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

Crystal Structural Change during Charge-Discharge Process of LiMn_1.5Ni_0.5O₄ as Cathode Material for 5V Class Lithium Secondary Battery

Yasushi Idemoto *, Hiroshi Sekine, Koichi Ui, Nobuyuki Koura

Solid State Ionics ( Elsevier )  176 ( 3-4 ) 299 - 306   2005.01  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Pb Content and Oxygen Content Dependences of Tc and Jc for Bi_2.20-zPb_zSr_1.86Ca_2.03Y_0.05Cu_2.86O_y Superconducting Oxide

Y. Idemoto*, Y. Tsunochi, T. Miyabe, K. Ui, and N. Koura

Journal of the Ceramic Society of Japan ( The Chemical Society of Japan (CSJ) )  113 ( 2 ) 166 - 171   2005.02  [Refereed]

Academic Journal  Multiple authorship

DOI

Positive Electrode Performance of Nonflammable Lithium Secondary Battery with Ambient Temperature Molten Salt Electrolyte

Koichi UI*, Kohei ISHIKAWA, Takao FURUYA, Yasushi IDEMOTO, and Nobuyuki KOURA

Electrochemistry ( The Electrochemical Society of Japan )  73 ( 2 ) 120 - 122   2005.02  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Corrosion Behavior of Pb Alloys as Negative Current Collector for Lead Acid Batteries in Charged State

Nobuyuki KOURA*, Kenta KASUYA, Koichi UI, Yuki TAKIGUCHI, and Yasushi IDEMOTO

Electrochemistry ( The Electrochemical Society of Japan )  73 ( 2 ) 135 - 140   2005.02  [Refereed]

Academic Journal  Multiple authorship

DOI

High Purity Cu Deposition from Cu(I) Ion in CuCl-1-1Butylpyridinium Chloride Ambient-Temperature Molten Salts -Impurity in the Cu Deposit and Purification of the Melts-

Nobuyuki KOURA, Satoshi SEIKI, Naotaka TANABE, Takashi YATSUSHIRO, Koichi UI, and Shigeru ITO

Journal of The Surface Finishing Society of Japan ( The Surface Finishing Society of Japan )  56 ( 3 ) 151 - 157   2005.03  [Refereed]

Academic Journal  Multiple authorship

DOI

Application to Negative Electrode for Lithium Secondary Batteries of Electroplated Aluminum Electrode

Koichi UI*, Takuto MINAMI, Kohei ISHIKAWA, Yasushi IDEMOTO, and Nobuyuki KOURA

Electrochemistry ( The Electrochemical Society of Japan )  73 ( 4 ) 279 - 283   2005.04  [Refereed]

Academic Journal  Multiple authorship

DOI

Structure of SnCl₂-1-ethyl-3-methylimidazolium Chloride Ambient-Temperature Molten Salt using Density Functional Theory Calculation and Raman Spectroscopy

Hidenori MATSUZAWA, Ryo NAKAI, Koichi UI, Nobuyuki KOURA*, and Guoping LING

Electrochemistry ( The Electrochemical Society of Japan )  73 ( 8 ) 715 - 723   2005.08  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

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   2005.08  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Development of Nonflammable Lithium Secondary Battery with Ambient-Temperature Molten Salt Electrolyte : Performance of binder-free carbon-negative electrode

Koichi Ui*, Takuto Minami, Kohei Ishikawa, Yasushi Idemoto, Nobuyuki Koura

J. Power Sources ( Elsevier )  146 ( 1-2 ) 698 - 702   2005.08  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

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   2005.09  [Refereed]

Academic Journal  Multiple authorship

DOI

Li Content Dependence of Thermodynamic Stability and the Crystal Structure of Li_xMn_1-yM_yO₂(M=Mn,Al,Cu) as a Cathode Active Material for Li Secondary Battery

Yasushi Idemoto*, Yuji Konno, Koichi UI, and Nobuyuki Koura

Electrochemistry   73 ( 9 ) 823 - 829   2005.09  [Refereed]

Academic Journal  Multiple authorship

Properties, Crystal Structure and Performance of o-LiMnO₂ as Cathode Material for Li Secondary Batteries

Y. Idemoto*, T. Mochizuki, K. Ui , and N. Koura

J. Electrochem. Soc. ( Electrochemical Society )  153 ( 2 ) A418 - A424   2006.02  [Refereed]

Academic Journal  Multiple authorship

DOI

Neutron Studies of Rare Earth-Modified Zirconia Catalyst and Yttrium-Doped Barium Cerate Proton-Conducting Ceramic Membranes

Chun -K. Loong *, M. Ozawa, K. Takeuchi, K. Ui, and N. Koura

J. Alloys Compd. ( Elsevier )  408-412   1065 - 1070   2006.02  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Electrodeposition of Aluminum-Carbon Nanotube Composite from Room-Temperature Molten Salt Electrolyte

T. Yatsushiro, N. Koura*, S. Nakano, K. Ui, and K. Takeuchi

Electrochemistry   74 ( 3 ) 233 - 236   2006.03  [Refereed]

Academic Journal  Multiple authorship

Cu Deposition from Cuprous Ion in CuCl-1-Butylpyridinium Chloride Ambient-Temperature Molten Salt -Organic Solvent Mixed Bath

Koichi UI, Kiyotaka NAKAYA, Yasuaki TAKAHASHI, Naotaka TANABE, Yasushi IDEMOTO, and Nobuyuki KOURA

Journal of The Surface Finishing Society of Japan   57 ( 4 ) 300 - 301   2006.04  [Refereed]

Academic Journal  Multiple authorship

Electrodeposition of Crack-Free Amorphous Zn-Ni Alloy from Organic Solvent Added ZnCl₂-NiCl₂-EMIC Ambient-Temperature Molten Salt Bath

Koichi UI*, Naoko KAMIURA, Yasushi IDEMOTO, Nobuyuki KOURA and Takashi YAMAZAKI

Journal of The Surface Finishing Society of Japan   57 ( 5 ) 383 - 384   2006.05  [Refereed]

Academic Journal  Multiple authorship

Preparation of Ag-TiO₂(anatase) particle composite coating film and its photocatalytic reaction mechanism

K. Ui, T. Fujita, N. Koura*, and F. Yamaguchi

J. Electrochem. Soc. ( Electrochemical Society )  153 ( 6 ) C449 - C454   2006.06  [Refereed]

Academic Journal  Multiple authorship

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).

DOI

Fabrication of Binder-Free Positive Electrode for Li-ion Secondary Batteries by Electrophoretic Deposition Method

K. Ui*, S. Funo, H. Nagase, Y. Idemoto, and N. Koura

Electrochemistry   74 ( 6 ) 474 - 478   2006.06  [Refereed]

Academic Journal  Multiple authorship

Application of poly-p-phenylene as Positive Electrode Active Material for Al Secondary Battery with Ambient-Temperature Molten Salt Electrolyte

K. Ui, Y. Kuma, and N. Koura

Electrochemistry   74 ( 7 ) 536 - 538   2006.07  [Refereed]

Academic Journal  Multiple authorship

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   2006.09  [Refereed]

Academic Journal  Multiple authorship

Cathode Performance of Lithium Non-stoichiometric Li[Li_x(Ni_1/3Co_1/3Mn_1/3)_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   2006.10  [Refereed]

Academic Journal  Multiple authorship

Preparation of Pb-Zr-Ti-Nb-Si-O Ferroelectric Thick Film by Electrophoretic Deposition

Yasushi Idemoto*, Satoshi Yoshida, Koichi Ui, and Nobuyuki Koura

Electrochemistry   74 ( 11 ) 883 - 889   2006.11  [Refereed]

Academic Journal  Multiple authorship

A Local Structure Analysis of Molten Li₂CO₃ Using the Density Functional Theory

Hidetoshi Morita, Hideaki Ohata, Ken Takeuchi, Koichi Ui, Kozo Kozawa, and Nobuyuki Koura*

Electrochemistry   75 ( 6 ) 466 - 471   2007.06  [Refereed]

Academic Journal  Multiple authorship

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   2007.08  [Refereed]

Academic Journal  Multiple authorship

Equilibrium Geometries and Structural Stability of the Al_mNa_n (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   2007.09  [Refereed]

Academic Journal  Multiple authorship

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.


DOI

Electrochemical Properties of Li_1+x(Ni_0.4Co_0.2Mn_0.4)_1-xO₂ (x = 0.00 and 0.05) for Lithium-ion Batteries

Jung-Min Kim, Yoshihiro Kadoma, Koichi Ui, and Naoaki Kumagai*

ITE Letters on Batteries, New Technologies & Medicine   8 ( 5 ) B12 - B16   2007.10  [Refereed]

Academic Journal  Multiple authorship

Development of novel anodic catalyst for solid oxide fuel cell operated at intermediate-temperature direct utilizing of dimethylether fuel

Ken Takeuchi*, Yousuke Ishida, Kenta Kasuya, Ryosuke Tai, Hideki Koyanaka, Koichi Ui, and Nobuyuki Koura

Electrochemistry   75 ( 10 ) 786 - 790   2007.10  [Refereed]

Academic Journal  Multiple authorship

Improvement of Electrochemical Characteristics of Natural Graphite Negative Electrode Coated with Polyacrylic Acid in Pure Propylene Carbonate Electrolyte

Koichi Ui, Shinei Kikuchi; Fuminobu Mikami; Yoshihiro, Kadoma, and Naoaki Kumagai*

J. Power Sources   173 ( 1 ) 518 - 521   2007.11  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Electrodeposition of Crack-Free Amorphous Zn-Ni Alloy from Ethylene Glycol Mixed ZnCl₂-NiCl₂-EMIC Ambient-Temperature Molten Salt Bath

Nobuyuki KOURA*, Naoko KAMIURA, Ken TAKEUCHI, Koichi UI, and Takashi YAMAZAKI

Journal of The Surface Finishing Society of Japan   58 ( 11 ) 682 - 688   2007.11  [Refereed]

Academic Journal  Multiple authorship

Synthesis of Hollandite-type Li_xMnO₂ by Li⁺ ion-exchange in molten salt and lithium insertion characteristics

Yoshihiro Kadoma, Satoru Oshitari, Koichi Ui, and Naoaki Kumagai*

Electrochim. Acta.   53 ( 4 ) 1697 - 1702   2007.12  [Refereed]

Academic Journal  Multiple authorship

Structural and Electrochemical Properties of Li⁺ Ion-exchanged Hollandite-type MnO₂ for Lithium-ion Batteries

Yoshihiro Kadoma, Naoaki Kumagai*, Satoru Oshitari, and Koichi Ui

ITE Letters on Batteries, New Technologies & Medicine   8 ( 6 ) 674 - 678   2007.12  [Refereed]

Academic Journal  Multiple authorship

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   2008.02  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Structural Modification of Li[Li_0.27Co_0.20Mn_0.53]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   2008.06  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2008.08  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2008.08  [Refereed]

Academic Journal  Multiple authorship

Characterization and electrochemical properties of Li⁺ ion-exchanged products of hollandite-type K_y(Mn_1-xCo_x)O₂ for rechargeable lithium battery electrodes

Yoshihiro Kadoma, Satoru Oshitari, Koichi Ui, and Naoaki Kumagai*

Solid State Ionics   179   1710 - 1713   2008.09  [Refereed]

Academic Journal  Multiple authorship

Development of the Fe-Ni Anodic Catalyst for Solid Oxide Fuel Cell Operated at　Intermediate- temperature Direct Utilizing of Dimethylether Fuel

Ryosuke Tai, Koichi Ui, Ken Takeuchi*, Kenjiro Fujimoto, and Shigeru Ito

Electrochemistry   77 ( 2 ) 149 - 151   2009.02  [Refereed]

Academic Journal  Multiple authorship

Development of the Fe Anodic Catalyst for Solid Oxide Fuel Cell Operated at Intermediate-temperature Direct Utilizing of Dimethylether Fuel

Yousuke ISHIDA, Ryosuke TAI, Koichi UI, Ken TAKEUCHI, Kenjiro FUJIMOTO, and Shigeru ITO

Electrochemistry   77 ( 3 ) 225 - 228   2009.03  [Refereed]

Academic Journal  Multiple authorship

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   2009.04  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2009.08  [Refereed]

Academic Journal  Multiple authorship

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   2009.09  [Refereed]

Academic Journal  Multiple authorship

Optimization of electrochemical properties of LiFePO₄/C prepared by an aqueous solution method using sucrose

Yoshihiro Kadoma, Jung-Min Kim, Katsutoshi Abiko, Keitaro Ohtsuki, Koichi Ui, and Naoaki Kumagai*

Electrochim. Acta.   55 ( 3 ) 1034 - 1041   2010.01  [Refereed]

Academic Journal  Multiple authorship

Spray-drying Synthesized Lithium-excess Li_4+xTi_5−xO_12−δ and its Electrochemical Property as Negative Electrode Material for Li-ion Batteries

Yoshihiro Kadoma, Jung-Min Kim, Koichi Ui, Naoaki Kumagai*, Naoto Kitamura, and Yasushi Idemoto

Electrochim. Acta.   55 ( 6 ) 1872 - 1879   2010.02  [Refereed]

Academic Journal  Multiple authorship

Synthesis and Electrochemical Properties of LiNi_0.5-xMn_1.5-xM_2xO₄ (M ＝Al, Cr) Cathode Materials Prepared by PVA Method

Yoshihiro KADOMA, Seiyu SATO, Koichi UI, and Naoaki KUMAGAI*

Electrochemistry   78 ( 8 ) 658 - 661   2010.08  [Refereed]

Academic Journal  Multiple authorship

Spray-Drying Synthesized Lithium-excess Li_4+xTi_4.95-xNb_0.05O_12-δ and its Electrochemical Property as Negative Electrode Material for Li-ion Batteries

Naoaki KUMAGAI*, Daisuke YOSHIKAWA, Yoshihiro KADOMA, and Koichi UI

Electrochemistry   78 ( 9 ) 754 - 756   2010.09  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Preparation and cycle performance of Sn-SnO_x/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   2011.02  [Refereed]

Bulletin of University, Institute, etc.  Multiple authorship

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   2011.04  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2011.04  [Refereed]

Academic Journal  Multiple authorship

DOI

Preparation of Ni-Sn alloy film as negative electrode for lithium secondary batteries by pulse electrolysis

Koichi UI*, Kiwamu KAWARAI, Yoshinobu SATO, Shinei Kikuchi, Naoaki KUMAGAI

Journal of The Surface Finishing Society of Japan ( The Surface Finishing Society of Japan )  63 ( 3 ) 188 - 190   2012.03  [Refereed]

Academic Journal  Multiple authorship

DOI

Synthesis and electrochemical properties of nano fiber hollandite-type manganese oxides using a hydrothermal method

Yoshihiro Kadoma, Tatsuya Akahira, Tsubasa Fukuda, Koichi Ui, and Naoaki Kumagai

Functional Materials Letters   5 ( 1 ) 1250004X   2012.04  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Li excess Li_4+xTi_5-xO1_2-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   2012.04  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Influence of the Carbon Source on the Surface and Electrochemical Characteristics of Lithium Excess Li_4.3Ti₅O₁₂ Carbon Composite

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   2012.10  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

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   2012.08  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2012.11  [Refereed]

Academic Journal  Multiple authorship

DOI

Analysis of Electrochemical Reactions of Natural Graphite Electrode in Chloroaluminate Type Room-temperature Ionic Liquid Electrolyte Containing Lithium Ion

Jun TOWADA, Yoshihiro KADOMA, Kazuaki SHIMADA, Naoaki KUMAGAI, and Koichi UI *

Electrochemistry   81 ( 6 ) 432 - 439   2013.06  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2014.02  [Refereed]

Academic Journal  Multiple authorship

DOI

Solvothermal Synthesis and Electrochemical Properties of LiMnPO₄ and Its Carbon Composite

Yoshihiro KADOMA,* Koichi HARATA, Hisashi WATANABE, Naoaki KUMAGAI, and Koichi UI

Electrochemistry   82 ( 6 ) 456 - 461   2014.06  [Refereed]

Academic Journal  Multiple authorship

DOI

Influence on charge-discharge characteristics of composition of Ni-Sn alloy film negative electrode for lithium secondary batteries prepared by pulse electrolysis

Koichi UI*, Kiwamu KAWARAI, Yoshihiro KADOMA, Naoaki KUMAGAI

Journal of The Surface Finishing Society of Japan   64 ( 8 ) 460 - 466   2013.08  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2015.02  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2015.06  [Refereed]

Bulletin of University, Institute, etc.  Multiple authorship

DOI

Possibility of hot-dipped aluminum-coated steel sheet as current collector for lithium-ion secondary batteries

Setsuko KOURA, Takao TSUJIMURA, Satoru SASAKI, Takahiro ABE, Yuya TADA, Yoshinori KUDO, Ryohei SAITOU, Michimasa UCHIDATE, Yoshihiro KADOMA, and Koichi UI*

Journal of The Surface Finishing Society of Japan   67 ( 6 ) 316 - 321   2016.06  [Refereed]

Academic Journal  Multiple authorship

DOI

In situ Scanning Electron Microscopy of Silicon Anode Reactions in Lithium-Ion Batteries during Charge/Discharge Processes

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   2016.10  [Refereed]

Bulletin of University, Institute, etc.  Multiple authorship

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.

DOI J-GLOBAL

XAFS Analysis of Voltage Depression Mechanism after Charge-Discharge Cycling Tests for Li-rich Cathode Materials

Yuki Takei, Takahiro Endo, Akari Matsutomo, Hisashi Watanabe, Yoshihiro Kadoma, and Koichi Ui

SPring-8/SACLA Research Report   6 ( 2 ) 270 - 276   2018.08  [Refereed]

Academic Journal  Multiple authorship

DOI

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   2019.02  [Refereed]

International Conference Proceedings  Multiple authorship

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

DOI

Enhanced superconducting properties of double-chain based superconductor Pr2Ba4Cu7O15- δ synthesized by citrate pyrolysis technique

Kazuma Honnami, Michiaki Matsukawa*, Tatsuya Senzaki, Tomoki Toyama, Haruka Taniguchi, Koichi Ui, Takahiko Sasaki, Kohki Takahashi, Makoto Hagiwara

Physica C: Superconductivity and its Applications     2021.04  [Refereed]

International Conference Proceedings  Multiple authorship

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

DOI

Influence of Operating Conditions on Deposition Rate and Smoothness of Electrolytic Aluminum Foil Using Chloroaluminate Ionic Liquids

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   2021.05  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Synthesis of catalysts with fine platinum particles supported by high-surface-area activated carbons and optimization of their catalytic activities for polymer electrolyte fuel cells

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   2021.06  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Influence of Operating Conditions on Deposition Rate and Smoothness of Electrolytic Aluminum Foil Using Chloroaluminate Ionic Liquids

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   2024.03  [Refereed]

Others  Multiple authorship

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.

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   2024.04  [Refereed]

Academic Journal  Multiple authorship

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.

DOI

Effect of Operating Temperature and Additives to Chloroaluminate Ionic Liquid Electrolyte on Current Efficiency and Surface Morphology of Al Electrodeposit

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   2024.08  [Refereed]

Academic Journal  Multiple authorship

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.

DOI