Published Papers - UI Koichi

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