Published Papers - UI Koichi

Studies on Components of Aluminium Negative Electrode for the Secondary Batteries with Room Temperature Molten Salt Electrolyte

Nobuyuki Koura*, Hidenori Tsuda, Koichi Ui

Denki Kagaku (presently Electrochemistry)   64 ( 11 ) 1195 - 1199   1996.11  [Refereed]

Academic Journal  Multiple authorship

DOI

Positive Electrode Active Material for the Rocking Chair Type Lithium Secondary Battery with an Ambient Temperature Molten Salt as a Nonflammable Electrolyte

Koichi UI, Nobuyuki KOURA, Yasushi IDEMOTO*, and Kazutaka IIZUKA

Denki Kagaku (presently Electrochemistry)   65 ( 2 ) 161 - 162   1997.02  [Refereed]

Academic Journal  Multiple authorship

1.381　2020 Journal Impact Factor (JIF)

DOI

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   1997.05  [Refereed]

Others  Multiple authorship

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.

DOI

Li-Al Negative Electrode Characteristics for the Rocking Chair Type Lithium Secondary Battery with a nonflammable Ambient Temperature Molten Salt Electrolyte

Nobuyuki Koura, Koichi Ui

Journal of Japan Institute of Light Metals   47 ( 5 ) 267 - 272   1997.05  [Refereed]

Academic Journal  Multiple authorship

DOI

V₂O₅ Positive Electrode Characteristics for the Rocking Chair Type Lithium Secondary Battery with a nonflammable Ambient Temperature Molten Salt Electrolyte

Nobuyuki Koura, Koichi Ui, Kazuyuki Takeishi

Journal of Japan Institute of Light Metals   47 ( 5 ) 273 - 278   1997.05  [Refereed]

Academic Journal  Multiple authorship

DOI

Discharge-Charge Characteristic of K -β-ferrite as Electrode Active Material for Lithium Secondary Battery

S. Ito, K. Ui, M. Ito, N. Koura, and K. Akashi

Journal of the Magnetics Society of Japan   22 ( 5 ) 449 - 451   1998.05  [Refereed]

Academic Journal  Multiple authorship

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   1998.11  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Li and Li-Al Negative Electrode Characteristics for the Lithium Secondary Battery with a Nonflammable SOCl₂, Li Added, LiCl Saturated AlCl₃-EMIC Molten Salt Electrolyte

Nobuyuki KOURA, Kazutaka IIZUKA, Yasushi IDEMOTO, Koichi UI

Electrochemistry ( The Electrochemical Society of Japan )  67 ( 6 ) 706 - 712   1999.06  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Preparation of Binder-Free Carbon Film by Electrophoretic Deposition Method

N. Koura, H. Tsuiki, N. Terakura, Y. Idemoto, F. Matsumoto, K. Ui, K. Yamada, and T. Mitate

Journal of The Surface Finishing Society of Japan   52 ( 1 ) 143 - 144   2001.01  [Refereed]

Academic Journal  Multiple authorship

DOI

Fabrication of Carbon Anode for Li-ion Secondary Batteries Prepared by Electrophoretic Deposition Method

N. Koura, S. Funo, H. Tsuki, Y. Idemoto, K. UI, F. Matsumoto

Journal of The Surface Finishing Society of Japan   53 ( 10 ) 683 - 687   2002.10  [Refereed]

Academic Journal  Multiple authorship

DOI

Dependence of Tc and Jc on Y Content and Oxygen Content for Bi_1.76Pb_0.44Sr_1.86Ca_2.08-xY_xCu_2.86O_y Superconducting Oxide

Y. Idemoto, Y. Tsunochi, K. Ui, and N. Koura

Journal of the Ceramic Society of Japan   111 ( 10 ) 781 - 785   2003.10  [Refereed]

Academic Journal  Multiple authorship

DOI

Dependence of Li content on Crystal Structure during the Charge-Discharge Process of LiMn_1.5Ni_0.5O₄ as a Cathode Materials for 5V Class Lithium Secondary Battery

Yasushi IDEMOTO*, Hiroshi SEKINE, Koichi UI, and Nobuyuki KOURA

Electrochemistry ( The Electrochemical Society of Japan )  71 ( 12 ) 1142 - 1144   2003.12  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Electronic States of Li_yMn_2-xM_xO₄ (M=Mn, Mg, Ni, Co) as a cathode Active Material for Li Secondary Battery by First-Principles Calculation using DV-Xα Method

Yuka ITO, Yasushi IDEMOTO*, Koichi UI, Nobuyuki KOURA

Electrochemistry ( The Electrochemical Society of Japan )  71 ( 12 ) 1145 - 1147   2003.12  [Refereed]

Academic Journal  Multiple authorship

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).

DOI

Enhancement of electrochemical oxidation of glucose at Hg adatom-modified Au electrode in alkaline aqueous solution

Futoshi MATSUMOTO*, Masahiro HARADA, Nobuyuki KOURA, Yasushi IDEMOTO, Koichi UI

Electrochemistry ( The Electrochemical Society of Japan )  72 ( 2 ) 103 - 110   2004.02  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

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   2004.03  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Oriented Electrodeposition of Aluminum from the Aluminum Chloride-1-Ethyl-3-Methylimidazolium Chloride Ambient Temperature Molten Salt -Effects of Xylene Mixing to the Orientation of Al Deposit-

Koichi UI, Takashi YATSUSHIRO, Masaki FUTAMURA, Yasushi IDEMOTO, Nobuyuki KOURA

Journal of The Surface Finishing Society of Japan ( The Surface Finishing Society of Japan )  55 ( 6 ) 409 - 416   2004.06  [Refereed]

Academic Journal  Multiple authorship

DOI

5V級Li二次電池用正極活物質LiMn_1.5Ni_0.5O₄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   2004.08  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Li二次電池正極材料Li_xMn_2-yM_yO₄(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   2004.10  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

化学的に脱LiしたLi二次電池正極活物質Li_xMn_2-yM_yO₄(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   2004.11  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Effect of Ferroelectric Properties on Heat Treatment for Bi_4-x+yLa_xTi₃O_12-d(x=0.5, y=0; x=0.75, y=0;x=0.75, y=0.15) Ferroelectric Ceramics

Yasushi IDEMOTO*, Naoto YOKOYAMA, Nobuyuki KOURA, Koichi UI

Journal of the Ceramic Society of Japan ( The Chemical Society of Japan (CSJ) )  112 ( 12 ) 669 - 673   2004.12  [Refereed]

Academic Journal  Multiple authorship

DOI