2223 system by the replacement of Bi and Ca by Pb and Y, respectively, that is Bi2.20-zPbzSr1.86Ca2.03Y0.05Cu2.86Oy. The relations between lattice constant, average valences of Bi+Pb and Cu, excess oxygen content and superconducting characteristics have been studied by changing Pb substitution content, and annealing treatment. Bulk samples were prepared by the coprecipitation method. Furthermore, in order to elucidate the effect of metal substitution and oxygen content on Jc of the Bi-2223 system, films which have the same metal composition of the bulk, were prepared on MgO (100) single crystal substrate by the spin coating-pyrolysis method. Measurements of Jc and Tc were carried out on highly oriented films of Bi-2223 phase with changing Pb content and oxygen content: Tc (zero) experienced a maximum at Pb content, z=0.50 (nominal composition), and Tc (zero) decreased with increasing z in the region z>0.50. On the other hand, Jc also showed a maximum at z=0.50, but it was constant with increasing z in the region z>0.50. Oxygen underdoped and overdoped regions, and the highest Tc (zero) and Jc were obtained upon adjusting the optimum excess oxygen content, by changing Pb content and annealing treatment.
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Koichi UI*, Kohei ISHIKAWA, Takao FURUYA, Yasushi IDEMOTO, and Nobuyuki KOURA
Electrochemistry ( The Electrochemical Society of Japan ) 73 ( 2 ) 120 - 122 2005年02月 [査読有り]
学術誌 共著・分担
The positive electrode performance of the LiCoO2 electrode in the LiCl saturated AlCl3-1-ethyl-3-methylimizadolium chloride (EMIC) + SOCl2 melt as the electrolyte for nonflammable lithium secondary batteries was evaluated. In the cyclic voltammogram of the LiCoO2 electrode in the melt, the oxidation and reduction waves corresponding to the electrochemical intercalation / deintercalation reactions of Li+ were observed at 3.5~4.2 V vs. Li+/Li, and it suggested that the LiCoO2 electrode operated well in this melt. From charge and discharge evaluations, it was known that the discharge capacity was about 130 mAh g-1 and the coulomb efficiency was maintained of more than 93% during ten cycles. It became clear that the LiCoO2 electrode operates quite as a positive electrode in the melt.
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鉛蓄電池用負極集電体に用いるPb合金の充電状態における腐食挙動
小浦延幸*, 粕谷健太, 宇井幸一, 滝口友輝, 井手本 康
Electrochemistry ( The Electrochemical Society of Japan ) 73 ( 2 ) 135 - 140 2005年02月 [査読有り]
学術誌 共著・分担
The corrosion behavior of the exposed part of the Pb alloy negative electrode from the electrolyte was analyzed upon charging, i.e., under the reduced state. Dissolved oxygen in the electrolyte affected the generation rate and the grain size of the PbSO4. From the potential measurements at the exposed part, it was found that the part not under reducing conditions and the generation reaction of PbSO4 progressed by the Jocal cell reaction. Furthermore, when the dissolved oxygen concentration in the electrolyte film on the exposed part increased, the potential at the exposed part became noble and the PbSO4 generation rate increased. On the other hand, the most anti-corrosive Pb alloy was the Pb-1.8% Sn-0.03% Se alloy. The reason was attributed to the dense corrosion layer formed on the surface, because the PbSO4 grain size became small by the synergistic effect of Sn and Se.
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CuCl-1-ブチルピリジニウムクロリド常温型溶融塩中のCu(I)イオンからの高純度Cuの電析-Cu電析物への不純物の混入と溶融塩浴の精製-
小浦延幸，清木 賢，田邉尚敬，八代高士, 宇井幸一, 伊藤 滋
表面技術 ( 一般社団法人 表面技術協会 ) 56 ( 3 ) 151 - 157 2005年03月 [査読有り]
学術誌 共著・分担
High purity Cu electrodeposition from a CuCl-1-Butylpyridinium chloride (BPC) ambient-temperature molten salt electrolyte has been investigated. In this study, silver was examined as an impurity. Ag did not electrodeposit in the Cu deposit and the Cu purity was 99.9999%, if the Ag(I) ion concentration was controlled to be less than 10 ppm in the 66.7mol%CuCl-33.3mol%BPC melt and less than 12ppm in the 44.0mol%CuCl-56.0mol%BPC melt. In addition, a method removal of the Ag(I) ion from the melt was studied. The method of refining by galvanostatic electrolysis at a large current density (25mA·cm−2) was effective, and the Ag(I) ion concentration in the melt decreased to lower than 9ppm. Furthermore, the codeposit of Cu with the N included in the BPC, which was the main content in the bath was also examined. The electrodeposition of N was not recognized.
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電気めっき法で作製したAlめっき膜のリチウム二次電池用負極への応用
宇井幸一*, 南 拓人, 石川恒平, 井手本 康, 小浦延幸
Electrochemistry ( The Electrochemical Society of Japan ) 73 ( 4 ) 279 - 283 2005年04月 [査読有り]
学術誌 共著・分担
The Al film prepared by the electroplating method was applied to the negative electrode for lithium secondary batteries. The electroplated Al film obtained from a 66.7 mol% AlCl3-33.3 mol% EMIC ambient-temperature molten salt melt was used. The discharge potential of the electroplated Al negative electrode showed the flat potential profile at 0.4 V vs. Li+/Li. The discharge capacity of 2nd to 5th cycle was 224-400 mAh g-1 and the charge-discharge efficiency maintained ca. 90%. It was found that the electroplated Al electrode as the negative electrode for lithium secondary batteries operates quite effectively.
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Hidenori MATSUZAWA, Ryo NAKAI, Koichi UI, Nobuyuki KOURA*, and Guoping LING
Electrochemistry ( The Electrochemical Society of Japan ) 73 ( 8 ) 715 - 723 2005年08月 [査読有り]
学術誌 共著・分担
The structure of the ionic species in an SnCl2-1-ethyl-3-methylimidazolium chloride (EMIC) melt was examined using density functional theory (DFT) calculation and Raman spectroscopy. The Raman spectra of three different of SnCl2-EMIC melts, 33/67 (33 mol% SnCl2-67 mol% EMIC), 50/50, and 67/33 melts, were measured. The most stable structure of each SnCl2, SnCl3−, Sn2Cl4, Sn2Cl5−, EMI+, SnCl3− - EMI+ complex, or Sn2Cl5− - EMI+ complex was obtained using the B3LYP method with the LanL2DZ basis set. SnCl3− was found to be contained in all of the examined SnCl2-EMIC melts based on the assignment of the Raman spectra. Sn2Cl5− was contained in the acidic melts (SnCl2 > 50 mol%). The SnCl3− - EMI+ and Sn2Cl5− - EMI+ complexes as a microscopic structure in the SnCl2-EMIC melt were evaluated by a comparison between the harmonic frequencies and Raman spectra. In the SnCl3− - EMI+ complex, the SnCl3− was located on one side of EMI+ with a strong Coulombic force. Two possible structures of the Sn2Cl5− - EMI+ complex were obtained by a comparison between the calculated and experimental Raman spectra. Sn2Cl5− was also located on the same side of EMI+ as the SnCl3− - EMI+ complex.
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Lithium Battery Having a Large Capacity Using Fe3O4 as a Cathode Material
S. Ito*, K. Nakaoka, M. Kawamura, K. Ui, K. Fujimoto, and N. Koura
J. Power Sources ( Elsevier ) 146 ( 43832 ) 319 - 322 2005年08月 [査読有り]
学術誌 共著・分担
The lithium battery using Fe3O4 fine particles has been constructed. The discharge characteristics were improved by the addition of India ink or polyvinyl alcohol (PVA). The discharge potential at 60 °C maintained 2.5 V versus Li/Li+ up to 500 mAh g−1 and was 1.8 V at a large capacity of 926 mAh g−1. The possibility of secondary battery was discussed from the result of cycling test with 926 mAh g−1. Similar potential curve was obtained in the second cycle. Although degradation was observed in the third cycle, cyclability was maintained. However, the test cell stopped in fourth discharge. It is concluded that a large capacity was achieved at 60 °C using fine particles of Fe3O4 with PVA additive. According to the cycling test, it is expected to be a secondary battery by further development in nanostructure of the cathode.
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Koichi Ui*, Takuto Minami, Kohei Ishikawa, Yasushi Idemoto, Nobuyuki Koura
J. Power Sources ( Elsevier ) 146 ( 1-2 ) 698 - 702 2005年08月 [査読有り]
学術誌 共著・分担
performance of a binder-free carbon-negative electrode was investigated using the LiCl-saturated AlCl3–1-ethyl-3-methylimizadolium chloride (EMIC) + SOCl2 melt as the electrolyte for non-flammable lithium secondary batteries. Because the glass transition point of a LiCl-saturated 60.0 mol%AlCl3–40.0 mol%EMIC + 0.1 mol l−1 SOCl2 melt was −86.2 °C, the melt could be used as the electrolyte in a low-temperature domain. The binder-free carbon electrode made by the electrophoretic deposition method was used as the negative electrode. Four kinds of carbon materials, i.e., artificial graphite, natural graphite, soft carbon, and hard carbon were evaluated as the carbon electrode. For 30 cycles, the discharge capacities of these electrodes were 296–395 mAh g−1 and the charge–discharge efficiencies were more than 90%. The melt can be used as the electrolyte for non-flammable lithium secondary batteries and the binder-free carbon-negative electrode operates quite effectively.
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Corrosion behavior of Fe-Cr alloy in Li2CO3-K2CO3 Molten Carbonate
K. Takeuchi, A. Nishijima, K. Ui, N. Koura*, and Chun -K. Loon
J. Electrochem. Soc. ( Electrochemical Society ) 152 ( 9 ) B364 - B368 2005年09月 [査読有り]
学術誌 共著・分担
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Li二次電池正極活物質LixMn1-yMyO2(M=Mn,Al,Cu)の熱力学安定性および結晶構造に及ぼすLi組成比の影響
井手本 康*, 近野雄志, 宇井幸一, 小浦延幸
Electrochemistry 73 ( 9 ) 823 - 829 2005年09月 [査読有り]
学術誌 共著・分担
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Y. Idemoto*, T. Mochizuki, K. Ui , and N. Koura
J. Electrochem. Soc. ( Electrochemical Society ) 153 ( 2 ) A418 - A424 2006年02月 [査読有り]
学術誌 共著・分担
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Chun -K. Loong *, M. Ozawa, K. Takeuchi, K. Ui, and N. Koura
J. Alloys Compd. ( Elsevier ) 408-412 1065 - 1070 2006年02月 [査読有り]
学術誌 共著・分担
The techniques of neutron scattering were applied to characterize two rare-earth containing ceramic systems: oxide-based automotive three-way catalysts and proton-conducting cerate-perovskite-based hydrogen-separation membranes. High-surface-area zirconias are widely used as catalytic support of noble metals in automotive three-way catalytic converters for exhaust gas treatment. Doping these oxides with rare-earth elements provides an important means in tailoring their properties for better catalytic performance. We have carried out in situ small-to-wide angle neutron diffraction at high temperatures and under controlled atmospheres to study the sintering behavior and the Ce3+ ↔ Ce4+ redox process in CexZr1−xO2−δ solid solutions dispersed with Pt nanoparticles. We found substantial effects due to RE-doping on the nature of aggregation of nanoparticles, defect formation, crystal phase transformation, and metal-support interaction. Y-doped BaCeO3 exhibits significant proton conductivity under a hydrogen-containing atmosphere at high temperatures. This system has high potential for applications as fuel-cell electrolytes, gas sensors, and ceramic membranes for hydrogen separation. We have performed in situ neutron diffraction to obtain information regarding the crystal phase evolution that permits dissolution of hydrogen and proton migration through the lattice. Neutron quasielastic- and inelastic-scattering experiments were carried out to investigate the proton dynamics from local vibrations to long-range diffusion.
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T. Yatsushiro, N. Koura*, S. Nakano, K. Ui, and K. Takeuchi
Electrochemistry 74 ( 3 ) 233 - 236 2006年03月 [査読有り]
学術誌 共著・分担
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CuCl-1-ブチルピリジニウムクロリド系常温型溶融塩浴を用いたCu(Ⅰ)イオンからのCuの電析－有機溶媒混合浴
宇井幸一, 中矢清隆, 高橋康明, 田邊尚敬, 井手本 康, 小浦延幸
表面技術 57 ( 4 ) 300 - 301 2006年04月 [査読有り]
学術誌 共著・分担
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有機溶媒添加ZnCl2-NiCl2-EMIC常温型溶融塩浴を用いたクラックフリー非晶質Zn-Ni合金の電析
宇井幸一, 上浦尚子, 井手本 康, 小浦延幸, 山崎貴司
表面技術 57 ( 5 ) 383 - 384 2006年05月 [査読有り]
学術誌 共著・分担
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K. Ui, T. Fujita, N. Koura*, and F. Yamaguchi
J. Electrochem. Soc. ( Electrochemical Society ) 153 ( 6 ) C449 - C454 2006年06月 [査読有り]
学術誌 共著・分担
The application of TiO2 has been extensively studied, because the TiO2 produces a photocatalytic reaction that decomposes harmful materials using sunlight energy. In this study, the immobilization of the TiO2 particle on a brass substrate was examined using the composite coating method. As a result of evaluating the surface morphology using a scanning electron microscope, it was found that the co-deposited TiO2(anatase) (TiO2(A)) particles were exposed on the surface of the Ag or Cu-TiO2(A) particle composite coating films. The proportion of the TiO2(A) particle on the surface increased with increasing the co-deposit volume ratio of the TiO2(A) particle. The photocatalytic activity of the Ag-TiO2(A) composite film was significantly better than that of the Cu-TiO2(A) composite film. The cause for this difference was attributed to the effect of Ag itself (in the dark) and the synergistic effect of Ag and TiO2(A) (under UV irradiation).
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泳動電着法を用いたLi イオン二次電池用バインダーフリー正極の作製
宇井幸一*, 府野信也, 長瀬 浩, 井手本 康, 小浦延幸
Electrochemistry 74 ( 6 ) 474 - 478 2006年06月 [査読有り]
学術誌 共著・分担
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常温型溶融塩を電解液に用いるAl二次電池用正極活物質としてのポリパラフェニレンの応用
宇井幸一, 久間義文, 小浦延幸*
Electrochemistry 74 ( 7 ) 536 - 538 2006年07月 [査読有り]
学術誌 共著・分担
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Growth model of Reversed Taper during Early Stage of D.C. Etching on Aluminum Oriented to (100),
K. Ui, T. Yamazaki, N. Koura*, Y. Idemoto, T. Makino, M. Furukawa, and H. Uchi
Electrochemistry 74 ( 9 ) 737 - 743 2006年09月 [査読有り]
学術誌 共著・分担
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Cathode Performance of Lithium Non-stoichiometric Li[Lix(Ni1/3Co1/3Mn1/3)1-x]O2 Material for Li-ion Batteries
Jung-Min Kim, Naoaki Kumagai*, Yoshihiro Kadoma, Koichi Ui, and Hitoshi Yashiro
ITE Letters on Batteries, New Technologies & Medicine 7 ( 5 ) 454 - 457 2006年10月 [査読有り]
学術誌 共著・分担
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泳動電着法によるPb-Zr-Ti-Nb-Si-O系強誘電体厚膜の作製
井手本 康*, 吉田理志, 宇井幸一，小浦延幸
Electrochemistry 74 ( 11 ) 883 - 889 2006年11月 [査読有り]
学術誌 共著・分担
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森田秀利, 大畑秀明, 竹内 謙, 宇井幸一, 小沢幸三, 小浦延幸*
Electrochemistry 75 ( 6 ) 466 - 471 2007年06月 [査読有り]
学術誌 共著・分担
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Fabrication of Electrode for Capacitor Cell Prepared by Electrophoretic Deposition Method
Koichi Ui*, Kazuma Okura, Nobuyuki Koura, Satoru Tsumeda, and Kenji Tamamitsu
Electrochemistry 75 ( 8 ) 604 - 606 2007年08月 [査読有り]
学術誌 共著・分担
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Equilibrium Geometries and Structural Stability of the AlmNan (m=2-4; n=1-8) Clusters
Hidenori Matsuzawa*, Kazuhiro Sato, Takuji Hirata, Koichi Ui, and Nobuyuki Koura
J. Chem. Theory Comput. ( American Chemical Society ) 3 ( 5 ) 1818 - 1829 2007年09月 [査読有り]
学術誌 共著・分担
The stable geometries and formation processes of the AlmNan (m = 2-4; n = 1-8) clusters were investigated using the density functional theory (DFT). The Alm (m = 2-4) structures are maintained in the clusters. The Na atoms are attached to the Al-Al bond or Al plane for less than n = 4 in the AlmNan (m = 2-4) clusters. The odd electron of the attached Na atom is transferred to the Alm part for n 4 or 5 in the AlmNan (m = 2-4) clusters since the Alm part becomes stable. The Na-Na bonding is formed by the attached Na atom after saturation of the Al-Al bonds or Al atoms. The Al2Na5, Al3Na5, Al3Na6, Al3Na7, and Al3Na8 clusters have a characteristic structure. The Na wing is formed in the Al3Nan (n = 5-8) clusters. The 2S shell containing the 3s orbital of the Na atom and the 3p orbital of the Al atom becomes stable before the occupation of the 1D shell because the electrons are delocalized on the Na plane for n 5 in the AlmNan (m = 2-4) clusters. The stability of the AlmNan (m = 2-4; n = 1-8) clusters was evaluated by comparison of the vertical ionization potential (IP), HOMO-LUMO gap, adsorption energy of the Na atom, and binding energy per atom.
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Jung-Min Kim, Yoshihiro Kadoma, Koichi Ui, and Naoaki Kumagai*
ITE Letters on Batteries, New Technologies & Medicine 8 ( 5 ) B12 - B16 2007年10月 [査読有り]
学術誌 共著・分担
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ジメチルエーテルを直接燃料に用いた中温作動型SOFC用新規アノード触媒の開発
竹内 謙*, 石田洋介, 粕谷健太, 田井良典, 古屋仲秀樹, 宇井幸一, 小浦延幸
Electrochemistry 75 ( 10 ) 786 - 790 2007年10月 [査読有り]
学術誌 共著・分担
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Koichi Ui, Shinei Kikuchi; Fuminobu Mikami; Yoshihiro, Kadoma, and Naoaki Kumagai*
J. Power Sources 173 ( 1 ) 518 - 521 2007年11月 [査読有り]
学術誌 共著・分担
In order to improve the negative electrode characteristics of a graphite electrode in a propylene carbonate (PC)-containing electrolyte, we have prepared a graphite negative electrode coated with a water-soluble anionic polymer as a binder for composite graphite electrodes. The electrochemical characteristics of the coated graphite were evaluated by cyclic voltammetry and charge–discharge cycle tests. The coated graphite negative electrode showed a stable Li+ ion intercalation/deintercalation reaction without the exfoliation of the graphene layers caused by the co-intercalation of the PC solvent in the LiClO4/PC solution. The charge–discharge characteristic of the coated graphite negative electrode in a PC-containing electrolyte was almost the same as that in ethylene carbonate-based electrolyte.
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エチレングリコールを混合したZnCl2-NiCl2-EMIC常温型溶融塩浴を用いたクラックフリー非晶質Zn-Ni合金の電析
小浦延幸,上浦尚子,竹内 謙, 宇井幸一, 山崎貴司
表面技術 58 ( 11 ) 682 - 688 2007年11月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Satoru Oshitari, Koichi Ui, and Naoaki Kumagai*
Electrochim. Acta. 53 ( 4 ) 1697 - 1702 2007年12月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Naoaki Kumagai*, Satoru Oshitari, and Koichi Ui
ITE Letters on Batteries, New Technologies & Medicine 8 ( 6 ) 674 - 678 2007年12月 [査読有り]
学術誌 共著・分担
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Electroless Plating of Aluminum from a Room-Temperature Ionic Liquid Electrolyte
Nobuyuki Koura*, Hiroshi Nagase, Atsushi Sato, Shintaro Kumakura, Ken Takeuchi, Koichi Ui, Tetsuya Tsuda, and Chun K. Loong
J. Electrochem. Soc. 155 ( 2 ) D155- - D157 2008年02月 [査読有り]
学術誌 共著・分担
Because aluminum is a less-noble metal which has the standard electrode potential of −1.676 V vs normal hydrogen electrode, it is impossible to obtain the electrodeposition of aluminum from an aqueous solution. No one has reported an electroless plating method of aluminum. We succeeded in demonstrating the electroless plating of aluminum from a room-temperature ionic liquid (RTIL). It was found from measurements of inductively coupled plasma, X-ray diffraction, scanning electron microscopy (SEM), SEM-energy-dispersive X-ray analysis, and glow discharge optical emission spectroscopy that dense, smooth, and pure aluminum plating was obtained from the RTIL by the electroless plating method. Moreover, the reaction mechanism of the electroless plating of aluminum from the RTIL electrolyte was electrochemically analyzed.
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Structural Modification of Li[Li0.27Co0.20Mn0.53]O2 by Lithium Extraction and its Electrochemical Property as the Positive Electrode for Li-ion Batteries
Naoaki Kumagai*, Jung-Min Kim, Syo Tsuruta, Yoshihiro Kadoma, and Koichi Ui
Electrochim. Acta. 53 ( 16 ) 5287 - 5293 2008年06月 [査読有り]
学術誌 共著・分担
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Development of Non-flammable Lithium Secondary Battery with Room-temperature Ionic Liquid Electrolyte -Performance of Electroplated Al film negative electrode-
Koichi Ui*, Keigo Yamamoto, Kohei Ishikawa, T. Minami, Ken Takeuchi, Masayuki Itagaki, Kunihiro Watanabe, and Nobuyuki Koura
J. Power Sources 183 ( 1 ) 347 - 350 2008年08月 [査読有り]
学術誌 共著・分担
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A rechargeable lithium metal battery operating at intermediate temperatures using molten alkali bis(trifluoromethylsulfonyl)amide mixture as an electrolyte
Atsushi Watarai, Keigo Kubota, Masaki Yamagata, Takuya Goto, Toshiyuki Nohira, Rika Hagiwara, Koichi Ui, Naoaki Kumagai
J. Power Sources 183 724 - 729 2008年08月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Satoru Oshitari, Koichi Ui, and Naoaki Kumagai*
Solid State Ionics 179 1710 - 1713 2008年09月 [査読有り]
学術誌 共著・分担
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Ryosuke Tai, Koichi Ui, Ken Takeuchi*, Kenjiro Fujimoto, and Shigeru Ito
Electrochemistry 77 ( 2 ) 149 - 151 2009年02月 [査読有り]
学術誌 共著・分担
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ジメチルエーテルを直接燃料に用いた中温作動型SOFC用Fe触媒の開発
石田洋介, 田井良典, 宇井幸一, 竹内 謙*, 藤本憲次郎, 伊藤 滋
Electrochemistry 77 ( 3 ) 225 - 228 2009年03月 [査読有り]
学術誌 共著・分担
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Electrochemical Characteristics of Sn Film Prepared by Pulse Electrodeposition Method as Negative Electrode for Lithium Secondary Batteries
Koichi Ui*, Shinei Kikuchi, Yoshihiro Kadoma, Naoaki Kumagai, and Shigeru Ito
J. Power Sources 189 224 - 229 2009年04月 [査読有り]
学術誌 共著・分担
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Li+ Ion-exchanged Hollandite-type MnO2 in Molten Salt at Several Temperatures and Electrochemical Properties for Lithium Battery Electrodes
Yoshihiro KADOMA, Ryo KIMURA, Koichi UI, and Naoaki KUMAGAI *
Electrochemistry 77 ( 8 ) 751 - 753 2009年08月 [査読有り]
学術誌 共著・分担
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Electrodeposition of Nb3Sn Alloy Film from Lewis Basic NbCl5-SnCl2-EMIC Melt
Koichi Ui*, Hirokazu SAKAI, Ken TAKEUCHI, Guo-ping LING, and Nobuyuki KOURA
Electrochemistry 77 ( 9 ) 798 - 800 2009年09月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Jung-Min Kim, Katsutoshi Abiko, Keitaro Ohtsuki, Koichi Ui, and Naoaki Kumagai*
Electrochim. Acta. 55 ( 3 ) 1034 - 1041 2010年01月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Jung-Min Kim, Koichi Ui, Naoaki Kumagai*, Naoto Kitamura, and Yasushi Idemoto
Electrochim. Acta. 55 ( 6 ) 1872 - 1879 2010年02月 [査読有り]
学術誌 共著・分担
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Yoshihiro KADOMA, Seiyu SATO, Koichi UI, and Naoaki KUMAGAI*
Electrochemistry 78 ( 8 ) 658 - 661 2010年08月 [査読有り]
学術誌 共著・分担
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Naoaki KUMAGAI*, Daisuke YOSHIKAWA, Yoshihiro KADOMA, and Koichi UI
Electrochemistry 78 ( 9 ) 754 - 756 2010年09月 [査読有り]
学術誌 共著・分担
Li4+xTi4.95−xNb0.05O12−δ (x=0.11∼0.13) materials were synthesized by using a spray-drying method followed by heat treating at 600∼900°C in air. Chemical and structural studies of the final products were done by X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) etc. The optimum synthesis condition of the materials was examined in relation to the electrochemical characteristics including charge-discharge cycling tests. The charge-discharge cycling results of several the Nb-substituted samples indicated that the samples prepared at heat treatment temperature of 700°C for 12 h showed best cycling performance with the discharge capacity of 175∼140 mAh g−1 at the discharge rate of 0.5∼3C.
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Preparation and cycle performance of Sn-SnOx/C composite electrode for lithium-ion battery
Ren, H.-J., Liu, W., Liu, G.-C., Ui, K., and Kumagai, N.
Journal of Functional Materials 42 ( 1 ) 19 - 22 2011年02月 [査読有り]
国際的学術誌 共著・分担
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Influence of the binder types on the electrochemical characteristics of natural graphite electrode in room-temperature ionic liquid
Koichi Ui*, Jun Towada, Sho Agatsuma, Naoaki Kumagai, Keigo Yamamoto, Hiroshi Haruyama, Ken Takeuchi, and Nobuyuki Koura
J. Power Sources 196 ( 8 ) 3900 - 3905 2011年04月 [査読有り]
学術誌 共著・分担
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Preparation of Co-Sn alloy film as negative electrode for lithium secondary batteries by pulse electrodeposition method
Koichi Ui*, Shinei Kikuchi, Yasuhiro Jimba, and Naoaki Kumagai
J. Power Sources 196 ( 8 ) 3916 - 3920 2011年04月 [査読有り]
学術誌 共著・分担
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パルス電解法を用いるリチウムイオン二次電池用Ni-Sn合金めっき膜負極の作製
宇井幸一*, 瓦井 究, 佐藤吉信, 菊地信栄, 熊谷直昭
表面技術 ( 一般社団法人 表面技術協会 ) 63 ( 3 ) 188 - 190 2012年03月 [査読有り]
学術誌 共著・分担
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Yoshihiro Kadoma, Tatsuya Akahira, Tsubasa Fukuda, Koichi Ui, and Naoaki Kumagai
Functional Materials Letters 5 ( 1 ) 1250004X 2012年04月 [査読有り]
学術誌 共著・分担
Hollandite-type MnO2 and its Co-substituted samples have been synthesized by hydrothermal method from MnSO4, CoSO4 and K2S2O8 solutions. The hydrothermal products from MnSO4 and K2S2O8 solutions consisted of the hollandite-type [2 × 2] tunnel structure at 100°C–150°C for 12 h, which was transformed to pyrolusite-type [1 × 1] tunnel structure by hydrothermal treatment at 150°C for longer times of 24–48 h or at a higher temperature of 180°C. On the other hand, the hydrothermal products from MnSO4, CoSO4 and K2S2O8 solutions at 150°C–180°C for 12–48 h consisted of the hollandite-type MnO2 phase. The Co-substituted samples showed higher initial discharge capacity (180–200 mAh (g-oxide)-1) than that of non-substituted hollandite-type MnO2 (130–160 mAh (g-oxide)-1) at 50 mA g-1.
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Li excess Li4+xTi5-xO12-λ/C composite using spray-drying method and its electrode properties
Daisuke Yoshikawa, Norio Suzuki, Yoshihiro Kadoma, Koichi Ui, and Naoaki Kumagai
Functional Materials Letters 5 ( 1 ) 12500014 2012年04月 [査読有り]
学術誌 共著・分担
We have prepared a lithium excess carbon composite material, Li4+xTi5-xO12-δ/C (LTO/C), using various amounts of sucrose as a carbon source by the spray-drying method. The prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and elemental analysis. The prepared material had the Li4Ti5O12 phase including 3.9–18.4 wt.% carbon. Transmission electron microscopy images and the selected area diffraction (SAD) pattern showed that the prepared materials consisted of a carbon nanonetwork in the LTO/C composite. The charge–discharge cycling tests were carried out using the R2032 coin-type cell under the following conditions; 1.2–3.0 V, 0.1 C–10 C (1 C = 175 mA g-1), 25°C. Based on the electrochemical results, the electrode performance of the prepared material was improved with increasing amounts of residual carbon, in particular, LTO/C including 6.2 wt.% residual carbon exhibited the best electrode performance of 156 mAh g-1 at 1 C during 50 cyclings when compared to the other materials.
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Yoshihiro KADOMA, Yusuke CHIBA, Daisuke YOSHIKAWA, Yuko MITOBE, Naoaki KUMAGAI, and Koichi UI*
Electrochemistry ( 公益社団法人 電気化学会 ) 80 ( 10 ) 759 - 761 2012年10月 [査読有り]
学術誌 共著・分担
We have investigated the preparation and electrochemical characteristics of a lithium excess Li4.3Ti5O12 carbon composite (Li4.3Ti5O12/C) with different carbon sources (polyacryl acid, polyvinyl alcohol, and carboxy methyl cellulose sodium). We have prepared the lithium excess Li4.3Ti5O12/C by a spray-drying method followed by calcining at 800oC in a nitrogen atmosphere. The TEM observations indicated that the surface of the Li4.3Ti5O12/C particle was clearly covered with an amorphous carbon layer. The Li4.3Ti5O12/C materials employing polyvinyl alcohol as the carbon source showed the best rate performance with the highest discharge capacity of 117 mAh (g-Li4.3Ti5O12/C)-1 at the 10C rate.
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Fabrication of binder-free SnO2 nanoparticle electrode for lithium secondary batteries by electrophoretic deposition method
Koichi Ui*, Soshi Kawamura, and Naoaki Kumagai
Electrochim. Acta. 76 383 - 388 2012年08月 [査読有り]
学術誌 共著・分担
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Influence of the binder types on the electrochemical characteristics of tin nanoparticle negative electrode for lithium secondary batteries
Guichang Liu*, Xiaoxiao Shen, Koichi Ui, Lida Wang, and Naoaki Kumagai
J. Power Sources 217 108 - 113 2012年11月 [査読有り]
学術誌 共著・分担
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リチウムイオンを含む塩化アルミニウム系室温イオン液体中における天然黒鉛電極の電気化学反応の解析
十和田 潤, 門磨義浩, 嶋田和明, 熊谷直昭, 宇井幸一 *
Electrochemistry 81 ( 6 ) 432 - 439 2013年06月 [査読有り]
学術誌 共著・分担
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Analysis of SEI formation reaction and surface deposit of natural graphite negative electrode employing polyacrylic acid as a binder
Koichi Ui*, Daisuke Fujii, Yuki Niwata, Tomohiro Karouji, Yu Shibata, Yoshihiro Kadoma, Kazuaki Shimada, and Naoaki Kumagai
J. Power Sources 247 981 - 990 2014年02月 [査読有り]
学術誌 共著・分担
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ソルボサーマル法によるLiMnPO4の合成とその炭素複合体の電気化学的特性
門磨義浩,* 原田晃一, 渡辺 久, 熊谷直昭, 宇井幸一
Electrochemistry 82 ( 6 ) 456 - 461 2014年06月 [査読有り]
学術誌 共著・分担
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パルス電解法で作製したリチウム二次電池用Ni-Sn合金めっき膜負極の組成が充放電特性に及ぼす影響
宇井幸一*, 瓦井 究, 門磨義浩, 熊谷直昭
表面技術 ( 一般社団法人 表面技術協会 ) 64 ( 8 ) 460 - 466 2013年08月 [査読有り]
学術誌 共著・分担
Using pulse electrolysis, Ni-Sn alloy films of three compositions (NiSn9, Ni2Sn8, and Ni3Sn7) were prepared for a negative electrode. FESEM observations indicated that the crystal grain size of the film decreased, and that the film was densified with increased Ni contents. Tape tests indicated that adhesion between the film and a current collector increased concomitantly with increased Ni content. The galvanostatic charge-discharge tests indicated that the capacity retention rate at the 30th cycle rose with increased Ni content. Ex-situ FE-SEM observations indicated that cracks in the film were generated in the Ni2Sn8 and Ni3Sn7 alloy films after the first discharge. Ex-situ XRD measurements showed that the charge-discharge reaction of the Ni3Sn7 alloy film was attributable to alloying/dealloying a Ni3Sn4 phase with lithium. No β-Sn phase was extricated after the first discharging. In addition to the decrease in the crystal grain size and the increase in the adhesion between the film and the current collector along with increase in the Ni content, results showed that cycle performance can be improved if extrication of the β-Sn phase can be repressed, even if a crack is generated in the film during charging and discharging.
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Charge-discharge Characteristics of Natural Graphite Electrode in N, N-Diethyl- N-Methyl-N-(2-methoxyethyl)ammonium Bis(trifluoromethylsulfonyl)amide Containing Lithium Ion for Lithium-ion Secondary Batteries
Jun Towada, Tomohiro Karouji, Hiroki Sato, Yoshihiro Kadoma, Kazuaki Shimada, Koichi Ui*
J. Power Sources 275 50 - 54 2015年02月 [査読有り]
学術誌 共著・分担
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In situ SEM observation of the Si negative electrode reaction in an ionic-liquid-based lithium-ion secondary battery
Tetsuya Tsuda*, Tsukasa Kanetsuku, Teruki Sano, Yoshifumi Oshima, Koichi Ui, Masaki Yamagata, Masashi Ishikawa, Susumu Kuwabata
Microscopy 64 ( 3 ) 1 - 10 2015年06月 [査読有り]
国際的学術誌 共著・分担
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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.