| INABA MINORU |  |
| Faculty of Science and Engineering Department of Molecular Chemistry and Biochemistry | |
| Professor |
Last Updated :2019/09/19
Researcher Profile and Settings
Profile and Settings
Profile
Professor Minoru Inaba received his B. Sc. from Faculty of Engineering, Kyoto University in 1984, and his M. Sc. in 1986 and Dr. Eng. in 1995 from Graduate School of Engineering, Kyoto University. He has worked on electrochemical energy conversion systems at Kyoto University (1992-2002) and at Doshisha University (2002-present). He has worked as the leader of a NEDO PEFC research project on platinum catalysts in FY2008-2019, and served as the chairperson of The Committee of Battery Technology, The Electrochemical Society of Japan (2015-18). His research interests are fundamental aspects in polymer electrolyte fuel cells, solid oxide fuel cells, and lithium-ion batteries. He has authored over 200 peer-reviewed papers, 60 review articles, 25 book chapters, and 20 patents.
Research Interests
Research Areas
Research History
- 1984-1994 Electrolysis using solid polymer electrolyte/electrode composites
- 1986-1992 Development of electroceremics
- 1992- In situ observation of the reactions at electrode/electrolyte interfaces in rechargeable lithium batteries
- 1992- Studies on oxygen reduction reaction in polymer electrolyte fuel cells
- 1993- Studies on low-temperature solid oxide fuel cells
- 2001-2007 Durability of polymer electrolyte fuel cells
- 2002- Electrode Materials for Next-Generation Lithium Ion Batteries
- 2008- Development of Highly Active and Durable Platinum Core-Shell Catalysts
Academic & Professional Experience
- Professor, Graduate School of Science and Engineering, Doshisha University, 2012/04 - Today
- Professor, Graduate School of Engineering, Doshisha University, 2010/04 - 2012/03
- Researcher, Tokuyama Corp., 1986 - 1992
- Instructor, Faculty of Engineering, Kyoto University, 1992 - 1996
- Instructor, Graduate School of Engineering, Kyoto University, 1996 - 1998
- Visiting Researcher, Lawrence Berkeley National Laboratory, USA, 1997 - 1998
- Associate Professor, Graduate School of Engineering, Kyoto University, 1998 - 2002
- Associate Professor, Faculty of Engineering, Doshisha University, 2002 - 2004
- Professor, Faculty of Engineering, Doshisha University, 2005 - 2008
- - Professor, Graduate School of Engineering, Doshisha Unviersity, 2007
- - Professor, Faculty of Science and Engineering, 2009
Education
- Kyoto University, Graduate School, Division of Engineering, 1986
- Kyoto University, Faculty of Engineering, 1984
Academic Degrees
Association Memberships
- Solid State Ionics Society of Japan
- International Sociery of Electrochemistry
- The Chemical Sociery of Japan
- The Carbon Society of Japan
- The Electrochemical Society
- The Electrochemical Society of Japan
- The Committee of Battery Technology
Committee Memberships
- Chairperson, 2016 -2018, The Committee of Battery Technology, Japan, Society
- Council board, 2004 -2005, The Electrochemical Society of Japan, Society, The Electrochemical Society of Japan
- Co-chairperson, 2011 -2015, The Committee of Battery Technology, Japan, Society, The Committee of Battery Technology
Awards & Honors
- The Committee of Bettery Technology Award
2001, japan - Best Paper Award, The Electrochemical Society, Japan
2008, japan - Most Cited Articles Award 2005-2009, Electrochimica Acta
2010 - Scientific Award, The Electrochemical Society, Japan
2011, japan
Published Papers
- Enhancement of anode activity and stability by Cr addition at Ni/Sm-doped CeO
2 cermet anodes in NH3 -fueled solid oxide fuel cells
Michihiro Hashinokuchi, Mengjia Zhang, Takayuki Doi, Minoru Inaba
© 2018 Chromium was added to nickel/Sm2O3-doped ceria (Ni/SDC) cermets by a CrCl3impregnation method, and the activity of the resulting Ni-Cr/SDC cermets was evaluated as anodes in ammonia-fueled solid oxide fuel cells (SOFCs) in the temperature range of 773 to 1173 K. It has been revealed that the addition of Cr was effective for the catalytic activity for NH3reforming, followed by hydrogen oxidation. The optimum amount of Cr was 3 at.% of the total metal in the Ni-Cr/SDC cermets. In addition, we demonstrated the improved stability of the Ni97-Cr3/SDC cermets in NH3atmosphere at 873 K. The addition of Cr suppressed the agglomeration of Ni, and promoted the anode durability. XRD analysis suggested the formation of a nitride CrN during operation in the Ni97–Cr3/SDC anode, and the role of the nitride was discussed in detail., Solid State Ionics, 319180 - 185, 01 Jun. 2018, English, Research paper (scientific journal) - Solvation-controlled ester-based concentrated electrolyte solutions for high-voltage lithium-ion batteries
Takayuki Doi, Michihiro Hashinokuchi, Minoru Inaba
© 2018 Elsevier B.V. Highly concentrated electrolyte solutions exhibit high stability against oxidation, and hence have a high potential for the high voltage operation of lithium-ion batteries (LIBs). However, they are highly viscous and very costly due to an extensive use of lithium salts. These problems were solved by diluting the highly concentrated electrolyte solutions with a diluent that has a low donor number, a high miscibility, and a high stability against oxidation. The resultant electrolyte solutions suppressed the degradation of 5 V-class LiNi0.5Mn1.5O4positive-electrodes upon repeated charge/discharge cycling, and extended the reversible capacity of LiNi0.5Co0.2Mn0.3O2electrodes to ca. 200 mAh g−1by charging to a high voltage of 4.6 V., Current Opinion in Electrochemistry, 949 - 55, 01 Jun. 2018, English - Morphology changes and long-term cycling durability of Si flake powder negative electrode for lithium-ion batteries
Masakazu Haruta, Ryuya Hioki, Takashi Moriyasu, Akira Tomita, Toshio Takenaka, Takayuki Doi, Minoru Inaba
© 2018 Elsevier Ltd Silicon flake powder (Si LeafPowder®, Si-LP) with the thickness and lateral dimension of 100 nm and 3–5 μm, respectively, demonstrated superior cycle performance as a negative electrode in lithium-ion batteries. A multi-folded layered structure with many voids was spontaneously formed in Si-LP composite electrodes by morphology changes of Si-LP sheets in repeated charge and discharge cycles. The multi-folded layered structure accommodated volumetric changes of the Si active material and prevented exfoliation of the active material from the current collector, which led to the superior long-term cyclability of the Si-LP electrode. The main factor for capacity fading in long-term cycling was a gradual loss of conduction pathways between Si-LP sheets due to the accumulation of electrolyte reduction products in the electrode. The film-forming additives, vinylene carbonate and fluoroethylene carbonate, effectively suppressed the electrolyte decomposition and remarkably improved the cycle performance of the Si-LP electrode., Electrochimica Acta, 26794 - 101, 20 Mar. 2018, English, Research paper (scientific journal) - Enhancement of Oxygen Reduction Reaction Activity of Pd Core-Pt Shell Structured Catalyst on a Potential Cycling Accelerated Durability Test
Naoya Aoki, Hideo Inoue, Takashi Okawa, Takashi Okawa, Yuta Ikehata, Yuta Ikehata, Akira Shirai, Akira Shirai, Hideo Daimon, Takayuki Doi, Yuki Orikasa, Yuki Orikasa, Yoshiharu Uchimoto, Hiroshi Jinnai, Shin Inamoto, Yuji Otsuka, Minoru Inaba
© 2017, Springer Science+Business Media, LLC. Carbon-supported Pd core-Pt shell structured catalyst (Pt/Pd/C) was synthesized by a modified Cu under potential deposition/Pt displacement method without any precise potential control. The specific activity for oxygen reduction reaction (ORR) of the Pt/Pd/C catalyst increased by 5-fold after an accelerated durability test (ADT; rectangular wave potential cycling of 0.6 V (3 s)–1.0 V (3 s) performed in Ar-saturated 0.1 M HClO4at 80 °C for 10,000 cycles), which enhanced ORR mass activity of the catalyst by 1.4-fold although its electrochemical surface area significantly decreased. TEM observation showed that the morphology of the catalyst particles changed into a spherical shape and the mean diameter decreased after the ADT. TEM-EDX compositional analysis revealed that the Pd core preferentially dissolved out and that the Pt shell was rearranged and thickened with the ADT. CV measurement using Bi3+probe implied that the Pt(111) facet was partially formed on the Pt shell after the ADT. Furthermore, EXAFS analysis showed that the Pt–Pt bond distance of the Pt shell was shortened after the ADT. It was considered that the drastic enhancement in the ORR-specific activity of the catalyst after the ADT arises from the decrease in number of lowly coordinated surface Pt atoms, partially formed Pt(111) facet on the catalyst surface, and properly induced compressive strain in the Pt shell via the rearrangement of the Pt shell assisted by the preferential dissolution of the Pd core during the ADT. [Figure not available: see fulltext.]., Electrocatalysis, 9125 - 138, 01 Mar. 2018, English, Research paper (scientific journal) - Pre-film formation and cycle performance of silicon-flake-powder negative electrode in a solvate ionic liquid for silicon-sulfur rechargeable batteries
Haruta Masakazu, Takashi Moriyasu, Akira Tomita, Toshio Takenaka, Takayuki Doi, Minoru Inaba
© 2018 The Electrochemical Society. In developing silicon-sulfur batteries with a high energy density, the cycle performance of a Si-flake-powder (Si LeafPowder, Si-LP) negative electrode in a solvate ionic liquid of lithium salt-glyme equimolar complex electrolyte were improved by stable pre-film formation on the Si-LP. The pre-film was formed by pre-cycling in a fluoroethylene carbonate-based electrolyte prior to cycle tests in the glyme-based electrolyte. The capacity retention of the pre-cycled Si-LP electrode in the glyme-based electrolyte improved remarkably. Surface deposition originating from decomposition products of the electrolyte decreased by formation of the pre-film. The pre-film consisted of fine LiF grains and organo-fluorine compounds, the combination of which is important for inhibiting decomposition of the glyme-based electrolyte on Si negative electrodes., Journal of the Electrochemical Society, 165A1874 - A1879, 01 Jan. 2018, English, Research paper (scientific journal) - Low-Viscosity γ-Butyrolactone-Based Concentrated Electrolyte Solutions for LiNi
0.5 Mn1.5 O4 Positive Electrodes in Lithium-Ion Batteries
Takayuki Doi, Yusuke Shimizu, Michihiro Hashinokuchi, Minoru Inaba
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Highly concentrated electrolyte solution with a low viscosity and high stability against oxidation was obtained by using a single solvent system of LiBF4/γ-butyrolactone (GBL). Although up to 4.65 mol kg−1LiBF4could be dissolved in GBL at room temperature, 3.87 mol kg−1LiBF4/GBL was a reasonable compromise to attain a low viscosity (52.1 mPa s) and a low GBL/Li molar ratio (3.00). Sodium carboxymethylcellulose and poly(acrylic acid) were used as binders for the spinel LiNi0.5Mn1.5O4positive electrode and the graphite negative electrode, respectively, to suppress the swelling of conventional poly(vinylidene fluoride)-based binder. The charge and discharge performances of the LiNi0.5Mn1.5O4positive electrode and the graphite negative electrode were improved by using 3.87 mol kg−1LiBF4/GBL, as compared with concentrated propylene carbonate-based electrolyte solution., ChemElectroChem, 42398 - 2403, 01 Sep. 2017, English, Research paper (scientific journal) - Electrochemical and Chemical Treatment Methods for Enhancement of Oxygen Reduction Reaction Activity of Pt Shell-Pd Core Structured Catalyst
Naoya Aoki, Hideo Inoue, Akira Shirai, Shunya Higuchi, Yuki Matsui, Hideo Daimon, Takayuki Doi, Minoru Inaba
© 2017 Elsevier Ltd Based on the accelerated durability test protocol (ADT, rectangular wave, 1.0 V (3 s)-0.6 V (3 s), 10,000 cycles, at 80 °C), a high activation protocol (HAP) was developed as an electrochemical treatment method using rectangular wave potential cycling for a carbon supported Pt shell-Pd core structured catalyst (Pt/Pd/C), which mitigated the decay of electrochemical surface area (ECSA) and enhanced the mass activity for oxygen reduction reaction (ORR). It was found that a longer holding time and a less cycle number (300 s and 30 cycles) compared with those used for the ADT protocol (3 s and 10,000 cycles) effectively suppressed the ECSA decay and enhanced the ORR mass activity. A potential in the range of 0.2 to 0.6 V was suitable as the lower limit potential of the HAP protocol for the ORR activity enhancement when the upper limit potential was fixed at 1.0 V. Furthermore, H2-O2and Cu-O2chemical treatment methods, which chemically realize the HAP performed on GC electrode, were developed, where the equilibrium potentials of Cu/Cu2+, hydrogen and oxygen were utilized for surface oxidation and reduction of Pd and Pt. Both methods mitigated the ECSA decay and enhanced the ORR mass activity, and the Cu-O2chemical treatment method gave a higher mass activity. These chemical treatment methods are useful for mass-production of highly active Pt core-shell structured catalyst., Electrochimica Acta, 244146 - 153, 01 Aug. 2017, English, Research paper (scientific journal) - Effect of infiltrated transition metals in Ni/Sm-doped CeO
2 cermet anode in direct NH3 -fueled SOFCs
M. Zhang, M. Hashinokuchi, R. Yokochi, T. Doi, M. Inaba
© The Electrochemical Society. The activity of transition metals (Cr and V) infiltrated Ni/Smdoped ceria (SDC) cermet anodes for NH3oxidation was investigated at 973 to 1173 K. The 3 at.% addition of Cr and V with respect to the total metal composition improved the anode activity for NH3oxidation. The relationship between the anode activity of the Ni-based binary anode and the metal-nitrogen binding energy of the added transition metal, which is a key to realize the highly active anode for direct NH3-fueled SOFCs, is discussed., ECS Transactions, 781517 - 1522, 30 May 2017, English, Research paper (international conference proceedings) - Enhanced activity and stability of Ni-based binary anode in direct NH
3 -fueled SOFCs
M. Hashinokuchi, M. Zhang, R. Yokochi, T. Doi, M. Inaba
© The Electrochemical Society. The activity and stability of Ni-based binary alloy anodes for direct ammonia-fueled SOFCs were investigated in the temperature range of 823 to 973 K. It was found that the activities of Ni40-Fe60and Ni97-Mo3/SDC anodes for ammonia oxidation were higher than Ni/SDC anode at temperature of 823 to 973 K. In addition, the Ni40-Fe60and Ni97-Mo3/SDC anodes exhibited higher stability in a heat cycle test between 873 and 973 K in ammonia atmosphere than the Ni/SDC anode. It was found that the change in the shape of the metal catalysts induced by the heat cycle was suppressed in the Ni40-Fe60and Ni97-Mo3/SDC anodes., ECS Transactions, 781495 - 1500, 30 May 2017, English, Research paper (international conference proceedings) - Temperature effects on SEI formation and cyclability of Si nanoflake powder anode in the presence of SEI-forming additives
Masakazu Haruta, Takashi Okubo, Yuta Masuo, Shuhei Yoshida, Akira Tomita, Toshio Takenaka, Takayuki Doi, Minoru Inaba
© 2016 Elsevier Ltd Silicon nanoflake powder (Si LeafPowder®, Si-LP) used as an anode material for lithium-ion batteries has demonstrated superior cycle performance at 30 °C in an ethylene-carbonate-based electrolyte solution because its characteristic thin-film-based structure resists pulverization. However, capacity fading was accelerated at 60 °C owing to enhanced decomposition of the electrolyte solution and growth of a solid electrolyte interface (SEI), which leads to loss of the electronic contact between Si-LP particles. The SEI-forming additives vinylene carbonate (VC), fluoroethylene carbonate (FEC), and difluoroethylene carbonate improved the capacity retention and Coulombic efficiency at 30 °C. Although VC is the most effective additive at 60 °C, the discharge capacity was decreased dramatically at −5 °C owing to poor ionic and electronic conductivity of the SEI layer formed from the VC-added electrolyte solution. The added FEC produced better performance in a wide temperature range of −5 to 60 °C because the SEI layer formed in the FEC-added electrolyte solution had higher ionic and electronic conductivity than that formed from VC, even at −5 °C. To obtain Si anodes with high discharge capacity and long cycle life, an appropriate choice of SEI-forming additive taking into account the operating temperature is important., Electrochimica Acta, 224186 - 193, 10 Jan. 2017, English, Research paper (scientific journal) - AdsorbedWater on Nano-Silicon Powder and Its Effects on Charge and Discharge Characteristics as Anode in Lithium-Ion Batteries
Shuhei Yoshida, Shuhei Yoshida, Yuta Masuo, Daisuke Shibata, Masakazu Haruta, Takayuki Doi, Minoru Inaba
© The Author(s) 2016. Published by ECS. The amounts of adsorbed water on several kinds of carbon and silicon materials including Si nano-flake powder (Si LeafPowder, Si-LP) were determined at 250?C. It was found that nano-sized Si materials adsorb a large amount of water even after being dried at 120?C because of the hydrophilicity of the surface and the high specific surface area. The adsorbedwater on Si-LP can be removed, but not completely, after drying at a 180°C. The charge and discharge characteristics of Si-LP, especially the initial irreversible capacity and the coulombic efficiencies upon repeated cycling, were significantly improved by removal of the adsorbed water at 180?C. The 180°C-dried sample also suppressed gas evolution during the initial charging and discharging cycle. From the results of gas analysis, it was found that gases evolved from the Si-LP electrodes were mainly H2and CO2. From the results of charge and discharge tests and gas analysis, the effect of the adsorbed water on the irreversible decomposition of the electrolyte solution was discussed., Journal of the Electrochemical Society, 164A6084 - A6087, 01 Jan. 2017, English, Research paper (international conference proceedings) - Suppression of Mn–Ion-Dissolution of LiNi
0.5 Mn1.5 O4 Electrodes in a Highly Concentrated Electrolyte Solution at Elevated Temperatures
Takayuki Doi, Yusuke Shimizu, Ryo Matsumoto, Michihiro Hashinokuchi, Minoru Inaba
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Mn-based active materials, such as LiMn2O4, are widely used for positive electrodes in lithium ion batteries, and spinel LiNi0.5Mn1.5O4is drawing much attention to realize 5-V class batteries. However, the oxidative decomposition of electrolyte solution at high voltages and Mn-dissolution of LiNi0.5Mn1.5O4are serious problems to be solved. These two drawbacks are more marked at elevated temperatures, and should be caused by free solvent molecules in electrolyte solution. In this study, highly concentrated electrolyte solution, which contains few free solvent molecules, was investigated to solve the problems. LiNi0.5Mn1.5O4electrodes worked at 50oC in nearly saturated 7.25 mol kg−1LiBF4/ propylene carbonate (PC) electrolyte solution, whereas not in the nearly saturated 4.30 mol kg−1LiPF6/PC. In addition, Mn-ion dissolution from LiNi0.5Mn1.5O4was significantly suppressed in highly concentrated electrolyte solutions, and correlated to the fraction of free PC molecules in them., ChemistrySelect, 28824 - 8827, 01 Jan. 2017, English, Research paper (scientific journal) - High rate charge and discharge characteristics of graphite/SiO
x composite electrodes
Shuhei Yoshida, Shuhei Yoshida, Takashi Okubo, Yuta Masuo, Yasuyuki Oba, Daisuke Shibata, Masakazu Haruta, Takayuki Doi, Minoru Inaba
© The Electrochemical Society of Japan, All rights reserved. Charge and discharge properties of a graphite/SiOxcomposite electrode were studied over a wide range of charge/ discharge rates (1/20 to 5C) for use in automotive applications. The graphite/SiOx(90/10 by weight) composite electrode gave a high reversible capacity (453mAh·g-1), and showed a good capacity retention at a low rate of 1/ 20 C. However, the capacity decreased significantly on cycling at a high rate of 2C. From the analysis of the charging and discharging processes, it was found that the charging reaction occurs predominantly at SiOxparticles initially at higher potentials and then proceeds at graphite particles at lower potentials to be fully charged. This tendency was also supported by a dependence of the activation energy of the charge transfer reaction on the state of charge (SOC) estimated by ac impedance analysis. Because the composite electrode contains only 10% SiOx, the current was excessively concentrated to the SiOxparticles at the initial state when charged at high rates. This caused crack formation in SiOxparticles, and the resulting contact loss between particles was considered as the reason for the observed poor cycleability at 2C., Electrochemistry, 85403 - 408, 01 Jan. 2017, English, Research paper (scientific journal) - Silicon nano-flake powder as an anode for the next generation lithium-ion batteries: Current status and challenges
Minoru Inaba, Masakazu Haruta, Morihiro Saito, Takayuki Doi
© The Electrochemical Society of Japan, All rights reserved. Silicon is electrochemically alloyed and de-alloyed with Li at potentials close to Li+/Li and is widely recognized as the most promising candidate for the anode of LIBs with a high energy density (250-300Whkg-1) in the next generation. The most serious issue of Si anode is poor capacity retention owing to large volume changes during charging and discharging. We developed Si LeafPowder® with a nano-flake structure to overcome the poor capacity retention. However Si anodes still have some problems such as large irreversible capacity, ceaseless electrolyte decomposition, swelling of the electrode, etc. for use in high-energy density LIBs in the next generation. In this article, these problems and the challenges to mitigate them are overviewed based on our resent data obtained by Si nano-flakes (Si LeafPowder®)., Electrochemistry, 85623 - 629, 01 Jan. 2017, English, Research paper (scientific journal) - Dilution of highly concentrated libf4/propylene carbonate electrolyte solution with fluoroalkyl ethers for 5-V LiNi
0.5 Mn1.5 O4 positive electrodes
Takayuki Doi, Yusuke Shimizu, Michihiro Hashinokuchi, Minoru Inaba
© The Author(s) 2017. Published by ECS. Various kinds of fluoroalkyl ethers were investigated as diluents to reduce the high viscosity of highly concentrated LiBF4/PC electrolyte solutions. 1,1,2,2-Tetrafluoroethyl 2,2,3,3-Tetrafluoropropyl ether (HFE) was the most suitable diluent because of a high solubility of LiBF4. 2.50 mol kg-1 LiBF4/PC+HFE (2:1 by volume) was a reasonable compromise to attain a low viscosity (51.7 mPa s) and a low PC/Li molar ratio (2.39). Raman spectroscopy revealed that the fraction of free PC molecules in 2.50 mol kg-1 LiBF4/PC+HFE (2:1) was much smaller than 2.50 mol kg-1 LiBF4/PC (PC/Li molar ratio = 4.00), and that the interactions of HFE with Li+ cations and BF4 -Anions were very weak. LiNi0.5Mn1.5O4positive electrodes showed high charge/discharge performance with low irreversible capacities in 2.50 mol kg-1 LiBF4/PC+HFE (2:1), which showed that the highly concentrated LiBF4/PC system can be diluted with HFE without losing the high stability against oxidation., Journal of the Electrochemical Society, 164A6412 - A6416, 01 Jan. 2017, English, Research paper (international conference proceedings) - Suppression of manganese-ion dissolution by sio
2 aerosol addition from spray pyrolyzed li2mno3 -limn1/3 ni1/3 co1/3 o2
Satoshi Hashigami, Satoshi Hashigami, Masayuki Kawanishi, Kei Yoshimi, Satoshi Ujiie, Toru Inagaki, Michihiro Hashinokuchi, Takayuki Doi, Minoru Inaba
© The Electrochemical Society of Japan, All rights reserved. Layered Li2MnO3-LiMn1/3Ni1/3Co1/3O2solid-solution cathode materials modified with SiO2were prepared by spra pyrolysis and their charge-discharge properties were investigated. Both the capacity and voltage fades of SiO2modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2during charge/discharge cycling were suppressed compared with that of th unmodified sample. It was found that the addition of SiO2suppressed the dissolution of manganese ions at 60° from the results of inductively coupled plasma (ICP) emission spectroscopy. X-ray diffraction (XRD) data indicate that weak reflections corresponding to Li2SiO3appeared as the SiO2content increases to 5wt%. Scanning electro microscope (SEM) studies showed that the microstructure of the particles was significantly changed by SiO addition. As indicated by transmission electron microscope (TEM) analysis, Si-rich regions were seen on th Li2MnO3-LiMn1/3Ni1/3Co1/3O2primary particles. The suppression of Mn ions and the improved charge and discharg properties were correlated with the microstructural changes., Electrochemistry, 84842 - 847, 01 Nov. 2016, English, Research paper (scientific journal) - Si/li
2 s battery with solvate ionic liquid electrolyte
Zhe Li, Yutaro Kamei, Masakazu Haruta, Toshio Takenaka, Akira Tomita, Takayuki Doi, Shiguo Zhang, Kaoru Dokko, Minoru Inaba, Masayoshi Watanabe
© The Electrochemical Society of Japan, All rights reserved. A lithium-sulfur cell was developed, consisting of a Si nanoflake negative electrode, a Li2S/graphene positiv electrode, and a non-flammable solvate ionic liquid electrolyte. This cell configuration allows us to avoid the use o Li metal electrode and the concomitant dendritic deposition of Li metal at the negative electrode during charging thereby rendering the cell operation highly safe and stable. The solvate ionic liquid electrolyte solution wa composed of tetraglyme, lithium bis(trifluoromethanesulfonyl)amide, and a hydrofluoroether. The solubility o lithium polysulfide (reaction intermediate of the positive electrode) is very low, resulting in high Coulombi efficiency of discharge/charge and long cycle life of the Si/Li2S cell., Electrochemistry, 84887 - 890, 01 Nov. 2016, English, Research paper (scientific journal) - 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, Susumu Kuwabata
© The Author(s) 2016. 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 SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data., Scientific Reports, 6, 26 Oct. 2016, English, Research paper (scientific journal) - Concentrated LiPF
6 /PC electrolyte solutions for 5-V LiNi0.5 Mn1.5 O4 positive electrode in lithium-ion batteries
Takayuki Doi, Rin Masuhara, Michihiro Hashinokuchi, Yusuke Shimizu, Minoru Inaba
© 2016 Elsevier Ltd Charge and discharge properties of spinel LiNi0.5Mn1.5O4positive electrodes were investigated using propylene carbonate (PC)-based concentrated electrolyte solutions in the range of 0.83 (ca. 1 mol dm−3) to 4.45 (nearly saturated) mol kg−1. The solvation state of PC in the concentrated electrolyte solution was studied by Raman spectroscopy. The HOMO energy of PC in Li+(PC)nwas evaluated by first-principle calculation to assess the oxidative stability of PC molecules solvating lithium ion. Charge and discharge measurements revealed that the irreversible capacity due to solvent decomposition decreased with increasing the concentration of LiPF6, while discharge capacity increased. In addition, cycle performance of LiNi0.5Mn1.5O4positive electrodes was remarkably improved by the use of graphitized Ketjenblack as a conductive additive., Electrochimica Acta, 209219 - 224, 10 Aug. 2016, English, Research paper (scientific journal) - Enhancement of anode activity at Ni/Sm-doped CeO
2 cermet anodes by Mo addition in NH3 -fueled solid oxide fuel cells
Michihiro Hashinokuchi, Ryuji Yokochi, Wataru Akimoto, Takayuki Doi, Minoru Inaba, Junichiro Kugai
© 2015 Elsevier B.V. All rights reserved. Molybdenum was added to nickel/Sm2O3-doped ceria (Ni/SDC) cermets by a MoCl5impregnation method, and the activity of the resulting Ni-Mo/SDC cermets was evaluated as anodes in ammonia-fueled solid oxide fuel cells (SOFCs) in the temperature range of 973-1173 K. It has been revealed that the addition of Mo improved remarkably the catalytic activity for NH3reforming and enhanced the cell performance. The Ni-Mo/SDC anode with a Mo content of ~ 3 atomic % of the total metal showed the highest catalytic activity for NH3reforming. XRD analysis of a NiO-MoO3powder mixture annealed in NH3revealed the formation of a nitride NixMo1-xN during operation of Ni-Mo/SDC anodes, and the role of the nitride in NH3reforming was discussed in detail., Solid State Ionics, 285222 - 226, 01 Feb. 2016, English, Research paper (scientific journal) - Synthesis of SiO
2 -modified Li2 MnO3 -LiMn1/3 Ni1/3 Co1/3 O2 by spray pyrolysis with acid addition as cathode materials for lithium ion batteries
Satoshi Hashigami, Satoshi Hashigami, Kei Yoshimi, Masayuki Kawanishi, Satoshi Ujiie, Toru Inagaki, Michihiro Hashinokuchi, Takayuki Doi, Minoru Inaba
© The Electrochemical Society. SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2cathode materials for lithium ion batteries were synthesized by a spray pyrolysis technique using starting solutions containing citric acid and boric acid. SEM images showed that most of the particles using citric acid had spherical shapes and thin shell structures. Some particles were collapsed when the amount of citric acid was large. The specific surface area of the particles prepared from the citric acid-added solution was higher than that without citric acid. The addition of boric acid decreased the specific surface area of the material by acting as a sintering agent. The charge and discharge capacities for the synthesized materials were investigated and it was found that the addition of citric acid, which gave a higher specific surface area, enhanced the rate capability., ECS Transactions, 7311 - 17, 01 Jan. 2016, English, Research paper (international conference proceedings) - LiBF
4 -Based concentrated electrolyte solutions for suppression of electrolyte decomposition and rapid lithium-ion transfer at LiNi0.5 Mn1.5 O4 /electrolyte interface
Takayuki Doi, Yusuke Shimizu, Michihiro Hashinokuchi, Minoru Inaba
© 2016 The Electrochemical Society. Charge and discharge properties of spinel LiNi0.5Mn1.5O4positive electrodes were investigated using concentrated LiBF4/propylene carbonate (PC) electrolyte solutions in the range of 0.833 (ca. 1 mol dm-3) to 7.25 (nearly saturated) mol kg-1. The irreversible decomposition of electrolyte solution was effectively suppressed with an increase in concentration. In addition, the polarization in charge/discharge reactions remained small in the nearly saturated 7.25 mol kg-1LiBF4/PC even though the viscosity was very high and the ionic conductivity was low. The rate capability was higher than that obtained with nearly saturated 4.3 mol kg-1LiPF6/PC. The structure, viscosity, and ionic conductivity of the concentrated LiBF4/PC were investigated. Based on the experimental results, the rapid charge/discharge reactions at LiNi0.5Mn1.5O4electrodes were discussed., Journal of the Electrochemical Society, 163A2211 - A2215, 01 Jan. 2016, English, Research paper (scientific journal) - Analysis of the Ionic Conduction Behavior in a Few of Room Temperature Molten Fluorides
Akimasa Tasaka, Akimasa Tasaka, Hidemi Inoue, Tomohiro Isogai, Takaaki Nakai, Saito Morihiro, Saito Morihiro, Minoru Inaba, Minoru Inaba
© 2015 Elsevier Ltd. All rights reserved. The average self-diffusion coefficients of cations and anions increased with increasing the HF-concentration and temperature in (CH<inf>3</inf>)<inf>3</inf>N·mHF, (CH<inf>3</inf>)<inf>4</inf>NF·mHF, (C<inf>2</inf>H<inf>5</inf>)<inf>3</inf>N·mHF, and (C<inf>2</inf>H<inf>5</inf>)<inf>4</inf>NF·mHF melts. The behavior of the self-diffusion coefficients of cations and anions in every melt is in good agreement with an increase in ionic conductivity and a decrease in viscosity. The transference number of (FH)<inf>n</inf>F<sup>-</sup> anions estimated from the values of self-diffusion coefficients for each ion in every melt was almost constant and their values were around 0.6 in the (CH<inf>3</inf>)<inf>3</inf>N·mHF melt and around 0.7 in the (CH<inf>3</inf>)<inf>4</inf>NF·mHF, the (C<inf>2</inf>H<inf>5</inf>)<inf>3</inf>N·mHF, and the (C<inf>2</inf>H<inf>5</inf>)<inf>4</inf>NF·mHF melts. The value of theoretical conductivity (σ<inf>NMR</inf>) obtained from the average self-diffusion coefficients of cations and anions by using Nernst-Einstein equation was higher than the value of experimental ionic conductivity (σ). Therefore, it is concluded that the diffusion of (FH)<inf>n</inf>F<sup>-</sup> anions is faster than that of each cation in every melt and that a part of both cation and anion in each melt may associate by interaction between both ions., Electrochimica Acta, 174721 - 727, 26 Jun. 2015, English, Research paper (scientific journal) - Effects of nitride formation on anode catalytic activity in ammonia-fueled SOFCs
Ryuji Yokochi, Michihiro Hashinokuchi, Takayuki Doi, Minoru Inaba
© The Electrochemical Society. Four kinds of anodes, Ni-Mo(3%)/, Ni-W(3%)/, Ni-Ta(3%)/ and Ni-Nb(3%)/Sm<inf>0.2</inf>Ce<inf>0.8</inf>O<inf>2</inf> (SDC) were prepared by impregnating Mo, W, Ta and Nb precursor solutions into pre-sintered Ni/SDC cermets. Their anode performance was evaluated in ammonia-fueled SOFCs at 973-1173 K to clarify the correlation between nitride formation and anode activity. The addition of Mo, W and Ta enhanced the anode activity for NH<inf>3</inf> oxidation, but Nb did not. Under the operation conditions (i.e. at 973-1173 K in NH<inf>3</inf>), MoO<inf>3</inf>, WO<inf>3</inf> and Ta<inf>2</inf>O<inf>5</inf> reacted with NH<inf>3</inf> to form nitrides (Mo<inf>2</inf>N, W<inf>2</inf>N and TaON), but Nb<inf>2</inf>O<inf>5</inf> did not. These results suggest that the easiness of the nitride formation is closely related to the high activity anode for NH<inf>3</inf> oxidation., ECS Transactions, 682745 - 2750, 01 Jan. 2015, English, Research paper (international conference proceedings) - Development of highly active and durable platinum core-shell catalysts forpolymer electrolyte fuel cells
Minoru Inaba, Hideo Daimon
© 2015, Japan Petroleum Institute. All rights reserved. Polymer electrolyte fuel cells (PEFCs) are clean and highly efficient energy sources without emission of global warming CO<inf>2</inf> gas, and have been developed as electric power sources in fuel cell vehicles (FCVs). One of the most important issues in the development of PEFCs is currently a drastic reduction of Pt usage by an improvement in the activity for oxygen reduction reaction at the Pt cathode catalyst. To improve the activity of the Pt catalyst, we have so far developed core-shell catalysts using Pt monolayer shell covered on Au or Pd core materials. In this review article, a novel preparation method for Pt monolayer formation on non-Pt core nanoparticles that is suitable for mass production of the core-shell catalysts, and the results on the activity and durability of the resulting core-shell catalysts are overviewed. The potentials and difficulties of the core-shell catalysts for use in practical FCVs are discussed., Journal of the Japan Petroleum Institute, 5855 - 63, 01 Jan. 2015, English - Cycle performances of si-flake-powder anodes in lithium salt-tetraglyme complex electrolytes
Masakazu Haruta, Yuta Masuo, Takashi Moriyasu, Akira Tomita, Chihiro Sakakibara, Akika Kamei, Masato Hirota, Toshio Takenaka, Takayuki Doi, Minoru Inaba
© The Electrochemical Society of Japan, All rights reserved. Charge and discharge properties of amorphous Si nano-flake powder (Si Leaf Powder, Si-LP) in lithium bis(trifluoromethanesulfonyl)amide-tetraglyme complex electrolyte, [Li(G4)][TFSA], were investigated for use as an anode in silicon-sulfur battery. Though a high reversible capacity (2,300-2,700mAhg?1) was obtained initially in [Li(G4)][TFSA], the overpotential gradually increased upon cycling. The increase in overpotential was reduced by dilution with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The addition of fluoroethylene carbonate (FEC) further reduced the overpotential and improved cycleability. Electrochemical impedance spectroscopy analysis revealed that the observed improvements in charge and discharge characteristics are due to the formation of solid electrolyte interface layer with a high ionic-conductivity in the presence of FEC., Electrochemistry, 83837 - 839, 01 Jan. 2015, English, Research paper (international conference proceedings) - Li pre-doping of amorphous silicon electrode in li-naphthalene complex solutions
Shuhei Yoshida, Shuhei Yoshida, Yuta Masuo, Daisuke Shibata, Masakazu Haruta, Takayuki Doi, Minoru Inaba
© The Electrochemical Society of Japan, All rights reserved. To compensate a large initial irreversible capacity (Qirr) of silicon electrode, a novel Li pre-doping technique using Linaphthalene complex/tetrahydrofuran solutions was developed. Li was successfully doped to amorphous silicon nano-flake particles, and the doping level of Li was easily controlled by adjusting naphthalene concentration. A large Qirrof the pristine electrode (1200mAhg?1) was almost completely compensated after pre-doped in 0.1 moldm?3 Li-naphthalene solution for 1 h. In addition, no harmful effects of pre-doping on cycleability were observed., Electrochemistry, 83843 - 845, 01 Jan. 2015, English, Research paper (international conference proceedings) - Preparation and charge/discharge characteristics of carbon-modified ramsdellite TiO
2 as a high potential anode
Ryotaro Kanazawa, Masakazu Haruta, Takayuki Doi, Minoru Inaba
© The Electrochemical Society of Japan, All rights reserved. Carbon-modified ramsdellite titanium dioxide, TiO2(R), was prepared without using metallic Ti powder, and its charge and discharge properties was investigated as an anode of lithium ion batteries. Carbon sources (citric acid and multi-walled carbon nanotubes) were added in the calcination process to obtain a LiTi2O4precursor. The carbon addition was indispensable to obtain stoichiometric LiTi2O4 as a precursor and the resulting Li+-free TiO2(R). The carbon-modified TiO2(R) had a round shape and a smaller particle size of 0.5-1.5?m. The discharge capacity and rate-capability were improved by carbon modification due to an enhancement of the electronic conductivity and a reduction of the lithium-ion diffusion path., Electrochemistry, 83867 - 869, 01 Jan. 2015, English, Research paper (international conference proceedings) - Mechanism and activity of Ni-based (Ni-M: M = Fe, Mo, W, Ta) cermet anodes for ammonia oxidation in SOFCs
M. Hashinokuchi, R. Yokochi, W. Akimoto, T. Doi, M. Inaba, J. Kugai
© The Electrochemical Society. We investigated the activity for Ni-based (Ni-M: M = Mo, W and Ta) anodes for ammonia oxidation in SOFCs. It was found that Mo was the most effective additive for the anode cermets in this study. It was found that the activity for ammonia oxidation at Ni-Mo anode was determined by a balance between ammonia adsorption and nitrogen desorption, and synergetic effects of Ni and Mo improved the anode activity for NH<inf>3</inf> oxidation., ECS Transactions, 682739 - 2744, 01 Jan. 2015, English, Research paper (international conference proceedings) - Effects of Li pre-doping on charge/discharge properties of Si thin flakes as a negative electrode for Li-ion batteries
Takashi Okubo, Morihiro Saito, Chihiro Yodoya, Akika Kamei, Masato Hirota, Toshio Takenaka, Toyoki Okumura, Akimasa Tasaka, Minoru Inaba
To compensate the large irreversible capacity (Qirr), lithium was pre-doped to Si thin flakes (Si Leaf Powder® (Si-LP), thickness: 100 nm) for different times, and its effects on the charge/discharge characteristics such as reversible capacity, cycleability, and rate-capability were investigated in detail. The charge/discharge test results showed that a large initial Qirrof ca. 2300 mAh g- 1for the Si-LP can be completely compensated by Li pre-doping, and a high capacity (> 2500 mAh g- 1) was obtained for pre-doped Si-LPs. The pre-doping did not cause any harmful effects on cycleability as long as lithium was uniformly pre-doped. The addition of vinylene carbonate to the electrolyte solution in the pre-doping and in the test cell greatly improved the cycleability, and a high discharge capacity of ca. 2300 mAh g- 1was kept after 40 cycles. © 2013 Elsevier B.V., Solid State Ionics, 26239 - 42, 01 Sep. 2014, English, Research paper (scientific journal) - Effects of Temperature and Boron Concentration of a Boron-Doped Diamond (BDD) Electrode on NF
3 Current Efficiency, and Stability of BDD Electrode in Molten NH4 F·2HF
A. Tasaka, A. Tasaka, Y. Iida, T. Shiono, M. Uno, Y. Nishiki, T. Furuta, M. Saito, M. Inaba, M. Inaba
© 2014 John Wiley & Sons, Ltd. The current efficiency for NF3formation was independent of the current density in the range of 200-1000mAcm-2. The average values of NF3current efficiencies on a boron-doped diamond (BDD) anode with a boron concentration of 2500ppm were 32.3% at 80°C, 63.3% at 100°C, and 59.7% at 120°C. The best current efficiencies for NF3formation on the BDD anode with boron concentrations of 2500, 5000, and 7500ppm were obtained at 100°C and those were 63.3, 73.3, and 56.2%, respectively. Although an anode effect occurred on BDD electrodes whose surface was partly covered with the spiculate structure, which had boron concentrations higher than 7500ppm, it did not take place on BDD electrodes whose surface was covered with the diamond structure, even if the BDD electrode had a boron concentration of 8000ppm., Molten Salts Chemistry and Technology, 9781118448731123 - 131, 23 Jun. 2014, English - Electrolytic Synthesis of (CF
3 )3 N from a Room Temperature Molten Salt of (CH3 )3 N·mHF with BDD Electrode
A. Tasaka, A. Tasaka, K. Ikeda, N. Osawa, M. Saito, M. Uno, Y. Nishki, T. Furuta, M. Inaba, M. Inaba
© 2014 John Wiley & Sons, Ltd. The electrolytic synthesis of (CF3)3N using a BDD anode from the room temperature molten salt of (CH3)3N·mHF (m=3.0, 4.0, and 5.0) and mixed melts of (CH3)3N · 5.0HF and CsF · 2.3HF were investigated. When the (CH3)3N·mHF (m=3.0, 4.0, and 5.0) melts without CsF were electrolyzed using a BDD anode, the yield of (CF3)3N was low and the main product was a partially fluorinated amine such as (CF3)2CHF2N. In the mixed melt of (CH3)3N·5.0HF+70wt% CsF · 2.3HF, the yield of (CF3)3N became higher in comparison with that obtained in electrolysis of the (CH3)3N · 5.0HF melt. This may be caused by an increase in the viscosity due to an increase in the electrostatic interaction between species such as HF, anion, a partially fluorinated tertiary ammonium cation, and a partially fluorinated compound by adding CsF · 2.3HF to a (CH3)3N·5.0HF melt, resulting in an increase in retention time of partially fluorinated tertiary amines with polarity in the mixed melt., Molten Salts Chemistry and Technology, 9781118448731351 - 358, 23 Jun. 2014, English - Ni-Fe/Sm-doped CeO
2 anode for ammonia-fueled solid oxide fuel cells
Wataru Akimoto, Tadashi Fujimoto, Morihiro Saito, Minoru Inaba, Hiroyuki Yoshida, Toru Inagaki
Anode cermets using various transition metals (Ni, Co, and Fe) and Ce0.8Sm0.2O2 - σ(SDC) were prepared and their catalytic activity for ammonia oxidation in solid oxide fuel cells (SOFCs) was investigated. Ni/SDC showed a high activity for hydrogen, but not for ammonia. Co/SDC showed a poor activity for both hydrogen and ammonia. Fe/SDC has the highest activity for ammonia oxidation in the temperature range of 973 to 1173 K. Moreover, it was found that Ni-Fe alloy/SDC anodes showed improved performance for ammonia oxidation. Ni40-Fe60/SDC anode showed the highest catalytic activity for NH3oxidation, and therefore is promising for ammonia-fueled SOFCs. © 2013 Elsevier B.V. All rights reserved., Solid State Ionics, 2561 - 4, 01 Mar. 2014, English, Research paper (scientific journal) - Controllable growth orientation of Ag
2 O and Cu2 O films by electrocrystallization from aqueous solutions
Tsutomu Shinagawa, Yuya Ida, Kotaro Mizuno, Seiji Watase, Mitsuru Watanabe, Minoru Inaba, Akimasa Tasaka, Masanobu Izaki
We demonstrate that Ag2O and Cu2O polycrystal films with a cubic cuprite structure can be grown on F:SnO2 substrates with controllable crystal orientation between 111 and 100 directions by galvanostatic electrocrystallization from aqueous electrolytes. The Ag 2O and Cu2O films have been electrodeposited at different applied current densities determined by linear-sweep voltammetry (LSV) measurements, and their crystal structure and morphology were characterized with X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD results show the preferred growth orientation changed from 111 to 100 with increasing and decreasing current density for Ag2O and Cu2O, respectively. The surface morphology, especially for the Cu2O films, was also changed from a three-sided pyramidal shape to a four-sided pyramidal shape corresponding to the orientation. We also give a reasonable explanation for the observed trend in the growth orientation by considering the formation rate of AgOH and CuOH; higher and lower rates appear to yield 111 and 100 preferred orientation, respectively. © 2012 American Chemical Society., Crystal Growth and Design, 1352 - 58, 02 Jan. 2013, English, Research paper (scientific journal) - Improvement of tap density of TiO
2 (B) powder as high potential negative electrode for lithium ion batteries
Morihiro Saito, Yoshiyuki Nakano, Mikihiro Takagi, Naoki Honda, Akimasa Tasaka, Minoru Inaba
To improve the tap density of TiO2(B) as a high potential negative electrode for lithium-ion batteries, the particle size and the shape of the TiO2(B) were controlled by a new synthetic method using large-size Nbdoped rutile TiO2as a starting material. The Nb-doped TiO2(B) particles, Ti0.93Nb0.07O2(B) and Ti0.90Nb0.10O2(B), were much smaller (diameter: ca. 100 nm, length: ca. 800 nm) than the conventional TiO2(B) prepared using fine anatase TiO2particles as a starting material, and were agglomerated to form secondary particles with a diameter of 3-30 mm. The tap densities of Ti0.93Nb0.07O2(B) and Ti0.90Nb0.10O2(B) were successibly high (0.77 and 0.66 g cm-3, respectively), which were ca. 2-fold higher than that of the conventional TiO2(B) (0.30 g cm-3). As a result, the discharge capacity per electrode volume was significantly improved for both Nb-doped samples without sacrificing the cycleability. Non-doped TiO2(B) was prepared from large-size rutile TiO2by a similar method, but it deteriorated upon cycling, accompanied by the formation of the anatase phase. It was shown that Nb-doping not only improves the discharge capacity per electrode volume, but also effectively stabilizes the TiO2(B) crystal structure of the small particles. © 2013 Elsevier B.V. All rights reserved., Journal of Power Sources, 24450 - 55, 01 Jan. 2013, English, Research paper (scientific journal) - Synthesis and electrochemical properties of carbon-coated Li 2FeP2O7 for li-ion batteries
Morihiro Saito, Sosuke Yano, Takuma Maekawa, Akimasa Tasaka, Minoru Inaba
Carbon-coated Li2FeP2O7 (Li 2FeP2O7-C) and Mg-doped Li2FeP 2O7-C were successfully synthesized with pitch as a carbon source and Mg(C2O4)-H2O as a Mg source, and the charge/discharge properties were compared with that of bare Li 2FeP2O7. A thin carbon layer (ca. 5 nm in thickness) was coated on Li2FeP2O7 powder after heat-treatment. Li2FeP2O7-C and Mgdoped Li2FeP2O7-C exhibited high discharge capacities of 97 and 104 mAh g-1, respectively, at C/10 rate, implying a great improvement from that of bare Li2FeP2O7 (69 mAh g-1). The cycleability and rate-capability were also improved by carboncoating and Mg doping. Mg-doped Li2FeP2O7-C kept a high discharge capacity of 88 mAh g-1 even at 1 C rate. AC impedance analysis revealed that Mg-addition suppresses excess electrolyte decomposition on the surface of Li2FeP2O7 and reduces the resistance of SEI. © The Electrochemical Society., ECS Transactions, 50251 - 259, 01 Dec. 2012, English, Research paper (international conference proceedings) - Improvement of tap density of TiO2(B) powder as high potential negative electrode
Yoshiyuki Nakano, Kanji Masuda, Mikihiro Takagi, Morihiro Saito, Akimasa Tasaka, Minoru Inaba
The shape and size of TiO2(B) particles were controlled by ballmilling K2Ti4O9, H2Ti4O9 and TiO2(B) powders to improve the tap density of TiO2(B). It was found that only K2Ti4O9 endured the ball-milling process and provided a fine TiO2(B) powder after the ion-exchange and dehydration processes. In contrast, ball-milling of H2Ti4O9 and TiO2(B) powders resulted in a formation of a large amount of the rutile and anatase phase, respectively. In addition, a reduction of the spinning rate to 600 rpm suppressed the formation of the minor impurity of the anatase phase in the TiO2(B) sample prepared from the milled K2Ti4O9 powder. The resulting TiO2(B) (M1-600) powder exhibited a high tap density of 0.71 g cm-3 and a high electrode density of 1.25 g cm-3, which were 2.37 and 1.29 times, respectively, higher than those of the pristine TiO2(B). In charge/discharge tests, M1-600 exhibited a discharge of 213.1 mAh g-1, which is higher than that of the pristine TiO2(B), with a good cycleability. It gave a discharge capacity of 80.1 mAh g-1 even at a high rate of 10 C. © The Electrochemical Society., ECS Transactions, 50261 - 269, 01 Dec. 2012, English, Research paper (international conference proceedings) - Improvement of cycleability for Li-Si alloy anodes using Si thin flakes for Li-ion batteries
Tomoyuki Yamada, Morihiro Saito, Chihiro Yodoya, Akika Kamei, Masato Hirota, Toshio Takenaka, Akimasa Tasaka, Minora Inaba
Pure Si thin flakes (Si Leaf Powder® (Si-LP)) of different thicknesses (50, 100, 200, 300 and 400 nm) were prepared, and their charge/discharge properties were investigated as anode materials for lithium ion batteries (LIBs). Thickness of the thin Si-LP (100 nm) changed reversibly during charging and discharging, while the expanded thickness upon charging was kept after fully discharged for the thick one (300 nm), indicating insufficient Li de-alloying at C/6 rate. The slower kinetics for the thicker Si-LPs was also confirmed by examination of the open circuit potential (OCP) and the rate capability. These suggested that Li atoms diffused easily within the thinner Si-LPs and the uniform Li distribution suppressed the physical stress due to the Li alloying and de-alloying, resulting a good cycleability. In addition, addition of vinylene carbonate (VC) in electrolyte reduced charge transfer resistance of the Li alloying/de-alloying reaction and much more improved the cycleability of Si-LPs. ©The Electrochemical Society., ECS Transactions, 4127 - 35, 01 Dec. 2012, English, Research paper (international conference proceedings) - Electrolytic production of (CF
3 )3 N from room-temperature molten fluoride of (CH3 )3 N · 3HF using LaNiO3 coated Ni sheet anode
N. Osawa, M. Saito, M. Inaba, A. Tasaka
The LaNiO3coated Ni sheet anodes prepared by sol-gel coating method was developed to improve the Ni sheet anode for electrolytic synthesis of perfluorotrimethylamine, (CF3)3N, using the (CH3)3N·3HF melt as the electrolyte. The LaNiO3films may give the electric conductivity to the Ni sheet anode during electrolysis of the (CH3)3N·3HF melt. (CF3)3N was successfully obtained at a ratio of about 62 and 55% together with other partially fluorinated gaseous products. ©The Electrochemical Society., ECS Transactions, 4161 - 67, 01 Dec. 2012, English, Research paper (international conference proceedings) - Analysis of cationic structure in some room-temperature molten fluorides and dependence of their ionic conductivity and viscosity on hydrofluoric acid concentration
Tomohiro Isogai, Takaaki Nakai, Hidemi Inoue, Kenta Nakanishi, Shinji Kohara, Morihiro Saito, Minoru Inaba, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
To understand the ionic and nonionic species in (CH3)4NF·mHF, (CH3)3N·mHF, (C2H5)4NF·mHF, and (C2H5)3N·mHF melts, the structures of these melts were investigated by infrared spectroscopy, NMR, and high-energy X-ray diffraction. Infrared spectra revealed that three kinds of fluorohydrogenate anions, (FH)nF-(n = 1, 2, and 3), and molecular hydrofluoric acid (HF) are present in every melt. Ionic conductivity and viscosity of these melts were measured and correlated with their cationic structure. The ionic conductivity of the R4N+-systems was higher than that of corresponding R3NH+-systems because a strong N-H⋯F(HF)ninteraction prevents the motion of R3NH+cations in the R3N·mHF melts. (CH3)4N+and (CH3)3NH+cations gave higher ionic conductivity than (C2H5)4N+and (C2H5)3NH+cations, respectively, because the ionic radii of former cations were smaller than those of latter. It was concluded that these effects on ionic conductivity can be explained by the cationic structure and the concentration of molecular HF in the melts. © 2011 American Chemical Society., Journal of Physical Chemistry B, 1159593 - 9603, 11 Aug. 2011, English, Research paper (scientific journal) - Performances of metal fluoride added carbon anodes with pre-electrolysis for electrolytic synthesis of NF
3
Tomohiro Isogai, Tomohiro Isogai, Kazuhiro Hirooka, Tetsuro Tojo, Hitoshi Takebayashi, Morihiro Saito, Minoru Inaba, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
Metal fluoride added carbon anodes treated by pre-electrolysis were investigated for electrolytic production of nitrogen trifluoride (NF3) in molten NH4F·KF·4HF at 100 °C. The conditions for pre-electrolysis were first optimized using a graphite sheet anode as a model anode. The formation of fluorine-graphite intercalation compounds (fluorine-GICs) with semi-covalent C-F bonds, (CxF)n, on the MgF2and CaF2added carbon anode surface was accelerated by pre-electrolysis at potentials less than 4.0 V. Critical current densities (CCD) on the MgF2added carbon anodes pre-electrolyzed under various conditions were determined, and the highest CCD was 290 mA cm-2obtained for that pre-electrolyzed at 3.5 V for 500 C cm-2. This anode was successfully used in the electrolysis at 100 mA cm-2for 290 h and the maximum NF3current efficiency was 55%. From these results, it was concluded that the metal fluoride added carbon anode treated by pre-electrolysis has a high potential for electrolytic production of NF3at higher current density. © 2010 Elsevier Ltd., Electrochimica Acta, 564425 - 4432, 30 Apr. 2011, English, Research paper (scientific journal) - Simultaneous measurement of the effective ionic conductivity and effective electronic conductivity in a porous electrode film impregnated with electrolyte
Zyun Siroma, Jumpei Hagiwara, Kazuaki Yasuda, Minoru Inaba, Akimasa Tasaka
A new method for the simultaneous measurement of the effective ionic conductivity and effective electronic conductivity in a porous sheet consisting of an electronic conductor and an ionic conductor (electrolyte) is proposed. In this method, two potentiostats and a voltage source are used, and these instruments are connected to the sample via two terminals made of the electronic conductor and two terminals made of the ionic conductor. The underlying principle of this technique does not include any assumption about charge-transfer resistance at the ionic conductor/electronic conductor interface, since the measurement is designed to let the potential difference at the interface be the OCP value at each point throughout the sample. The validity of this method was confirmed by measuring a pseudo-catalyst layer for a proton-exchange membrane fuel cell (PEMFC). The results revealed that the effective ionic and electronic conductivity depends on the relative humidity. © 2010 Elsevier B.V. All rights reserved., Journal of Electroanalytical Chemistry, 64892 - 97, 01 Oct. 2010, English, Research paper (scientific journal) - Irreversible capacity and lithium-ion insertion/extraction kinetics of a high potential negative electrode TiO
2 (B)
Yosuke Murota, Yasuyuki Oba, Mikihiro Takagi, Takayuki Asao, Morihiro Saito, Akimasa Tasaka, Minoru Inaba
Li+ion insertion/extraction properties of TiO2(B) powder, which was prepared from a K2Ti4O9precursor by ionexchange and dehydration, was investigated as a high-potential negative electrode. The irreversible capacity greatly decreased from 124 mAh g-1to ca. 40 mAh g-1when the lower potential limit was raised from 1.0 V to E ≥ 1.2 V, which indicated that the irreversible capacity mainly originated from surface reactions, such as solvent decomposition, at E ≤ 12 V in the first cycle. In galvanostatic intermittent titration tests, large polarization was observed at the beginning and the end of charging. This clearly indicated that a slow process is involved in the insertion reaction at the beginning and the end of charging, which causes solvent decomposition at potentials lower than 1.4 V. The reversible capacity was greatly improved to 246 and 276 mAh g-1at an elevated temperature of 60°C and at a lower rate of C/60, respectively. The TiO2(B) sample contained ca. 14 wt% of the anatase phase as an impurity, and a reduction of the anatase phase was found to be effective for an increase in reversible capacity at moderate charge/discharge rates., Electrochemistry, 78431 - 434, 01 Jan. 2010, English, Research paper (international conference proceedings) - Durability of electrocatalysts in polymer electrolyte fuel cells
Minoru Inaba
Durability of electrocatalysts in polymer electrolyte fuel cells has been a major critical issue for commercialization of electric vehicles and stationary cogeneration systems. Though various methods mitigation have been proposed and the durability of fuel cell stacks has been greatly improved, further improvement of durability is needed for use in automotive applications. Here degradation phenomena of electrocatalysts for the cathode and the anode in PEFCs are reviewed and the mechanisms for degradation are discussed. ©The Electrochemical Society., ECS Transactions, 25573 - 581, 01 Dec. 2009, English, Research paper (international conference proceedings) - Chemical degradation of perfluorinated sulfonic acid membranes
Minoru Inaba
Chemical degradation of perfluorinated sulfonic acid (PFSA) membranes during operation is a serious problem to be overcome before commercialization of electric vehicles and stationary cogeneration systems based on polymer electrolyte fuel cells. In this chapter, the mechanism for peroxide/radical formation, which works as an active species for membrane degradation, in the cell is comprehensively introduced, including recent findings. Accelerated testing methodology and the chemistry of PFSA membrane degradation are also outlined to improve the durability of PFSA membranes in polymer electrolyte fuel cells. © 2009 Springer New York., Polymer Electrolyte Fuel Cell Durability, 57 - 69, 01 Dec. 2009, English - Polymer electrolyte fuel cell durability
Felix N. Büchi, Thomas J. Schmidt, Minoru Inaba
A major part of the competitiveness gap of polymer electrolyte fuel cell (PEFC) technology in automotive and stationary co-generation applications is due lack of durability. This book analyzes the relevant degradation processes in PEFC on the level of components, cells and stacks, and applications. Prominent authors from the PEFC field describe and analyze in 23 chapters the relevant degradation mechanisms and mitigation strategies. © Springer Science+Business Media, LLC 2009. All rights reserved., Polymer Electrolyte Fuel Cell Durability, 1 - 507, 01 Dec. 2009, English - New iodide-based molten salt systems for high temperature molten salt batteries
Syozo Fujiwara, Fumio Kato, Syouichiro Watanabe, Minoru Inaba, Akimasa Tasaka
Novel multi-component molten salt systems containing iodides, LiF-LiBr-LiI, LiF-NaBr-LiI, and LiF-LiCl-LiBr-LiI, were investigated for use as electrolytes in high temperature molten salt batteries to improve the discharge rate-capability. The iodide-based molten salts showed higher ionic conductivity (∼3 S cm-1at 500 °C) than conventional LiCl-KCl, and had low enough melting points (below 400 °C) that can be used in practical high temperature molten salt batteries. The iodide-based salts showed instability at temperatures higher than 280 °C in dried air. The decomposition mechanism of iodide-based molten salts was discussed, and it was found that elimination of oxygen from the environment is effective to stabilize the iodide-based molten salts at high temperatures. © 2009 Elsevier B.V. All rights reserved., Journal of Power Sources, 1941180 - 1183, 01 Dec. 2009, English, Research paper (scientific journal) - Effects of type of reactor, crystallinity of SiC, and N F
3 gas pressure on etching rate and smoothness of SiC surface using N F3 gas plasma
A. Tasaka, H. Yamada, T. Nonoyama, T. Kanatani, Y. Kotaka, T. Tojo, M. Inaba
Polycrystalline β-SiC and single-crystalline 4H-SiC surfaces were etched by reactive ion etching (RIE) using N F3gas plasma. A smooth surface was obtained on the polycrystalline SiC after RIE at N F3gas pressures of 2 and 10 Pa for 10 min, and neither spikes nor pillars were formed on it. On the other hand, some pillars were formed on the single-crystalline SiC surface by RIE at N F3gas pressures of 2 and 10 Pa. Though the absence of carbon-rich regions and Si O;xon the outermost surface before etching was confirmed by x-ray photoelectron spectroscopy and Raman analysis, x-ray diffraction analysis revealed that graphite crystallites were present in the single-crystalline SiC bulk. It was concluded that the graphite crystallites acted as masks and the pillars grew up from the graphite crystallites in the single crystalline SiC during RIE. © 2009 American Vacuum Society., Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, 271369 - 1376, 16 Nov. 2009, English, Research paper (scientific journal) - Electronic structures of partially fluorinated lithium manganese spinel oxides and their electrochemical properties
Keisuke Matsumoto, Tomokazu Fukutsuka, Toyoki Okumura, Yoshiharu Uchimoto, Koji Amezawa, Minoru Inaba, Akimasa Tasaka
Partially fluorinated lithium manganese spinel oxides (LiMn1.8Li0.1Ni0.1O4-xFx) were prepared by solid-state reaction. Relationship between the electronic structures of LiMn1.8Li0.1Ni0.1O4-xFx and their electrochemical properties were investigated. X-ray absorption near-edge structure (XANES) of Mn K-edge showed that the absorption edge shifted to lower energy with increasing F- content, which indicated decrease of the Mn average oxidation state. Discharge capacity at first cycle was increased by decrease of the Mn average oxidation state with increasing F- content. © 2008 Elsevier B.V. All rights reserved., Journal of Power Sources, 189599 - 601, 01 Apr. 2009, English, Research paper (scientific journal) - Effects of temperature and relative humidity on Oxygen permeation in nation® and sulfonated poly(arylene ether sulfone)
Y. Takamura, E. Nakashima, H. Yamada, A. Tasaka, M. Inaba
Oxygen permeation in Nafion®117 and sulfonated poly(arylene ether sulfone) (BPSH-50) were investigated at different temperatures and relative humidities by a potential step method using a Pt microelectrode. The diffusion coefficient increased, while the solubility decreased with an increased in temperature and relative humidity for both samples. Consequently, the permeability increased with an increased in temperature and relative humidity for both samples. The permeability in BPSH-50 was approximately four times lower than that in Nafion®117, due to a smaller diffusion coefficient and a lower solubility in BPSH-50 than those in Nafion®l 17. Mass transport of oxygen in these membranes was correlated with microstructural changes of the membranes. © The Electrochemical Society., ECS Transactions, 16881 - 889, 01 Dec. 2008, English, Research paper (international conference proceedings) - Electrolysis of (CF3)4NF· 5HF melt with boron-doped diamond anode
Makoto Shizuno, Kenta Nakanishi, Minoru Inaba, Masaharu Uno, Yoshinori Nishiki, Tsuneto Furuta, Akimasa Tasaka
Since a boron-doped diamond (BDD) electrode is able to be used as an anode in the (CH3)4NF·mHF melt, the performance of BDD anode for electrolytic production of perfluorotrimethylamine [(CF 3)3N] was investigated in the melt of (CH 3)4NF·5.0HF by galvanostatic electrolysis at 20, 40, 60 and 100 mA·cnf-2. The anode gas was analyzed quantatively by gas chromatography-mass spectroscopy. Also, the surface of BDD electrode before and after electrolysis was analyzed by XRD and Raman spectroscopy and was observed by SEM. The ratios of (CF3) 3N and (CF3)2CHF2N to overall anode gas increased with increasing the current density. This fact suggests that electrolytic fluorination may be promoted at higher current density. From the results of surface analyses, it is concluded that the electrolytic production of (CF3)3N from (CH3)4NF·5.0HF melt using a BDD anode is an appropriate process because the BDD film on the carbon substrate has a good electric conductivity during electrolysis. ©The Electrochemical Society., ECS Transactions, 161 - 6, 01 Dec. 2008, English, Research paper (international conference proceedings) - Effect of electrolyte composition and anode material on current efficiency for NF
3 formation in electrolytic synthesis using diamond anode
Akira Nishida, Atsushi Kobayashi, Hiroyuki Omori, Minora Inaba, Masaharu Uno, Yoshinori Nishiki, Tsuneto Furatab, Akimasa Tasaka
The current efficiency for NF3 formation was investigated using a Boron-Doped diamond (BDD) anode in the NH4F·mHF melts. The current efficiency for NF3 formation depended on both the current density and the NH4F-concentration in the melt and it trended to decrease at the higher current density. Its maximum value on the BDD anode in a NH4F·2.0HF melt was 72.4% at 40 mA cm-2 and that in a NH4F·1.7HF melt was 46.2% at 100 mA cm-2. Addition of nickel fluoride to the NH4F·mHF melt was effective for increasing the current efficiency for NF3 formation. This is because Ni2+ ion may be oxidized on the BDD anode to form highly oxidized nickel compounds such as NiF3 and/or Ni2F 5 on the anode and NiF63- and/or NiF 62- ions in the melt, which are strong fluorinating agents. The maximum current efficiency for NF3 formation on the BDD anode in a NH4F·2.0HF melt having nickel ion was 61.9% even at the current density of 1000 mA cm-2. ©The Electrochemical Society., ECS Transactions, 16469 - 477, 01 Dec. 2008, English, Research paper (international conference proceedings) - Effect of CsF-concentration on electrolytic conductivity, viscosity and anodic reaction of nickel electrode in (CH3)3N-CsF-HF system at room temperature
Akimasa Tasaka, Akimasa Tasaka, Kenta Nakanishi, Noriaki Masuda, Takaaki Nakai, Kunitaka Momota, Minora Inaba, Minora Inaba
In order to improve the current efficiency for perfluorotrimethylamine, (CF3)3N, formation using Ni anode, mixed melts of (CH 3)3N·mHF + CsF·2.3HF were used as electrolytes at room temperature. The ionic conductivity of the mixed melts decreased with an increase in CsF concentration, whereas the viscosity of the mixed melts increased with increasing CsF concentration. XRD analysis revealed the presence of CsNi2F6 in the oxidized layer formed on the Ni anode after electrolysis. The gas evolved at the Ni anode was composed of (CF 3)3N, (CF3)2CHF2N, CF3(CHF2)2N, (CHF2)3N, CF4, NF3, CHF3, C2HF5, and C2F6. The best ratio of (CF3)3N to the total anode gas (52.11%) was obtained in the electrolyte of (CH 3)3N·5.0HF + 50 wt.% CsF·2.3HF mixed melt at 20 mA cm-2. ©The Electrochemical Society., ECS Transactions, 16517 - 527, 01 Dec. 2008, English, Research paper (international conference proceedings) - Electrochemical AFM study of LiMn
2 O4 thin film electrodes exposed to elevated temperatures
Takayuki Doi, Minoru Inaba, Hiroshi Tsuchiya, Soon Ki Jeong, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
Surface morphology changes of LiMn2O4thin film positive electrodes in lithium-ion batteries after repeated potential cycling or storage at elevated temperatures were observed by in situ atomic force microscopy (AFM) to elucidate the origin of capacity fading of LiMn2O4. After repeated potential cycling in the overall potential range from 3.50 to 4.30 V at elevated temperatures, the entire thin film surface was covered with small round-shaped particles accompanied by capacity fading of the electrode, while no significant changes were observed at 25 °C. The discharge capacity decreased more significantly when cycled in the lower potential range (3.81-4.07 V) than when cycled in the higher potential range (4.04-4.30 V). After storage at elevated temperatures at a depth of discharge (DOD) of 75%, which is located in the lower potential range, similar surface morphology changes were observed. In addition, discharge capacity markedly decreased, and the crystallinity of the LiMn2O4thin film was lowered after storage. Hence, the observed changes in morphology at elevated temperatures are closely related to capacity fading of the LiMn2O4thin film. The loss of crystallinity was caused by the formation of small particles on the LiMn2O4surface, which would be accelerated on the LiMn2O4surface in contact with an electrolyte solution through some kind of dissolution/precipitation reaction. © 2008 Elsevier B.V. All rights reserved., Journal of Power Sources, 180539 - 545, 15 May 2008, English, Research paper (scientific journal) - Stability of Pt-Ru/C catalysts: Effect of Ru content
H. Yamada, D. Shimoda, K. Matsuzawa, K. Matsuzawa, A. Tasaka, M. Inaba
Stability of four kinds of commercially available Pt-Ru/C (Pt:Ru = 1:1 for Samples A1, B1, and C1, and Pt:Ru = 1:2 for Sample B2) anode catalysts was investigated in 0.5 M H2SO4 by potential cycling. When the upper limit was set at potentials higher than 0.4 V, all Pt-Ru(1:1)/C samples were unstable and Ru concentration on the surface decreased during potential cycling tests. The degradation rate increased with increasing the upper potential limit. On the other hand, Samples A1 and B1 showed different tendencies in stability in the potential range of 0.05 to 0.2 V, depending on the crystallinity and the surface state (e.g. the presence of RuOx). Sample B2 (Pt:Ru = 1:2) had a higher stability than Sample B1 (Pt:Ru = 1:1) at high potentials > 0.4 V. On the contrary, the former had an inferior stability in the potential range of 0.05 to 0.2 V. © The Electrochemical Society., ECS Transactions, 11325 - 334, 01 Dec. 2007, English, Research paper (international conference proceedings) - Measurment and thermodynamic analysis of NiF
2 /Ni electrode potential in a dehydrated melt of NH4 F·2HF
Akimasa Tasaka, Eiki Morimoto, Atsuhisa Mimoto, Akitoshi Inoue, Minoro Inaba
A Ni reference electrode was prepared and its potential was also determined in a NH4F·2HF melt at 100°C The value of potential on the Ni electrode was unstable for 30 days. On the other hand, potentials on Ni electrodes treated with anodic oxidation at 10 mA/cm2for 3 days and thermal fluorination with NF3under 1 atm at 300°C for 1 hour became stable after shorter time. The former was 0.075 V and the latter was 0.072 V against hydrogen evolution potential (V vs. H2). The value of potential was almost the same in every measurement. SEM observation and XPS analysis revealed that both pre-treated Ni electrodes were covered with the dense layer composed of NiF2with a small amount of nickel oxide and/or nickel oxyfluoride. The potential of the NiF2/Ni electrode at 100°C calculated from the thermodynamic data is -0.178 V vs. H2. This value of potential was different from the observed one. On the other hand, the potential of the NiO/Ni electrode calculated from thermodynamic data is 0.164 V vs. H2. AS the observed value of potential on the Ni electrode is between both potentials of the NiF2/Ni and the NiO/Ni electrodes, its potential may be determined by nickel oxyfluoride, NiOxFy, in the surface layer of the Ni electrode. Therefore, it is concluded that a Ni electrode covered with the oxidized layer mainly composed of NiF2is useful as a reference electrode for electrochemical measurement and electrolytic production of NF3using a nickel anode. copyright The Electrochemical Society., ECS Transactions, 3529 - 542, 01 Dec. 2007, English, Research paper (international conference proceedings) - Electrochemically constructed p-Cu
2 O/n-ZnO heterojunction diode for photovoltaic device
Masanobu Izaki, Tsutomu Shinagawa, Ko Taro Mizuno, Yuya Ida, Minoru Inaba, Akimasa Tasaka
Polycrystalline n-ZnO/p-Cu2O heterojunctions have been fabricated by low-temperature eletrodepositions of ZnO and Cu2O layers in aqueous solutions. The condition for forming the Cu2O layer significantly reflected the electrical rectification characteristic and the photovoltaic performance, and the heterojunction fabricated under optimized conditions showed an excellent electrical rectification characteristic and a photovoltaic performance of 1.28% in conversion efficiency under an AM 1.5 illumination. © 2007 IOP Publishing Ltd., Journal of Physics D: Applied Physics, 403326 - 3329, 07 Jun. 2007, English, Research paper (scientific journal) - Anodic behavior of each component in a few nickel-metal composites and effect of added metal in composites on electrolytic production of NF
3
Sojiro Kon, Atsuhisa Mimoto, Atsuhisa Mimoto, Tsuyoshi Maeda, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
The nickel-metal composites such as Ni-Co, Ni-Mn, Ni-Ag, and Ni-Si were prepared by Hot Isostatic Pressing (HIP). The ratios of each metal in the mixture were 5 and 10 mol%. These materials were employed as the anode for electrolytic production of NF3. The current efficiencies for NF3formation on the Ni-Co, the Ni-Mn, the Ni-Ag, and the Ni-Si composite anodes were 42-38%, 52-40%, 52-47%, and 41%, respectively, and were small compared with those on the Ni sheet and the HIPed Ni anodes. On the other hand, the current losses caused by anodic dissolution (Qa/Qt) of the Ni-Co, the Ni-Mn, the Ni-Ag, and the Ni-Si composites were 7.95-4.42%, 6.40-7.02%, 5.60-6.30%, and 0.18%, respectively. Those of the Ni-Co, the Ni-Mn, and the Ni-Ag were large compared with those of the Ni anodes, whereas that of the Ni-Si composite was small compared with those of the Ni anodes. Therefore, it is concluded that only Si may prevent effectively the Ni-based composite from anodic dissolution., Proceedings - Electrochemical Society, PV 2004-24528 - 536, 01 Dec. 2006 - Measurement and thermodynamic analysis of reference electrode potentials in a few fluoride melts containing HF
Atsuhisa Mimoto, Atsuhisa Mimoto, Tatsuo Miyazaki, Kazuchika Takao, Jumpei Yamashita, Shingo Nagamine, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
Potential on a copper reference electrode was measured at 100°C in each dehydrated melt of a KF·2HF, a NH4F·KF·4HF, and a NH4F·2HF against hydrogen evolution potential on a Pt rod by voltammetry with a sweep rate of 5 to 10 mV/s. Its value on a fresh copper reference electrode was unstable for first 30 days, whereas those on the anodically oxidized and the thermally fluorinated copper reference electrodes became stable for the shorter time. The stable value of potential on the thermally fluorinated copper reference electrode in a KF·2HF melt was 0.402 ± 0.003 V vs. H2. On the other hand, the theoretical value of potential calculated from thermodynamic data was 0.388 V. It has a little difference from observed value of it, and it may be caused by coexistence of CuF with CuF2 on the surface of a copper reference electrode. Although the theoretical potential on a Ni/NiF2 reference electrode was -0.248 V, the observed potential on a nickel reference electrode in a KF·2HF melt at 100°C was 0.096 ± 0.010 V vs. H2. It was different from the calculated potential of a Ni/NiF2 electrode. From these results, it is concluded that a new type of a copper electrode designated as Cu/CuF2-x (0<x<1) is useful as a reference electrode in the fluoride melts containing HF., Proceedings - Electrochemical Society, PV 2004-24448 - 457, 01 Dec. 2006 - Development of anode for electrolysis of (CH
3 )4 NF-HF room-temperature molten fluoride
Kazuki Onoda, Yoshio Shodai, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
The sol-gel LiNiO2 coated Ni and the sol-gel LaNiO3 coated Ni sheet anodes were developed to improve the Ni sheet anode for electrolytic synthesis of perfluorotrimethylamine, (CF3) 3N, using the (CH3)4NF-4HF melt as the electrolyte. The LiNiO2 and the LaNiO3 films may give the electric conductivity to the Ni sheet anode during electrolysis of the (CH 3)4NF-4HF melt. (CF3)3N was successfully obtained at a ratio of about 25% together with other partially fluorinated gaseous products., Proceedings - Electrochemical Society, PV 2004-24537 - 546, 01 Dec. 2006 - Measurement and thermodynamic analysis of M/MF
n (M = Cu and Fe) electrode potentials in a few fluoride melts containing HF
Atsuhisa Mimoto, Atsuhisa Mimoto, Tatsuo Miyazaki, Jumpei Yamashita, Shingo Nagamine, Minoru Inaba, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka, Akimasa Tasaka
The potentials of copper and iron reference electrodes were measured in dehydrated melts of KF·2HF, NH 4F·KF·4HF, and NH 4F·2HF against the hydrogen evolution potential on Pt. The potential of a fresh copper reference electrode was unstable for the initial 30 days and then became constant, whereas those of an anodically oxidized and a thermally fluorinated copper reference electrode became stable in a shorter time. The potential of the thermally fluorinated copper reference electrode obtained experimentally in the KF·2HF melt was 0.402 ± 0.003 vs H 2 at 373 K, and the values for the three kinds of copper electrodes were close to one another. Theoretical electrode potentials calculated from thermodynamic data were 0.458 V for CuF 2/Cu and 0.307 V for CuF/Cu against HF/H 2. Because the observed potentials on the copper electrodes existed between these values, it may be caused by coexistence of CuF and CuF 2 on the surface. These copper electrodes, which should be denoted as CuF 2 + CuF/Cu or CuF x(1 < x < 2)/Cu, are useful as reference electrodes for electrochemical measurements in fluoride melts containing HF. The observed potentials of the fresh iron and the thermally fluorinated iron electrodes in the KF·2HF melt at 373 K were -0.1.47 ± 0.004 and -0.195 ± 0.003 V vs H 2, respectively, and were not in agreement with each other. Both iron electrodes after immersion in the melt were covered with the film composed of FeF 3 and FeF 2; however, the theoretical potentials [E(FeF 3/Fe) 373 = -0.355 V and E(FeF 2/Fe) 373 = -0.434 V vs E(HF/H 2) 373] were fairly lower than the experimentally observed values. These results suggested that the potential of iron electrodes was determined by other minor species on the surface and therefore, they cannot be used as reference electrodes in fluoride melts containing HF. © 2006 The Electrochemical Society. All rights reserved., Journal of the Electrochemical Society, 153D149 - D154, 24 Oct. 2006, English, Research paper (scientific journal) - Porous metal tubular support for solid oxide fuel cell design
Atsushi Mineshige, Atsushi Mineshige, Koji Fukushima, Sachio Okada, Takeyuki Kikuchi, Masafumi Kobune, Tetsuo Yazawa, Kenji Kikuchi, Minoru Inaba, Minoru Inaba, Zempachi Ogumi, Zempachi Ogumi
A porous nickel tubular support of 1 mm diam was successfully created by heat-treating a commercial nickel tube. The resulting tube contained uniform pores, whose diameters ranged from 0.5 to 2.5 μm, depending on treatment temperature. The porous metal tube obtained is a promising candidate for support materials for microfuel cells or gas separation membranes because it has the necessary gas permeability and mechanical strength. It was also confirmed that a solid oxide fuel cell design employing the porous nickel tube as a supporting anode could be operated. © 2006 The Electrochemical Society., Electrochemical and Solid-State Letters, 9A427 - A429, 03 Aug. 2006, English, Research paper (scientific journal) - Anodic behavior of LiF-impregnated carbon and surface analysis of pristine carbon (FE-5) electrode polarized at various potentials in dehydrated melts of NH
4 F·KF-·mHF (m = 3 and 4)
Akimasa Tasaka, Akimasa Tasaka, Masako Yamanaka, Eiki Morimoto, Shingo Nagamine, Atsuhisa Mimoto, Atsuhisa Mimoto, Tsuyoshi Fujikawa, Masaaki Abe, Atsushi Kobayashi, Hitoshi Takebayashi, Tetsuro Tojo, Minoru Inaba
or electrolytic production of NF3in a dehydrated melt of NH4F·KF·4HF at 100° C, impregnation of LiF into the pores of carbon FE-5 anode enhanced the formation of fluorine-graphite intercalation compounds (GICs) having semi-covalent C-F bonds, (CxF)n, on the surface. The addition of LiF to a NH4F·KF·3HF melt also enhanced the formation of the GICs on a graphite sheet anode, and suppresses the occurrence of the anode effect. The minimum stage number of GICs formed on the graphite sheet anode in the NH4F·KF-3HF melt without LiF decreased in an increase in the charge passed during galvanostatic electrolysis at 10 mA cm-2. However, graphite fluoride, (CF)n, with covalent C-F bonds was formed on the outermost surface after 2500 C cm-2were passed without LiF. On the other hand, the addition of LiF to the melt further enhanced the formation of GICs with low stages (e.g. stage 3), and no graphite fluoride was formed up to 5000 C cm-2. It was found that pre-electrolysis at potentials lower than 3 V is effective for obtaining GICs with semi-covalent bonds. The critical current density after treated by pre-electrolysis of 500 C cm-2at 2.3 V, followed by further 500 C cm-2at 4.0 V, increased to 120 mA cm-2. © J. New. Mat. Electrochem. Systems., Journal of New Materials for Electrochemical Systems, 9297 - 303, 01 Jul. 2006 - Vapor-phase deposition for dense CeO
2 film growth on porous substrates
Atsushi Mineshige, Atsushi Mineshige, Minoru Inaba, Minoru Inaba, Shinji Nakanishi, Shinji Nakanishi, Masafumi Kobune, Tetsuo Yazawa, Kenji Kikuchi, Zempachi Ogumi, Zempachi Ogumi
Pure and Sm-doped CeO2 thin films were deposited on porous substrates by vapor-phase deposition, which is similar to the well-known electrochemical vapor deposition (EVD). By supplying metal chlorides (M Cl3, M; Ce and Sm) vapor and oxygen to a disk-shaped porous substrate from opposite directions, a dense oxide film was grown on the chloride side of the substrate with high homogeneity. The films deposited are suitable for the electrolytes in the ceria-based intermediate temperature solid oxide fuel cells (SOFCs). The growth kinetics of these films was also discussed along with an observed growth rate and theoretical analysis based on oxygen flux and oxygen potential gradient over the film and the substrate. It was found that the film growth was governed by rates of each competitive process: diffusion of oxygen molecules through substrate pores, oxygen reduction (O2 →2 O2-) at the film/substrate interface, and transport of electrochemical species (O2- and e-) through the growing dense film. © 2006 The Electrochemical Society., Journal of the Electrochemical Society, 153A975 - A981, 16 May 2006, English, Research paper (scientific journal) - Preparation of lanthanum nickel oxide-coated Ni sheet anodes and their application to electrolytic production of (CF
3 )3 N in (CH3 )4 NF·4.0HF melt
Yoshio Shodai, Minoru Inaba, Kazuki Onoda, Akimasa Tasaka
A new process for electrolytic production of a perfluorinated compound, (CF3)3N, using lanthanum nickel oxide-coated Ni sheet anode in the (CH3)4NF·4.0HF melt at room temperature, was developed. Thin films of the lanthanum nickel oxides were prepared on Ni sheets by sol-gel coating method using polyvinlylpyrrolidone (PVP). The main components of the thin films were La2O3, LaNiO3, and La2NiO4at 500, 750 and 1000°C, respectively. The anode performance in the (CH3)4NF·4.0HF melt depends greatly on the main component of the thin film, and the LaNiO3-coated Ni sheet anode gives the best anode performance. The potential of LaNiO3-coated Ni sheet anode remains constant at 5.9 V during electrolysis at 20 mA·cm-2in the ((CH3)4NF·4.0HF melt for 100 h. This is because LaNiO3and NiF3and/or Ni2F5, the latter of which was formed during electrolysis, in the film give a high electronic conductivity to the surface film during electrolysis. The maximum mole fraction of (CF3)3N (21.4%) was obtained at 20 mA·cm-2in (CH3)4NF·4.0HF melt using the LaNiO3-coated Ni sheet., Journal of Rare Earths, 241 - 8, 01 Jan. 2006, English, Research paper (scientific journal) - Hydrogen peroxide formation as a degradation factor of polymer electrolyte fuel cells
M. Inaba, H. Yamada, J. Tokunaga, K. Matsuzawa, A. Hatanaka, A. Tasaka
20wt.% Pt/C catalyst was loaded at different densities (0.28-56.7 μgcarboncm-2) on glassy carbon (GC) disk electrode, and the effect of its agglomeration on hydrogen peroxide formation in oxygen reduction reaction (ORR) was investigated by the rotating ring-disk electrode technique. The formation of H2O2was enhanced with a reduction in agglomeration of Pt/C. Even in the operating potential range of PEFC cathodes (0.6-0.8 V), 20% of hydrogen peroxide was formed on Pt/C loaded at densities lower than 1.41 μgcarboncm-2on GC. These results revealed that series 2-electron reduction pathway, which is negligible on clean bulk Pt surface, exists on Pt nanoparticles supported on carbon. A large amount of H2O2formation was observed on Pt nanoparticles deposited not only on GC, but also on Au, which indicated that H2O2formation is not specific to Pt nanoparticles on carbon support. copyright The Electrochemical Society., ECS Transactions, 1315 - 322, 01 Dec. 2005, English, Research paper (international conference proceedings) - Preparation of LiNiO 2-coated Ni sheet anodes and their application to electrolytic production of (CF 3) 3N in (CH 3) 4NF·4.0HF melt
Yoshio Shodai, Akihiro Miyasaka, Kazuki Onoda, Hiroyuki Takei, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
LiNiO 2-coated Ni sheet modes were prepared by a sol-gel coating method and an atmospheric plasma-spraying technique, and were used in electrolytic production of (CF 3) 3N in a room-temperature molten fluoride (CH 3) 4NF·4.0HF. Li xNi 2-xO 2 thin films of x = 0.6-0.8 were successfully formed on Ni sheets by the sol-gel coating methods. The LiNiO 2 film prepared by atmospheric plasma-spraying technique had nearly the stoichiometric composition (x ≈ 1). These LiNiO 2-coated Ni sheet anodes gave lower anode potentials than pure Ni anode during electrolysis, because the presence of the LiNiO 2 layer suppressed the formation of NiF 2 insulation layer and the electronic conductivity of the former was much higher than that of the latter. The maximum mole fraction of (CF 3) 3N of 33% in the anode gas was obtained in electrolysis using the plasma-sprayed LiNiO 2-coated Ni sheet anode at 20 mA cm -2 in the (CH 3) 4NF·4.0HF melt. The anodic potential under the above conditions was 4.13 V after electrolysis for 100 h, which was the lowest of all experiments. Consequently, stoichiometric LiNiO 2-coated Ni sheet was the most preferable anode material for the electrolytic (CF 3) 3N synthesis in the (CH 3) 4NF·4.0HF melt. © 2005 The Electrochemical Society. All rights reserved., Journal of the Electrochemical Society, 152D220 - D226, 01 Dec. 2005, English, Research paper (scientific journal) - Suppression of an alkyl dicarbonate formation in li-ion cells
Takeshi Sasaki, Takeshi Abe, Takeshi Abe, Yasutoshi Iriyama, Yasutoshi Iriyama, Minoru Inaba, Minoru Inaba, Minoru Inaba, Zempachi Ogumi, Zempachi Ogumi
Two methods were developed to suppress the formation of alkyl dicarbonate in Li-ion cells. One is the addition of vinylene carbonate (VC), which is vulnerable to nucleophilic attack, into the electrolyte to trap alkoxide anions that promote an alkyl dicarbonate formation. The addition of VC into the electrolyte of practical graphite/LiCoO2prismatic cells effectively suppressed an alkyl dicarbonate formation and gave better cycle and power performance. The other method is a surface treatment of graphite to reduce the concentration of phenolic groups that were directly bonded to the graphite edge plane. The mild burn-off treatment successfully decreased the oxygen concentration on graphite surface and effectively suppressed an alkyl dicarbonate formation in the electrolyte. However, the irreversible capacity increased significantly, which was considered to be due to a change in the surface morphology of graphite by the burn-off treatment. © 2005 The Electrochemical Society. All rights reserved., Journal of the Electrochemical Society, 152A2046 - A2050, 11 Nov. 2005, English, Research paper (scientific journal) - Effect of an alkyl bicarbonate on Li-ion cell performance
Takeshi Sasaki, Soon Ki Jeong, Takeshi Abe, Takeshi Abe, Yasutoshi Iriyama, Yasutoshi Iriyama, Minoru Inaba, Minoru Inaba, Zempachi Ogumi
The effect of an alkyl dicarbonate, diethyl 2,5-dioxahexane dicarboxylate (DEDOHC, C2H5OCO2C2H4OCO2C2H5), which is formed by an ester exchange reaction in a mix solvent system of ethylene carbonate (EC) and diethyl carbonate (DEC), on the performance of graphite/LiCoO2lithium-ion cells was investigated. In the presence of 10 vol % DEDOHC in 1 M LiClO4/EC + DEC(1:1 v/v), discharge capacity decreased, in particular at a high charge/discharge rate. Capacity retention at a high charge/discharge rate also decreased during repeated charge and discharge cycles. These deteriorations in performance were attributed to an increase in cell impedance and deficiency of mobile lithium ion, which is caused by continuous consumption of lithium ion on graphite negative electrode. The results of half-cell tests revealed that the addition of DEDOHC causes serious degradation for the graphite half-cell. From ac impedance measurements it was found that surface film resistance on graphite electrode was fourfold higher in the solution containing DEDOHC, whereas charge-transfer resistance scarcely changed. Atomic force microscopy observation revealed the formation of dense and highly adhesive surface precipitate layer on graphite electrode in the presence of DEDOHC. Consequently, it was concluded that the increase in cell impedance, which leads to deterioration of charge and discharge performance, is mainly due to the increase in the resistance of the surface film formed from the reduction of DEDOHC on the graphite negative electrode. © 2005 The Electrochemical Society. All rights reserved., Journal of the Electrochemical Society, 152A1963 - A1968, 11 Nov. 2005, English, Research paper (scientific journal) - Electrolytic synthesis of perfluorotrimethylamine with CaF
2 added carbon and original carbon anodes
Akimasa Tasaka, Akimasa Tasaka, Akihiro Miyasaka, Yoshio Shodai, Atsuhisa Mimoto, Atsuhisa Mimoto, Jumpei Yamashita, Tatsuo Miyazaki, Kazuki Onoda, Hitoshi Takebayashl, Tetsuro Tojo, Kunitaka Momota, Minoru Inaba
The new carbon electrodes containing alkali and/or alkali earth metal fluorides such as LiF-CaF2 and CaF2 were developed to prevent the occurrence of anode effect in electrochemical fluorination and were used as the anode for electrolytic synthesis of perfluorotrimethylamine, (CF3)3N, from mixed melt of (CH3) 4NF·5HF and KF·2HF at 100°C. The ratio of (CF 3)3N to the overall anode gas increased with increasing the concentration of (CH3)4NF and decreasing the current density, and the best value of 61.7% was obtained in electrolysis of the mixed melt of (CH3)4NF·5HF (40 mol %) and KF-2HF (60 mol%) at 20 mA cm-2 with the 4 wt% CaF2 added carbon anode. Also, the best value of its ratio in electrolysis at the same current density with the ordinary carbon anode (FE-5) was obtained in the mixed melt of (CH3)4NF-5HF (30 mol%) and KF-2HF (70 mol%) and was 81.4%. XPS analysis revealed that the surface of anode after electrolysis was mainly covered with the layer of the C-F intercalation compounds having the semi-covalent and ionic bonds. However, the new carbon anode was broken down in the mixed melt of (CH3)4NF·5HF (50 mol%) and KF-2HF (50 mol%) during electrolysis at 40 mA cm-2. From these results, it is concluded that the alkali and/or alkali earth metal fluoride added carbons as well as the carbon (FE-5) is available as the anode for electrolytic production of (CF3)3N from the mixed melt having the molar fraction of KF higher than 0.143., Electrochemistry, 73661 - 667, 01 Aug. 2005 - Anodic behavior of nickel-based alloys in the electrolytic production of NF
3
Atsuhisa Mimoto, Atsuhisa Mimoto, Sojiro Kon, Tsuyoshi Maeda, Takuya Motomura, Kengo Nishimura, Minoru Inaba, Akimasa Tasaka, Akimasa Tasaka
The Ni-based alloys, such as Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si, prepared by hot isostatic pressing (HIP) at 1000°C under 2 × 108Pa for 2 h were employed as the anodes for electrolytic production of NF3. The current efficiencies for NF3formation were 42-38, 52-40, 52-47, 63-62, 50 and 41% for Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si alloys, respectively. The current efficiencies only on Ni-Cu alloys with Cu concentrations lower than 10 mol% were almost the same as those on Ni sheet and HIPed Ni anodes, whereas those on the other alloys used in this study were smaller compared with those on both Ni anodes. On the other hand, the current losses caused by anodic dissolution of Ni-Co, Ni-Mn, Ni-Ag, Ni-Cu, Ni-Al and Ni-Si alloy electrodes were 7.95-4.42, 6.40-7.02, 5.60-6.30, 3.34-6.33, 5.10 and 0.18%, respectively. The anode consumptions of Ni-5 mol% Cu and Ni-5 mol% Si alloys were almost the same or smaller compared with those of Ni sheet and HIPed Ni electrodes, though those of other alloys used were large compared with those of both Ni anodes. Consequently, addition of Cu to the nickel matrix is available for a cheaper cost of anode with keeping a same current efficiency as that on the Ni anode and addition of Si to the nickel matrix is effective for decreasing anode consumption largely. A Ni sheet electrode containing a trace of impurities, such as Co, Mn, Ag and Al, is also favorable as the anode for electrolytic production of NF3., Journal of Fluorine Chemistry, 1261101 - 1110, 01 Jul. 2005, English, Research paper (scientific journal) - Structural and electrical characterizations of electrodeposited p-type semiconductor Cu
2 O films
Kotaro Mizuno, Masanobu Izaki, Kuniaki Murase, Tsutomu Shinagawa, Masaya Chigane, Minora Inaba, Akimasa Tasaka, Yasuhiro Awakura
The p-type semiconductor cuprous oxide (Cu2O) film has been of considerable interest as a component of solar cells and photodiodes due to its bandgap energy of 2.1 eV and high optical absorption coefficient. We prepared Cu2O films on a conductive substrate by electrodeposition at 318 K from an aqueous solution containing copper sulfate and lactic acid. The structural and electrical characterizations of the resulting films were examined by X-ray diffraction. X-ray photoelectron spectroscopy, and X-ray absorption measurements, and the Hall effect measurement, respectively. The resistivity varied from 2.7 × 104 to 3.3 × 106 Ω cm, while the carrier density was from 1012 to 1014 cm -3 and the mobility from 0.4 to 1.8 cm2 V-1 s-1, depending on the preparation conditions, i.e., solution pH and deposition potential. The carrier density was sensitive to the atomic ratio of Cu to O in the films and the mobility to the grain size. © 2005 The Electrochemical Society. All rights reserved., Journal of the Electrochemical Society, 152C179 - C182, 20 May 2005, English, Research paper (scientific journal) - Hydrogen peroxide formation as a degradation factor of polymer electrolyte fuel cells
Minoru Inaba, Hirohisa Yamada, Junko Tokunaga, Masayuki Kiriake, Akimasa Tasaka, Taro Kinumoto, Zempachi Ogumi
Durability is one of the most important issues in commercialization of PEFCs. Hydrogen peroxide formation, which is formed electrochemically or chemically during operation, is one of the potential deteriorating factors of PEFCs. We have focused on hydrogen peroxide as a degradation factor of PEFC stacks, and have investigated durability of the electrolyte membrane used in MEAs against hydrogen peroxide and the mechanism for hydrogen peroxide formation at Pt/C catalysts. We have also studied the degradation of MEAs by operating a single cell under accelerated operating conditions. In this report, recent results on these topics are summarized., Proceedings - Electrochemical Society, PV 2004-21370 - 379, 01 Dec. 2004 - AFM study on SEI growth on graphite negative electrode at elevated temperatures
Minoru Inaba, Hanako Tomiyasu, Akimasa Tasaka, Soon Ki Jeong, Zempachi Ogumi
Morphology changes of the surface of highly oriented pyrolytic graphite (HOPG) electrode during cycling and storage at elevated temperatures were observed by in situ AFM to envisage the SEI growth and its stability. AFM observation of the SEI layer revealed that two important facts on the stability of the SEI at elevated temperatures: (i) dissolution and agglomeration of the SEI layer at the discharged state, and (ii) serious SEI growth at the charged state. These phenomena well explained the results of the charge and discharge tests. It was also shown that the addition of vinylene carbonate greatly improves the stability of the SEI at an elevated temperature., Proceedings - Electrochemical Society, PV 2003-2811 - 19, 01 Dec. 2004 - Preparation of LiFePO
4 thin films by pulsed laser deposition and their electrochemical properties
Yasutoshi Iriyama, Misuzu Yokoyama, Chihiro Yada, Soon Ki Jeong, Soon Ki Jeong, Izumi Yamada, Takeshi Abe, Minoru Inaba, Zempachi Ogumi
Olivine structured LiFePO4thin films were prepared by pulsed laser deposition and their electrochemical properties were investigated by cyclic voltammetry (CV) and charge-discharge tests. The resultant films exhibited only a couple of anodic and cathodic peaks at ∼3.4 V, which is characteristic of olivine LiFePO4, on CV between 2.0 and 5.0 V (vs. Li/Li+). The discharge capacity estimated from the CV obtained at 100 mVs-1maintained 69% of that obtained at 1 mVs-1. This high rate capability is probably due to the film being so thin that the intrinsically poor electronic conductivity of LiFePO4was not of importance. © 2004 The Electrochemical Society. All rights reserved., Electrochemical and Solid-State Letters, 7A340 - A342, 22 Nov. 2004, English, Research paper (scientific journal) - Electrolysis of mixed melt of (CH3)4NF· mHF + x wt.% CsF·2.0HF with nickel anode
Yoshio Shodai, Minoru Inaba, Kunitaka Momota, Tomotaka Kimura, Akimasa Tasaka
A new process for electrolytic synthesis of a perfluorinated compound using mixed melts of (CH3)4NF·4.0HF + xwt.% CsF·2.0HF as electrolytes and Ni sheet anode at room temperature was developed. The addition of CsF·2.0HF reduced the overvoltage of the Ni anode. The surface film on the anode formed in the presence of CsF·2.0HF consisted of inorganic compounds of NiF2, CsNi2F6, and an organic compound of (CH3)4NF. The presence of CsNi2F6, which is a highly oxidized nickel compound, gave a high electronic conductivity to the film and decreased the anode overvoltage. The gas evolved on the anode was composed of (CF3)3N and CF4as main products with small amounts of NF3, C2F6, CHF3, C2HF5, CF3N(CF2H)2, and (CF3)2NCHF2. The addition of 20wt.% CsF·2.0HF gave the highest ratio of (CF3)3N of 40.5% when the electrolysis was carried out at 5mAcm-2at room temperature. © 2004 Elsevier Ltd. All rights reserved., Electrochimica Acta, 492131 - 2137, 30 May 2004, English, Research paper (scientific journal) - Anionic species (FH)
x F-in room-temperature molten fluorides (CH3 )4 NF·mHF
Yoshio Shodai, Shinji Kohara, Yasuo Ohishi, Minoru Inaba, Akimasa Tasaka
Ionic and nonionic species in (CH3)4NF·mHF melts (m = 3.0-5.0) were investigated by1H NMR, IR spectroscopy, Raman spectroscopy, and high-energy X-ray diffraction measurements. Three types of anions, (FH)F-, (FH)2F-, and (FH)3F-, were identified in these melts. The(FH)2F-anion was thermodynamically the most stable of the complex anions in the (CH3)4NF·mHF (3.0 ≤ m ≤ 5.0), and its concentration was the highest. (FH)xF-anions with x = 4 and 5 were not present at room temperature though the presence of (FH)xF-(x = 1-5) has been known in the solid-state crystals. In the (CH3)4NF·mHF melts with m = 3.0 - 5.0, the number of HF combined with F-is three or less, and excess HF exists as molecular HF., Journal of Physical Chemistry A, 1081127 - 1132, 19 Feb. 2004, English, Research paper (scientific journal) - Atomic Force Microscopy Study on the Stability of a Surface Film Formed on a Graphite Negative Electrode at Elevated Temperatures
Minoru Inaba, Hanako Tomiyasu, Akimasa Tasaka, Soon Ki Jeong, Soon Ki Jeong, Zempachi Ogumi
The stability at elevated temperatures of a solid electrolyte interphase (SEI) formed on a graphite negative electrode in lithium ion batteries was investigated by storage tests and in situ atomic force microscopy (AFM) observation. When the fully discharged graphite electrode was stored at elevated temperatures, the irreversible capacity in the following cycle increased remarkably. On the other hand, when the electrode was stored at the fully charged state at elevated temperatures, it was severely selfdischarged during storage. AFM observation of the SEI layer formed on a model electrode of highly oriented pyrolytic graphite revealed two important facts on the stability of the SEI at elevated temperatures: (i) dissolution and agglomeration of the SEI layer at the discharged state and (ii) serious SEI growth at the charged state. These phenomena well explain the results of the charge and discharge tests. It was also shown that the addition of vinylene carbonate greatly improves the stability of the SEI at elevated temperatures, and gives good charge and discharge performance after storage., Langmuir, 201348 - 1355, 17 Feb. 2004, English, Research paper (scientific journal) - Proton conductivity of (NH
4 )2 TiP4 O13 -based material for intermediate temperature fuel cells
Toshiaki Matsui, Shinya Takeshita, Yasutoshi Iriyama, Takeshi Abe, Minoru Inaba, Zempachi Ogumi
A new proton-conductive electrolyte of (NH4)2TiP4O13was synthesized for intermediate temperature fuel cells. Structure of the resultant electrolyte was studied by X-ray diffraction and its ionic conductivities was obtained from AC impedance spectroscopy. Partial decomposition of (NH4)2TiP4O13occurred by annealing at 300°C under a dry argon atmosphere, resulting in the formation of TiP2O7, and after annealing its proton conductivity was evaluated to be about 5 mS cm-1at 300°C under the same dry argon atmosphere. Electrolyte of (NH4)2SiP4O13was prepared for comparison. In contrast to (NH4)2TiP4O13, it is stable under a dry Ar atmosphere at 300°C, and its proton conductivity was 0.6 mS cm-1. These results indicate that partial decomposition of (NH4)2TiP4O13to TiP2O7should be responsible for high proton conductivity. © 2003 Elsevier B.V. All rights reserved., Electrochemistry Communications, 6180 - 182, 01 Jan. 2004, English, Research paper (scientific journal) - AFM study of surface film formation on a composite graphite electrode in lithium-ion batteries
Soon Ki Jeong, Soon Ki Jeong, Minoru Inaba, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
An in situ electrochemical atomic force microscopy (AFM) observation of a composite graphite electrode surface was performed in 1 mol dm-3LiClO4dissolved in a mixture of ethylene carbonate (EC)+diethyl carbonate (DEC), and propylene carbonate (PC) to show the applicability of scanning probe microscopy (SPM) to studies using composite graphite electrodes. In EC + DEC, three kinds of morphological changes (curling, swelling, and exfoliation) in the vicinity of the particle edges were observed in the potential range of 0.8-1.4 V versus Li+/Li. These morphological changes were caused by the intercalation of solvated lithium ions and their subsequent decomposition between graphene layers. On the other hand, vigorous exfoliation and rupturing of graphene layers of the graphite particles were observed at 0.9 V in PC. In addition, deterioration by the formation of holes in the composite graphite electrode was observed in PC, which is attributable to gas evolution upon decomposition of PC molecules. © 2003 Elsevier Science B.V. All rights reserved., Journal of Power Sources, 119-121555 - 560, 01 Jun. 2003, English, Research paper (international conference proceedings) - Correlation between cointercalation of solvents and electrochemical intercalation of lithium into graphite in propylene carbonate solution
Takeshi Abe, Naoki Kawabata, Yasuo Mizutani, Minoru Inaba, Zempachi Ogumi
Correlation of solvent cointercalation and electrochemical intercalation of Li into graphite was studied. Cointercalation of dimethylsulfoxide (DMSO), 2-methyltetrahydrofuran (2-MeTHF), dimethoxymethane (DMM), diethoxymethane (DEM), 1,2-diethoxyethane (DEE) and 1,2-dibutoxyethane (DBE) into graphite with Li was investigated by the solution method to find out that DMSO, DMM, DEM, and DEE can cointercalate into graphite with Li and that 2-MeTHF and DBE cannot. By using the functional density theory, steric hindrance of solvated lithium ion was found to be predominant for cointercalation. Electrochemical Li intercalation into graphite was studied in propylene carbonate (PC) solution containing 1 mol dm-3 LiClO4 in the presence of various amounts of the above solvents. By the addition of DMSO in the PC electrolyte, solvent decomposition at around 1.0 V (vs. Li/Li+) was thoroughly suppressed, and electrochemical intercalation of Li took place. Suppression of the solvent decomposition was dependent on the amount of DMSO. This is because competing cointercalation of DMSO suppressed the cointercalation of PC which causes the exfoliation of graphite, leading to the formation of the stable solid electrolyte interface. Suppression of cointercalation of PC was also observed by the addition of DMM, DEM, and DEE in a limited condition. Addition of 2-MeTHF and DBE into the PC electrolyte is not available for electrochemical intercalation of lithium. These results show that cointercalation plays an important role for electrochemical intercalation of lithium into graphite., Journal of the Electrochemical Society, 150A257 - A261, 01 Mar. 2003, English, Research paper (scientific journal) - Study of the decomposition of propylene carbonate on lithium metal surface by pyrolysis - Gas chromatography - Mass spectroscopy
Ryo Mogi, Ryo Mogi, Minoru Inaba, Minoru Inaba, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
The compositions of surface films formed on lithium metal in different propylene carbonate (PC)-based solutions and the decomposition processes in the surface film formation were investigated by pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS). It was found that the main component in the surface film formed in 1 mol dm-3(M) LiClO4/PC has a chemical structure of ROCH(CH3)CH2OR′, of which -OR and -OR′ can be -OLi or -OCO2Li. A general scheme for reactions that took place on the lithium electrode in 1 M LiClO4/PC and in the pyrolyzer was elucidated from the results by Py-GC-MS analysis. In 1 M LiClO4/PC containing 5 wt% fluoroethylene carbonate (FEC) as an additive, FEC was dominantly reduced to form an active species, Li+-OCO2̇, which further reacted with a PC molecule to form the same main component, ROCH(CH3)CH2OR′. This mechanism suggested that the same active species also might be formed from PC even in the absence of FEC. Another possible route was suggested, in which decomposition of PC is initiated by a nucleophilic attack of an alkoxide. The chemical composition of surface film was greatly affected by the kind of lithium salts. Decomposition products of lithium bis(perfluoroethylsulfonyl)-imide (LiBETI) were detected from the surface film formed in 1 M LiBETI/PC. In contrast, the surface film formed in 1 M LiPF6/PC consisted mainly of inorganic compounds with a much smaller amount of organic compounds., Langmuir, 19814 - 821, 04 Feb. 2003, English, Research paper (scientific journal) - Electrochemical intercalation of lithium ion within graphite from propylene carbonate solutions
Soon Ki Jeong, Soon Ki Jeong, Minoru Inaba, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
Electrochemical lithium intercalation within graphite was investigated in propylene carbonate (PC) containing different concentrations, 0.82 and 2.72 mol dm-3, of bis(perfluoroethylsulfonyl)imide, LiN(SO2C2F5)2. Lithium ion was reversibly intercalated into and deintercalated from graphite in the latter concentrated solution in spite of the use of pure PC as a solvent, whereas ceaseless solvent decomposition and intensive exfoliation of graphene layers occurred in the former solution. X-ray diffraction analysis revealed that a stage I graphite intercalation compound was formed after being fully charged in the 2.72 mol dm-3 solution. The results of Raman analysis indicated that no free PC molecules are present in the concentrated solution, which suggested that the ion/solvent interactions would be an important factor that determines the ability of stable surface film formation in PC-based solutions., Electrochemical and Solid-State Letters, 6A13 - A15, 01 Jan. 2003, English, Research paper (scientific journal) - Surface modification of carbonaceous thin films by NF
3 plasma and their effects on electrochemical properties
Tomokazu Fukutsuka, Yoshiaki Matsuo, Yosohiro Sugie, Takeshi Abe, Minoru Inaba, Zempachi Ogumi
Carbonaceous thin films were prepared by plasma-assisted chemical vapor deposition. Surface of resultant films were treated by NF3plasma at room temperature. From Roman spectra, crystallinity of sample remained almost unchanged by the surface treatment. The reduction current at 0.6V vs. Li/Li+in the cyclic voltammograms at the 1st cycle decreased with increasing the flow rate of NF3. This result indicates that fluorine atoms bonded to carbon atoms play an important role in decreasing the side reaction at the 1st reduction process., Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals, 388[531]/117 - [536]/122, 01 Dec. 2002, English, Research paper (international conference proceedings) - Plasma etching of SiC surface using NF
3
A. Tasaka, K. Takahashi, K. Tanaka, K. Shimizu, K. Mori, S. Tada, W. Shimizu, T. Abe, M. Inaba, Z. Ogumi, T. Tojo
The RIE process for the βSiC was developed and it had a high etching rate of 87 nm/min. However, it was restricted by the conditions such as rf power of 100 W and NF3pressure ranging from 0.5 to 1 Pa. The surface of the SiC has many spikes under other conditions. The repetitive alternating treatment for the surface of SiC with DFE using NF3and Ar plasma sputtering enabled to obtain the smooth surface without Si3N4formation on it., Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, 201254 - 1260, 01 Jul. 2002, English, Research paper (scientific journal) - Surface film formation on a graphite negative electrode in lithium-ion batteries: AFM study on the effects of co-solvents in ethylene carbonate-based solutions
Soon Ki Jeong, Minoru Inaba, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
In situ AFM observation of the basal plane of highly oriented pyrolytic graphite (HOPG) was performed before and after cyclic voltammetry in 1 mol dm-3LiClO4dissolved in ethylene carbonate (EC), EC+diethyl carbonate (DEC), and EC+dimethyl carbonate (DMC) to clarify the effects of co-solvents in EC-based solutions on surface film formation on graphite negative electrodes in lithium-ion cells. In each solution, surface film formation involved the following two different processes: (i) intercalation of solvated lithium ions and their decomposition beneath the surface; and (ii) direct decomposition of solvent molecules on the basal plane to form a precipitate layer. The most remarkable difference among these solvent systems was that solvent co-intercalation took place more extensively in EC+DEC than in EC+DMC or EC. Raman analysis of ion-solvent interactions revealed that a lithium ion is solvated by three EC molecules and one DEC molecule in EC+DEC, whereas it is solvated exclusively by EC in EC+DMC and in EC, which suggested that the presence of linear alkyl carbonates in the solvation shell of lithium ion enhance the degree of solvent co-intercalation that occurs in the initial stage of the surface film formation. © 2002 Elsevier Science Ltd. All rights reserved., Electrochimica Acta, 471975 - 1982, 07 May 2002, English, Research paper (scientific journal) - Creation of nanospaces by intercalation of alkali metals into graphite in organic solutions
Y. Mizutani, T. Abe, M. Inaba, Z. Ogumi
Co-intercalation of alkali metals (Li, Na, K, Rb and Cs) with various organic solvents has been utilized for introducing nanospaces in graphite. The co-intercalation has been conducted by a solution method. Resultant products were studied by X-ray diffraction. For solvents of cyclic ethers, co-intercalation is likely to occur for heavy alkali metals of Rb and Cs. For linear ethers with one oxygen atom, binary graphite intercalation compounds (GICs) were mainly obtained, irrespective of alkali metal species. For linear ethers with two oxygen atoms, light alkali metal, in particular, Li tends to give ternary Li-solvent-GICs. From these results, it is concluded that co-intercalation is mainly influenced by the interaction between alkali metals and solvents and by the size of solvated alkali metals. © 2001 Elsevier Science B.V. All rights reserved., Synthetic Metals, 125153 - 159, 01 Jan. 2002, English, Research paper (scientific journal) - Surface Film Formation on Graphite Negative Electrode in Lithium-Ion Batteries: AFM Study in an Ethylene Carbonate-Based Solution
Soon Ki Jeong, Minoru Inaba, Takeshi Abe, Zempachi Ogumi
In situ atomic force microscopic (AFM) observation of the basal plane of highly oriented pyrolytic graphite was performed during cyclic voltammetry at a slow scan rate of 0.5 mV s-1 in 1 mol dm-3 LiClO4 dissolved in a mixture of ethylene carbonate and diethyl carbonate. In the potential range 1.0-0.8 V, atomically flat areas of 1 or 2 nm height (hill-like structures) and large swellings of 15-20 nm height (blisters) appeared on the surface. These two features were formed by the intercalation of solvated lithium ions and their decomposition beneath the surface, respectively, and may have a role in suppressing further solvent cointercalation. At potentials more negative than 0.65 V, particle-like precipitates appeared on the basal plane surface. After the first cycle, the thickness of the precipitate layer was 40 nm, and increased to 70 nm after the second cycle. The precipitates were considered to be mainly organic compounds that are formed by the decomposition of solvent molecules, and they have an important role in suppressing further solvent decomposition on the basal plane. © 2001 The Electrochemical Society. [DOI: 10.1149/1.1387981] All rights reserved., Journal of the Electrochemical Society, 148A989 - A993, 01 Sep. 2001, English, Research paper (scientific journal) - Effects of the molecular structure of fluorinated additives on the kinetics of cathodic oxygen reduction
Jun Maruyama, Minoru Inaba, Tohru Morita, Zempachi Ogumi
The kinetics of oxygen reduction at a gold electrode was studied in 0.5 M sulfuric acid, in which different kinds of straight-chain [CF3(CF2)2CH2OH, CF3CF2CH2OH, and CF3CH2OH] and branched [(CF3)2CHOH] fluorinated alcohols were added. The adsorbed layers of the fluorinated alcohols were used as models of the fluorocarbon phase of the perfluorinated polymer electrolyte in gas-diffusion electrodes in proton-exchange membrane fuel cells. A rotating ring-disk electrode was used to determine kinetic parameters for O2reduction and to detect intermediate H2O2formation. The kinetics of oxygen reduction were strongly dependent on the molecular structure of fluorinated additives. The addition of the straight-chain fluorinated alcohols enhanced the kinetic current density while addition of the branched alcohol did not. The linear C3fluorinated alcohol, CF3CF2CH2OH, gave the maximum enhancement effect. Oxygen is reduced predominantly via the two-electron series path in the range of 0.4 to 0.0 V at Au, on which no effect of fluorinated additives was observed. The rate constant for intermediate H2O2reduction, k3, was negligible in the range 0.40-0.25 V, whereas it increased with decreasing EDin the range 0.25-0.0 V. In the lower potential range, k3decreased with an increase in the concentration of fluorinated alcohol and this decreasing tendency was greatly dependent on the molecular structure of the fluorinated alcohol. © 2001 Elsevier Science B.V., Journal of Electroanalytical Chemistry, 504208 - 216, 18 May 2001, English, Research paper (scientific journal) - Structure and electrochemical behaviors of Li
x CoO2 (x > 1) treated under high oxygen pressure
N. Imanishi, M. Fujii, A. Hirano, Y. Takeda, M. Inaba, Z. Ogumi
The electrochemical behavior of LixCoO2(x > 1.0) and its high pressure oxygen-treated samples were examined as cathode of lithium ion battery. LixCoO2was prepared at nominal compositions of Li/Co = 1.02, 1.05, 1.10, 1.15, 1.20, 1.25, and 1.30. The practical compositions and cobalt valences were analyzed by ICP and iodometric titration technique. X-ray diffraction patterns show that the lattice gradually contracts with increasing Li/Co ratio. The lattice contraction stops at Li/Co = 1.15, which corresponds to the solid solution limit. The high oxygen pressure treatment reduced the number of oxygen defects and enlarged the interlayer distance. The electrochemical behavior of oxygen-treated samples show better cycling efficiency and less irreversible capacities. The reversible capacities show clear dependence on Li/Co ratio that the highest capacity of 140 mA h g-1was obtained when Li/Co = 1.10 and beyond that value it decreased linearly with Li/Co ratio. © 2001 Elsevier Science B.V., Solid State Ionics, 14045 - 53, 01 Mar. 2001, English, Research paper (scientific journal) - Preparation of c-axis oriented thin films of LiCoO
2 by pulsed laser deposition and their electrochemical properties
Yasutoshi Iriyama, Minoru Inaba, Takeshi Abe, Zempachi Ogumi
Thin films of LiCoO2with a preferred c-axis orientation were prepared by pulsed laser deposition. Thin films deposited for 1-2 h had a preferred c-axis orientation, but films deposited for 3 h and longer lost the preferred orientation. The textures of these films were investigated in detail by transmission electron microscopy and selected area electron diffraction. The electrochemical properties of these films were compared by cyclic voltammetry and alternating current impedance spectroscopy. In the cyclic voltammograms of the c-axis oriented films, the anodic and cathodic peaks corresponding to the first-order phase transition at around 3.9 V were sharp and their peak separation was small due to their thin and uniform texture. However, their smooth surface and texture of the aligned (0 0 3) planes gave a larger charge-transfer resistance and a smaller apparent diffusion coefficient in the direction normal to the substrate, respectively, which resulted in poor utilizations (approximately 50%) of the active material. The reactivity in the single-phase region at potentials more positive than 4.0 V was lower than that of randomly oriented films., Journal of Power Sources, 94175 - 182, 01 Mar. 2001, English, Research paper (scientific journal) - Pyrolysis/gas chromatography/mass spectroscopy analysis of the surface film formed on graphite negative electrode
Zempachi Ogumi, Atsushi Sano, Minoru Inaba, Takeshi Abe
The chemical constituents of the protective surface film formed on graphite negative electrode in ethylene carbonate (EC)-based electrolyte solutions were analyzed by pyrolysis/gas chromatography/mass spectroscopy (Pyro/GC/MS). Oligomers that consist of oxyethylene units, such as ethylene glycol, di(ethylene glycol), and tri(ethylene glycol) methyl ester, were detected. These oligomers were formed by reductive decomposition of EC, and their presence suggested that the surface film contained polymer-like substances that have repeated oxyethylene units. © 2001 Elsevier Science B.V., Journal of Power Sources, 97156 - 158, 01 Jan. 2001, English, Research paper (scientific journal) - High capacity technology of nickel-metal hydride batteries
Zempachi Ogumi, Soon Ki Jeong, Minoru Inaba, Takeshi Abe
The nickel-Metal hydride battery has been recognized as an important power source for various cordless appliances since its commercialization in 1990. Therefore, demands for capabilities of the batteries have been increasing. A key technology to meet these demands is improvement of the electrode materials. This work is focused on improving composition and microstructure of the bulk and surface states of hydrogen-absorbing alloys used as the negative electrode material and the composition of the nickel hydroxide and additives used for the positive electrode., Macromolecular Symposia, 156203 - 211, 21 Dec. 2000 - Transmission electron microscopy (TEM) analysis of two-phase reaction in electrochemical lithium insertion within α-MoO
3
Yasutoshi Iriyama, Takeshi Abe, Minoru Inaba, Zempachi Ogumi
The mechanism of a phase transition in electrochemical lithium insertion into α-MoO3was investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). α-MoO3was deposited on a special Au micro grid for TEM observation by pulsed laser ablation. The phase transition ranged from x = 0 to 0.25 in LixMoO3upon electrochemical lithium insertion into α-MoO3. In this two-phase coexistence region, the XRD (020) line of the lithium inserted phase (Li0.25MoO3) grew at the expense of the (020) line of the pristine α-MoO3as lithium ions were inserted. However, the intensity of the lithium-inserted phase was much weaker than expected in the initial stage of the phase transition. TEM observation revealed that lithium ions were inserted randomly into some preferred crystallites of α-MoO3to form a disordered phase in the initial stage, which explained the presence of the induction period upon the growth of the lithium inserted phase., Solid State Ionics, 13595 - 100, 01 Nov. 2000, English, Research paper (scientific journal) - Electrical Property, Crystal Structure and Oxygen Nonstoichiometry of La
1-x Srx Co0.2 Fe0.8 O3-δ
Atsushi Mineshige, Junko Izutsu, Maiko Nakamura, Kengo Nigaki, Masafumi Kobune, Satoshi Fujii, Minoru Inaba, Zempachi Ogumi, Takeshi Yao
Electrical conductivity of mixed conducting perovskite-type oxide, La1-xSrxCo0.2Fe0.8O 3-δ (LSCF, 0.4≤x≤0.7) was determined as functions of Sr-content (x), temperature (T) and oxygen partial pressure [P(O2)]. Crystal structure and oxygen nonstoichiometry (δ) of LSCF was evaluated and correlated with its electrical property. The electrical conductivity (σ) in LSCF was greatly affected by oxygen nonstoichiometry and B-O-B angle (B; B-site elements) in the crystal., Electrochemistry, 68515 - 518, 01 Jun. 2000 - STM Study of Well-Defined Graphite/Electrolyte Interface Polarized in Propylene Carbonate Solution Containing 12-Crown-4
Minoru Inaba, Yutaka Kawatate, Atsushi Funabiki, Soon Ki Jeong, Takeshi Abe, Zempachi Ogumi
Surface morphology change of highly oriented pyrolytic graphite was investigated in 1 M (M = mol dm-3) LiClO4 dissolved in propylene carbonate (PC) and PC - 0.5 M 12-crown-4 using electrochemical scanning tunneling microscopy to elucidate the mechanism of passive film formation on graphite electrode in rechargeable lithium batteries. In PC, vigorous exfoliation of graphite layers was observed after potential cycling down to 0 V vs. Li/Li+. Such exfoliation was greatly suppressed by 12-crown-4 addition. The original step structure was nearly maintained, but swellings of graphite surface appeared after potential cycling. From these results, the role of 12-crown-4 in passive film formation was discussed., Electrochemistry, 671153 - 1155, 01 Dec. 1999 - Metal-Insulator Transition and Crystal Structure of La
1-x Srx CoO3 as Functions of Sr-Content, Temperature, and Oxygen Partial Pressure
Atsushi Mineshige, Masafumi Kobune, Satoshi Fujii, Zempachi Ogumi, Minoru Inaba, Takeshi Yao, Kenji Kikuchi
Electrical properties of La1-xSrxCoO3(LSC) change with variations in Sr content, temperature, and oxygen partial pressure. With a change in each variable, LSC showed metal-insulator transition (MIT). The changes in electrical properties of LSC were correlated here with those of its crystal structure. The variations of crystallographic parameters such as the length ofa-axis, the rhombohedral angle, the Co-O distance, and the Co-O-Co angle (θ) were precisely determined by powder X-ray Rietveld analysis. Of these, the variation ofθdescribed most consistently the variation of conduction state, metallic or insulating, of LSC. The Co-O-Co angle increased whenever the conduction state changed from insulating to metallic by changing each variable, Sr content, temperature, and oxygen partial pressure. In addition, MIT took place at a critical Co-O-Co angle of ca. 165° in each case. It was concluded that the transition from insulator to metal is caused by the closing of the charge transfer band gap, induced by broadening of the electronic bandwidths of the Co-3dand O-2pbands with an expansion of the Co-O-Co angle. © 1999 Academic Press., Journal of Solid State Chemistry, 142374 - 381, 01 Feb. 1999, English, Research paper (scientific journal) - Influence of defects on the phase-boundary movement in a stage transformation of lithium-graphite intercalation compounds
Atsushi Funabiki, Minoru Inaba, Takeshi Abe, Zempachi Ogumi
The influence of defects on the phase-boundary movement in the stage transformation from random stage (dilute stage 1) to stage 4 of lithium-graphite intercalation compounds was investigated using highly oriented pyrolytic graphite (HOPG). Potential-step chronoamperometry and in situ optical microscopy coupled with micro Raman spectroscopy were used to clarify macroscopic and microscopic influence of defects. Potential-step chronoamperometry confirmed that the diffusion-limited rate of the phase-boundary movement in the bulk of HOPG was independent of the crystallinity of the samples. This result indicates that defects have macroscopically no appreciable influence on the phase-boundary movement. In situ optical microscopy on the basal plane of HOPG revealed that the nucleation and growth of the stage-4 phase took place quite inhomogeneously in the initial stage. The rate of the phase-boundary movement in the surface region of HOPG was roughly evaluated to be in the range of 5 to 10 μm min-1. The phase-boundary movement was seriously retarded by cracks formed on the basal plane during the stage transformation., Carbon, 371591 - 1598, 01 Jan. 1999, English, Research paper (scientific journal) - Electrochemical STM observation of LiMn
2 O4 thin films prepared by pulsed laser deposition
Minoru Inaba, Takayuki Doi, Yasutoshi Iriyama, Takeshi Abe, Zempachi Ogumi
Spinel LiMn2O4thin films were prepared by pulsed laser deposition. The surface morphology change of the film with potential cycling between 3.5 and 4.25 V was observed in 1 M LiClO4/PC by electrochemical scanning tunneling microscopy. After cycling, small round-shaped particles of 120-250 nm in diameter appeared on the surface. The number of the newly formed particles increased with repeated cycling while the size decreased. The observed morphology change suggested that the small particle were formed from the solution through a kind of dissolution/precipitation reactions. © 1999 Elsevier Science S.A. All rights reserved., Journal of Power Sources, 81-82554 - 557, 01 Jan. 1999, English, Research paper (scientific journal) - In situ raman and STM techniques for studies on rechargeable lithium batteries
Minoru Inaba, Zempachi Ogumi
Electrochemistry, 66986 - 991, 01 Dec. 1998 - In situ Raman and STM techniques for studies on rechargeable lithium batteries
Minoru Inaba, Zempachi Ogumi
Denki Kagaku, 66986 - 991, 01 Dec. 1998 - Rotating ring-disk electrode study on the cathodic oxygen reduction at Nafion®-coated gold electrodes
Jun Maruyama, Minoru Inaba, Zempachi Ogumi
The influence of Nafion® films on the kinetics of cathodic oxygen reduction was investigated using Nafion®-coated gold electrodes. A rotating ring-disk electrode (RRDE) technique was used to determine kinetic parameters for O2reduction and to detect intermediate H2O2formation. Kinetic parameters such as the kinetic current, Tafel slope, potential dependence of the ratio of the direct 4-electron reduction to the series 2-electron reduction were determined and compared with those obtained at bare Au in 0.5 M H2SO4. The kinetic data showed no clear evidence of the enhancement effects of Nafion®-coating on the cathodic O2reduction at Au. This suggested that the Au surface has less affinity for the hydrophobic region of Nafion®, in which a high O2solubility is expected. © 1998 Elsevier Science S.A. All rights reserved., Journal of Electroanalytical Chemistry, 458175 - 182, 30 Oct. 1998, English, Research paper (scientific journal) - Influence of Nafion® film on the kinetics of anodic hydrogen oxidation
Jun Maruyama, Minoru Inaba, Katsumi Katakura, Zempachi Ogumi, Zen Ichiro Takehara
The influence of Nafion® film on the kinetics of anodic oxidation of hydrogen was investigated on Nafion®-coated platinum electrodes. Hydrodynamic voltammetry was used to obtain the kinetic current for the H2oxidation reaction, and the exchange current densities at bare and Nafion®-coated Pt rotating disk electrodes were determined using the modified Koutecky-Levich equations. The exchange current density at Nafion®-coated Pt was higher by 20% than that at bare Pt in 0.1 M HClO4. The enhancement in exchange current density was attributed to a higher H2solubility in recast Nafion® than in the solution. The hydrogen solubility in recast Nafion® determined by potential step chronoamperometry (PSCA) was 1.4 × 10-6mol cm-3, which was 1.8 times higher than that in the solution (0.78 × 10-6mol cm-3). The difference in H2solubility determined by potential step chronoamperometry was larger than that estimated from the difference in exchange current density. The discrepancy was explained by the peculiar multiphase-structure of Nafion®, where H2solubility in the electrochemically inactive fluorocarbon region is higher than that in the ionic cluster region. © 1998 Elsevier Science S.A. All rights reserved., Journal of Electroanalytical Chemistry, 447201 - 209, 30 Apr. 1998, English, Research paper (scientific journal) - Impedance study on the electrochemical lithium intercalation into natural graphite powder
Atsushi Funabiki, Minoru Inaba, Zempachi Ogumi, Shin Ichi Yuasa, Junhiko Otsuji, Akimasa Tasaka
Electrochemical lithium intercalation into natural graphite powder of different sizes was studied by alternating current impedance spectroscopy. Impedance spectra at various potentials were fitted with a modified Randles equivalent circuit including a pseudocapacitance to express the observed finite diffusional behavior. The variations of electrochemical parameters with electrode potential, such as the charge-transfer resistance, the pseudocapacitance, the Warburg prefactor, and, finally, the chemical diffusion coefficient of lithium ion within graphite, were evaluated and discussed. It was shown that the charge-transfer reaction takes place on the whole surface of graphite particles, whereas lithium ion is intercalated from the edge plane and diffuses to the interior. The kinetics of the charge-transfer reaction was independent of the structure of the host. In contrast, the diffusivity of lithium ion within graphite was strongly dependent on the host structure, and the dependence was explained in terms of differences in in-plane and stacking order of lithium-graphite intercalation compounds formed by the intercalation., Journal of the Electrochemical Society, 145172 - 178, 01 Jan. 1998, English, Research paper (scientific journal) - Growth rate of yttria-stabilized zirconia thin films formed by electrochemical vapour-deposition using NiO as an oxygen source: II. Effect of the porosity of NiO substrate
Minoru Inaba, Atsushi Mineshige, Tomoyuki Maeda, Shinji Nakanishi, Tsutomu Ioroi, Tadayoshi Takahashi, Akimasa Tasaka, Kenji Kikuchi, Zempachi Ogumi
Yttria-stabilized zirconia (YSZ) thin films were formed at 1000°C by a modified electrochemical vapour-deposition (EVD) using NiO as an oxygen source, and ZrCl4and YCl3as metal sources. Growth rate kinetics were examined using NiO pellet substrates with different pore structures. The thickness of YSZ film increased linearly with deposition time, and the growth rate increased with increasing the porosity of the substrate. The pore size as well as the porosity affected the growth rate. In addition, the observed growth rate was much slower than the theoretical one assuming that the electrochemical transportation of the charged species across the growing film is rate limiting. From these results, it was concluded that the rate-determining step is not the bulk electrochemical transport, but the mass transport of dissociated oxygen in the substrate pore., Solid State Ionics, 104303 - 310, 11 Dec. 1997 - Graphite intercalation compounds prepared in solutions of alkali metals in 2-methyltetrahydrofuran and 2, 5-dimethyltetrahydrofuran
Y. Mizutani, T. Abe, K. Ikeda, E. Ihara, M. Asano, T. Harada, M. Inaba, Z. Ogumi
The intercalation of alkali metals (Li, K, Rb and Cs) into natural graphite flakes in the solutions of 2-methyltetrahydrofuran (MeTHF) and 2, 5-dimethyltetrahydrofuran (diMeTHF) containing naphthalene has been studied by X-ray diffraction (XRD), where naphthalene is used as a dissolving agent for alkali metals. When MeTHF is used as a solvent, binary Li-and K-graphite intercalation compounds (GICs) have been obtained, in contrast to the case of Rb and Cs, where both binary alkali metal GICs and ternary alkali metal-MeTHF-GICs are obtained. Using diMeTHF instead of MeTHF, a selective preparation of binary GICs for all the alkali metals has been established. Copyright © 1997 Elsevier Science Ltd., Carbon, 3561 - 65, 01 Jan. 1997, English, Research paper (scientific journal) - Raman study of layered rock-salt LiCoO
2 and its electrochemical lithium deintercalation
Minoru Inaba, Yasutoshi Iriyama, Zempachi Ogumi, Yasufumi Todzuka, Akimasa Tasaka
Unpolarized and polarized Raman spectra (200-800 cm-1) of LiCoO2with a layered rock-salt structure were measured. The Raman-active lattice modes of LiCoO2were assigned by polarized Raman measurements of a c-axis oriented thin film. The variation of the Raman spectra of Li1-xCoO2powder prepared by electrochemical lithium deintercalation was investigated, and the spectral changes were well correlated with the structural changes determined by x-ray diffraction except that peak splitting by the distortion in the monoclinic phase was not observed. The observed line broadening of the second hexagonal phase and the monoclinic phase indicated that the lithium ions remaining in the lattice after deintercalation randomly occupy the available sites on the lithium planes in the lattice the layered rock-salt structure. © 1997 John Wiley & Sons, Ltd., Journal of Raman Spectroscopy, 28613 - 617, 01 Jan. 1997, English, Research paper (scientific journal) - Hydrogen oxidation on partially immersed Nafion®-coated electrodes
Minoru Inaba, Masaharu Uno, Jun Maruyama, Akimasa Tasaka, Katsumi Katakura, Zempachi Ogumi
The mass transport of hydrogen on partially immersed Nafion®-coated electrodes (Nafion®|Pt|highly oriented pyrolytic graphite) was investigated as a model of the three-phase region of the gas-diffusion electrodes in proton-exchange membrane fuel cells. On raising the electrode from a position at which the Nafion® coating was fully immersed in the electrolyte solution (h = 0mm), the dependence of the H2oxidation current on h was similar to that reported for a partially immersed flat platinum electrode. In contrast, on raising from a partially immersed position (h = 3mm), the current was independent of h, and higher than that when raising from h = 0mm at a given Nafion® thickness. When raising from h = 3 mm, the Nafion® coating above the intrinsic meniscus was not covered with a thin liquid electrolyte film, but functioned solely as a supermeniscus. This made hydrogen diffusion easier, resulting in the observed higher current. From the above results, useful implications for the design of gas-diffusion electrodes in PEMFCs are demonstrated., Journal of Electroanalytical Chemistry, 417105 - 111, 07 Nov. 1996, English, Research paper (scientific journal) - Crystal structure and metal-insulator transition of La
1-x Srx CoO3
Atsushi Mineshige, Minoru Inaba, Takeshi Yao, Zempachi Ogumi, Kenji Kikuchi, Masaya Kawase
Crystal structure of perovskite La1-xSrxCoO3(0.0 ≤ x ≤ 0.7) was precisely determined by powder X-ray Rietveld analysis, and its correlation with the electrical properties was discussed. The space group was assigned to rhombohedral R3̄c in the range 0.0 ≤ x ≤ 0.5 and to cubic Pm3m in the range 0.55 ≤ x ≤ 0.7. At x ∼ 0.25 the Co-O distance and Co-O-Co angle of this system showed an abrupt decrease and increase with increasing x, respectively, and the conductivity behavior changed from semiconducting to metallic. The abrupt changes in crystal structure were attributed to a change in the band structure at the transition from semiconducting to metallic, that is, an increase in the overlap between the valence band and doped hole sates. © 1996 Academic Press, Inc., Journal of Solid State Chemistry, 121423 - 429, 01 Feb. 1996, English, Research paper (scientific journal) - Preparation of functionally gradient fluorocarbon polymer films by plasma polymerization of NF
3 and propylene
Akimasa Tasaka, Akiko Komura, Yoshiharu Uchimoto, Minoru Inaba, Zempachi Ogumi
Fluorocarbon polymer films were prepared by plasma polymerization using nitrogen trifluoride (NF3) and propylene as starting materials. To improve their adhesiveness to substrates, a novel functionally gradient film in which the content of fluorine decreased continuously from the surface to the interior was prepared by changing source gas composition during deposition. This film had a smooth and pinhole-free surface, and had a high contact angle (110°) for water drop. In addition, it showed good adhesion to a glass substrate. © 1996 John Wiley & Sons, Inc., Journal of Polymer Science, Part A: Polymer Chemistry, 34193 - 198, 30 Jan. 1996, English, Research paper (scientific journal) - X-ray diffraction and Raman scattering studies of FeCl
3 -SbCl5 -graphite bi-intercalation compounds
Takeshi Abe, Yasukazu Yokota, Yasuo Mizutani, Mitsuru Asano, Toshio Harada, Minoru Inaba, Zempachi Ogumi
X-ray diffraction (XRD) and Raman spectroscopy have been used for the study of the bi-intercalation of SbCl5into a stage 5 FeCl3-graphite intercalation compound (GIC). The stage 5 FeCl3-GIC is prepared by an ordinary two-bulb method with the temperature of graphite at 788 K and that of FeCl3at 573 K. The FeCl3-SbCl5-graphite bi-intercalation compound (GBC) with one SbCl5layer is obtained when the temperature of the stage 5 FeCl3-GIC is held at 443 K and the temperature of SbCl5at 373 K in the two-zone system. The stacking sequence of the GBC is found to be an admixture of G(FeCl3)GG(SbCl5)GGG(FeCl3)G and G(FeCl3)GGG(SbCl5)GG(FeCl3)G by XRD, where G, (FeCl3), and (SbCl5) are the graphite, FeCl3, and SbCl5layers, respectively. The Raman spectrum of the GBC shows two peaks associated with the E(2)i2gand E(2)b2gmodes at 1588 cm-1and 1610 cm-1, respectively. For the temperatures of stage 5 FeCl3-GIC at 443 K and SbCl5at 403 K in the two-zone system, the FeCl3-SbCl5-GBC with two SbCl5layers is obtained. The stacking sequence of the GBC is determined to be an admixture of G(FeCl3)GG(SbCl5)GG(SbCl5)G(FeCl3)G and G(FeCl3)G(SbCl5)GG(SbCl5)GG(FeCl3)G. In the Raman spectrum of this GBC, two peaks associated with the E(2)b2gmode are observed at 1616 and 1624 cm-1., Journal of Materials Research, 113039 - 3044, 01 Jan. 1996, English, Research paper (scientific journal) - In situ roman study of electrochemical lithium insertion into mesocarbon microbeads heat-treated at various temperatures
Minoru Inaba, Hiroyuki Yoshida, Zempachi Ogumi, Zempachi Ogumi
In situ Raman spectra were measured to elucidate the electrochemical lithium insertion mechanism of mesocarbon microbeads (MCMBs) heat-treated at 700 to 2800°C. The spectral changes of the Raman E2g2band of MCMBs heat-treated at 2800°C showed that the lithium insertion mechanism into the microbeads is similar to that into graphite via the formation of staged graphite intercalation compounds, although a clear phase transition from dilute stage 1 to stage 4 was not observed. For MCMBs heat-treated at 1800 and 1000°C the E2g2band shifted downward and upward upon charging and discharging, respectively. No discontinuous change suggesting the formation of staged phases was observed, which indicated that lithium is inserted randomly between graphene layers without the formation of staged phases. The charge and discharge profile of MCMBs heat-treated at 700°C showed a large hysteresis. A potential plateau appeared at about 1 V on the discharge curve, which led to a high capacity of 710 mAh/g. In the case of MCMBs heat-treated at 700°C, the peak wave number of the E2g2band did not shift at all in the whole potential range during charging and discharging. It was considered that the plateau region of MCMBs heat-treated at 700°C giving the high discharge capacity originates not from lithium species inserted between organized graphene layers, but from lithium doped into regions without organized graphitic structure., Journal of the Electrochemical Society, 1432572 - 2578, 01 Jan. 1996, English, Research paper (scientific journal) - Raman spectroscopic analysis of electrochemical behavior of propylviologen in Nafion
Minoru Inaba, Yumi Osa, Zempachi Ogumi
The electrochemical and Raman spectroscopic characteristics of propylviologen incorporated into Nafion® film coated on a silver electrode were studied. The results were compared with those on silver in solutions containing Triton X-100, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) micelles. Propylviologen incorporated into Nafion® showed unusual electrochemical and Raman spectroscopic behavior. The half-wave potential for the second step was shifted in the negative direction with respect to that in an aqueous solution, and only a small amount of the doubly reduced form was detected by Raman spectroscopy. Similar behavior was observed in the anionic SDS micellar solution. On the basis of the observed similarity, the residence sites of propylviologen in Nafion® were discussed. © 1995., Journal of Electroanalytical Chemistry, 38391 - 98, 21 Feb. 1995, English, Research paper (scientific journal) - Debye-Waller factors of FeCl
3 - and ICl-graphite intercalation compounds
Takeshi Abe, Yasuo Mizutani, Naoki Shinoda, Eiji Ihara, Mitsuru Asano, Toshio Harada, Minoru Inaba, Zempachi Ogumi
Stage 2 and 3 FeCl3-graphite intercalation compounds (GICs) and stage 1-3 ICl-GICs are prepared by a two-bulb method. The stage structures of the GICs are studied by X-ray diffraction, and the GICs are characterized by the full width at half maximum of the (00l) diffraction peaks. The effective Debye-Waller (DW) factors of the well crystallized FeCl3-GICs and ICl-GICs along the c-axis are determined from the structure parameters, with which the minimum crystallographic R factor is obtained. The effective DW factors are found to decrease with increasing the stage number of the FeCl3-GICs and ICl-GICs. The DW factors of the constituent atoms, carbon, iron, and chlorine, in the FeCl3-GICs and those of carbon, iodine, and chlorine in the ICl-GICs are also determined. © 1995., Carbon, 331789 - 1793, 01 Jan. 1995, English, Research paper (scientific journal) - Application of the Solid Polymer Electrolyte Method to Organic Electrochemistry XV. Influence of the Multiphase Structure of Nafion on Electroreduction of Substituted Aromatic Nitro Compounds on Cu, Pt-Nafion
Minoru Inaba, James T. Hinatsu, Zempachi Ogumi, Zen Ichiro Takehara
The influence of Nafion® and its multiphase structure on reactant selectivity in the electroreduction of aromatic nitro compounds on a solid polymer electrolyte composite electrode was investigated. Equimolar solutions of p -nitrotoluene and p-nitrophenol and equimolar solutions of o- and p -nitrotoluene were subjected to electroreduction on Cu, Pt-Nafion. The reactant selectivities, that is, the relative ease with which the reactants are reduced to the corresponding amino compounds, were compared with those on a conventional Cu electrode. Para -nitrotoluene was electroreduced preferentially in both equimolar solutions tested. Enhanced selectivity was observed with Cu, Pt-Nafion relative to the Cu electrode. The enhanced selectivity with Cu, Pt-Nafion was explained in terms of hydrophilic/hydrophobic interactions between the reactants and Nafion, which has a multiphase structure consisting of the polytetrafluoroethylene backbone, ionic clusters, and an interfacial region hydrophobic amorphous region). © 1993, The Electrochemical Society, Inc. All rights reserved., Journal of the Electrochemical Society, 140706 - 711, 01 Jan. 1993, English, Research paper (scientific journal) - Oxygen permeation through perfluorinated carboxylate ion exchange membranes
Minoru Inaba, Minoru Inaba, Tohru Kuroe, Tohru Kuroe, Zempachi Ogumi, Zempachi Ogumi, Zen Ichiro Takehara, Zen Ichiro Takehara, Katsumi Katakura, Katsumi Katakura, Sachio Ichikawa, Sachio Ichikawa, Yoshifumi Yamamoto, Yoshifumi Yamamoto
Permeation of oxygen through perfluorinated carboxylate membranes (Flemion®) of different counterions and equivalent weights (EW = 700 and 800) was investigated. Solubilities and diffusion coefficients of oxygen in the membranes were determined by an electrochemical monitoring technique using solid polymer electrolyte composite electrodes. The solubilities were close to the values in perfluorocarbon media rather than to the value in water. The solubility decreased with increasing water content of the membranes. The diffusion coefficient in 700 EW membranes increased with increasing water content, while that in 800 EW membranes decreased slightly. On the basis of these results, the diffusion path of oxygen through the membranes was discussed in terms of morphological properties of perfluorinated ion exchange membranes. © 1993., Electrochimica Acta, 381727 - 1731, 01 Jan. 1993, English, Research paper (scientific journal) - Application of the Solid Polymer Electrolyte Method to Organic Electrochemistry: XIV. Effects of Solvents on the Electroreduction of Nitrobenzene on Cu, Pt-Nafion
Minoru Inaba, Zempachi Ogumi, Zen ichiro Takehara
The effects of solvents on the electroreduction of nitrobenzene on Cu, Pt-Nafion were investigated. The presence of a sufficient amount of a cosolvent in the catholyte or in the anolyte facilitated the reduction of nitrobenzene to aniline. Without a sufficient amount of a cosolvent, the mass transfer of nitrobenzene to the active sites on the cathode was suppressed, and hydrogen evolution became significant. The solubility parameter value, δmix, of the catholyte is an important index for predicting the effectiveness of mass transfer of nitrobenzene to the active sites of the solid polymer electrolyte composite electrode. When an aqueous solution was used as the anolyte, catholytes with δmix >11 cal-1/2 cm-3/2 were effective for aniline production by the electroreduction of nitrobenzene on Cu, Pt-Nafion. © 1993, The Electrochemical Society, Inc. All rights reserved., Journal of the Electrochemical Society, 14019 - 22, 01 Jan. 1993, English, Research paper (scientific journal) - Infrared sensing properties of positive temperature coefficient thermistors with large temperature coefficients of resistivity
Minoru Inaba, Masaru Miyayama, Hiroaki Yanagida
Infrared (IR) detecting elements were prepared using positive temperature coefficient (PTC) thermistors with large temperature coefficients of resistivity (α). Their compositions were denoted as Ba1-xSrxNb0.003Ti0.997O3+ 1 mol % TiO2+ 0.07 mol %MnO (x=0, 0.2), and their temperature coefficients of resistivity were 78 and 50% K-1, respectively. Their IR sensing properties were measured under the self-regulating heating conditions, and were compared with those of a detector with small α (18 % K-1). It was shown that large α was effective for controlling the element temperature by self-regulating heating and for improving sensitivity. The responsivity, Rvof the element with x=0.2 was 980 VW-1, and was as large as those of pyroelectric detectors. Expressions which normalize the sensitivity and the thermal time constant were derived. From these expressions, criteria for improving some IR sensing properties were obtained. © 1992 Chapman & Hall., Journal of Materials Science, 27127 - 132, 01 Jan. 1992, English, Research paper (scientific journal) - Infrared sensing properties of positive temperature coefficient thermistors with large temperature coefficients of resistivity
Minoru Inaba, Masaru Miyayama, Hiroaki Yanagida
Infrared (IR) detecting elements were prepared using positive temperature coefficient (PTC) thermistors with large temperature coefficients of resistivity (α). Their compositions were denoted as Ba1-xSrxNb0.003Ti0.997O3+ 1 mol % TiO2+ 0.07 mol %MnO (x=0, 0.2), and their temperature coefficients of resistivity were 78 and 50% K-1, respectively. Their IR sensing properties were measured under the self-regulating heating conditions, and were compared with those of a detector with small α (18 % K-1). It was shown that large α was effective for controlling the element temperature by self-regulating heating and for improving sensitivity. The responsivity, Rvof the element with x=0.2 was 980 VW-1, and was as large as those of pyroelectric detectors. Expressions which normalize the sensitivity and the thermal time constant were derived. From these expressions, criteria for improving some IR sensing properties were obtained. © 1992 Chapman & Hall., Journal of Materials Science, 27127 - 132, 01 Jan. 1992, English, Research paper (scientific journal) - Infrared sensing properties of BaTiO
3 PTC thermistor
Minoru Inaba, Masaru Miyayama, Hiroaki Yanagida
Properties of an infrared (IR) detector using a positive temperature coefficient (PTC) thermistor, Ba0.997La0.003TiO3+ 2 mol% SiO2+ 0.07 mol% MnO, operated under the self-regulating heating conditions were investigated. The temperature coefficient of resistance was 18% K-1, and the Curie point was 122°C. It was shown that a PTC thermistor can detect IR radiation from a 600 K blackbody furnace under the self-regulating conditions. However, the response and the thermal time constant were greatly affected by the variation in the ambient temperatures (15°-124°C) and the applied voltage(1-100 V). Theoretical expressions for the response and the thermal time constant were discussed, and the calculated results were consistent with the experimental ones., Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan, 971250 - 1255, 01 Dec. 1989 - Application of the SPE method to organic electrochemistry-VII. The reduction of nitrobenzene on a modified Pt-nafion
Zempachi Ogumi, Minoru Inaba, Shin ichi Ohashi, Masaaki Uchida, Zen ichiro Takehara
SPE composite electrodes prepared by deposition of platinum on Nafion, Pt-Nafions, were modified by electrochemical deposition of nickel and copper. The modified electrodes were applied to the reduction of nitrobenzene. The modification was very effective for aniline formation and suppressed side reactions such as hydrogen evolution. On Cu, Pt-Nafion the Bamberger's rearrangement was inhibited and no p-aminophenol was obtained. The inhibition was caused by Nafion which coated the active site on Cu, Pt-Nafion. It was suggested that SPE composite electrodes behaved in the same manner as polymer coated electrodes. The active site for charge transfer reaction was concluded to be at an interior surface of the metal layer bound to Nafion. © 1988., Electrochimica Acta, 33365 - 369, 01 Jan. 1988, English, Research paper (scientific journal) - Smoothing single-crystalline SiC surfaces by reactive ion etching using pure NF<inf>3</inf> and NF<inf>3</inf>/Ar mixture gas plasmas
Tasaka, A., Kotaka, Y., Oda, A., Saito, M., Tojo, T., Inaba, M.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, 32, 2014, English, Research paper (scientific journal) - Development of anode for electrolysis of (CH
3 )4 NF-HF room-temperature molten fluoride
Onoda, K., Shodai, Y., Inaba, M., Tasaka, A.
Proceedings - Electrochemical Society, PV 2004-24537 - 546, 2006, English, Research paper (international conference proceedings) - Measurement and thermodynamic analysis of reference electrode potentials in a few fluoride melts containing HF
Mimoto, A., Miyazaki, T., Takao, K., Yamashita, J., Nagamine, S., Inaba, M., Tasaka, A.
Proceedings - Electrochemical Society, PV 2004-24448 - 457, 2006, English, Research paper (international conference proceedings) - Anodic behavior of each component in a few nickel-metal composites and effect of added metal in composites on electrolytic production of NF
3
Kon, S., Mimoto, A., Maeda, T., Inaba, M., Tasaka, A.
Proceedings - Electrochemical Society, PV 2004-24528 - 536, 2006, English, Research paper (international conference proceedings) - Anodic behavior of LiF-impregnated carbon and surface analysis of pristine carbon (FE-5) electrode polarized at various potentials in dehydrated melts of NH
4 F?KF-?mHF (m = 3 and 4)
Tasaka, A., Yamanaka, M., Morimoto, E., Nagamine, S., Mimoto, A., Fujikawa, T., Abe, M., Kobayashi, A., Takebayashi, H., Tojo, T., Inaba, M.
Journal of New Materials for Electrochemical Systems, 9297 - 303, 2006, English, Research paper (scientific journal) - Electrolytic synthesis of perfluorotrimethylamine with CaF
2 added carbon and original carbon anodes
Tasaka, A., Miyasaka, A., Shodai, Y., Mimoto, A., Yamashita, J., Miyazaki, T., Onoda, K., Takebayashl, H., Tojo, T., Momota, K., Inaba, M.
Electrochemistry, 73661 - 667, 2005, English - Effect of agglomeration of Pt/C catalyst on hydrogen peroxide formation
Yamada, H., Tokonaga, J., Inaba, M., Tasaka, A.
Proceedings - Electrochemical Society, PV 2004-21235 - 240, 2004, English, Research paper (international conference proceedings) - AFM study on SEI growth on graphite negative electrode at elevated temperatures
Inaba, M., Tomiyasu, H., Tasaka, A., Jeong, S.-K., Ogumi, Z.
Proceedings - Electrochemical Society, PV 2003-2811 - 19, 2004, English, Research paper (international conference proceedings) - Hydrogen peroxide formation as a degradation factor of polymer electrolyte fuel cells
Inaba, M., Yamada, H., Tokunaga, J., Kiriake, M., Tasaka, A., Kinumoto, T., Ogumi, Z.
Proceedings - Electrochemical Society, PV 2004-21370 - 379, 2004, English, Research paper (international conference proceedings) - Surface Film Formation on Graphite Negative Electrode at Elevated Temperatures
Inaba, M., Tomiyasu, H., Tasaka, A., Jeong, S.-K., Iriyama, Y., Abe, T., Ogumi, Z.
Electrochemistry, 711132 - 1135, 2003, English, Research paper (scientific journal) - Preliminary study on direct alcohol fuel cells employing anion exchange membrane
Ogumi, Z., Matsuoka, K., Chiba, S., Matsuoka, M., Iriyama, Y., Takeshi, A.B.E., Inaba, M.
Electrochemistry, 70980 - 983, 2002, English, Research paper (scientific journal) - Surface reactions of carbon negative electrodes of rechargeable lithium batteries
Ogumi, Z., Inaba, M., Abe, T., Jeong, S.-K.
Studies in Surface Science and Catalysis, 132929 - 934, 2001, English, Research paper (international conference proceedings) - High capacity technology of nickel-metal hydride batteries
Ogumi, Z., Jeong, S.-K., Inaba, M., Abe, T.
Macromolecular Symposia, 156203 - 211, 2000, English, Research paper (international conference proceedings) - Electrical Property, Crystal Structure and Oxygen Nonstoichiometry of La
1-x Srx Co0.2 Fe0.8 O3-δ
Mineshige, A., Izutsu, J., Nakamura, M., Nigaki, K., Kobune, M., Fujii, S., Inaba, M., Ogumi, Z., Yao, T.
Electrochemistry, 68515 - 518, 2000, English, Research paper (scientific journal) - STM Study of Well-Defined Graphite/Electrolyte Interface Polarized in Propylene Carbonate Solution Containing 12-Crown-4
Inaba, M., Kawatate, Y., Funabiki, A., Jeong, S.-K., Abe, T., Ogumi, Z.
Electrochemistry, 671153 - 1155, 1999, English, Research paper (scientific journal) - Lithium ion diffusion through glassy carbon plate
Inaba, M., Nohmi, S., Funabiki, A., Abe, T., Ogumi, Z.
Materials Research Society Symposium - Proceedings, 496493 - 498, 1998, English, Research paper (international conference proceedings) - In situ raman and STM techniques for studies on rechargeable lithium batteries
Inaba, M., Ogumi, Z.
Electrochemistry, 66986 - 991, 1998, English, Research paper (scientific journal) - Exploratory studies of the carbon/nonaqueous electrolyte interface by electrochemical and in situ ellipsometry measurements
Kong, F., Kim, J., Song, X., Inaba, M., Kinoshita, K., McLarnon, F.
Electrochemical and Solid-State Letters, 139 - 41, 1998, English, Research paper (scientific journal) - Microelectrode simulation of anode in polymer electrolyte fuel cells
Katakura, K., Hinatsu, J.T., Inatomi, K., Inaba, M., Ogumi, Z., Takehara, Z.-I.
Denki Kagaku, 64711 - 717, 1996, English, Research paper (scientific journal) - Growth rate of yttria-stabilized zirconia thin films formed by electrochemical vapor-deposition using NiO as an oxygen source
Inaba, M., Mineshige, A., Maeda, T., Nakanishi, S., Takahashi, T., Tasaka, A., Kikuchi, K., Ogumi, Z.
Solid State Ionics, 93187 - 192, 1997, English, Research paper (scientific journal) - Growth rate of yttria-stabilized zirconia thin films formed by electrochemical vapour-deposition using NiO as an oxygen source: II. Effect of the porosity of NiO substrate
Inaba, M., Mineshige, A., Maeda, T., Nakanishi, S., Ioroi, T., Takahashi, T., Tasaka, A., Kikuchi, K., Ogumi, Z.
Solid State Ionics, 104303 - 310, 1997, English, Research paper (scientific journal) - Electrochemical scanning tunneling microscopy observation of highly oriented pyrolytic graphite surface reactions in an ethylene carbonate-based electrolyte solution
Inaba, M., Siroma, Z., Funabiki, A., Ogumi, Z., Abe, T., Mizutani, Y., Asano, M.
Langmuir, 121535 - 1540, 1996, English, Research paper (scientific journal) - Infrared sensing properties of a low curie point PTC thermistor
Inaba, Minoru, Miyayama, Masaru, Yanagida, Hiroaki
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan, 98296 - 299, 1990, English, Research paper (scientific journal) - Infrared sensing properties of BaTiO
3 PTC thermistor
Inaba, Minoru, Miyayama, Masaru, Yanagida, Hiroaki
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan, 971250 - 1255, 1989, English, Research paper (scientific journal)
Books etc
- Not entered
The Latest Technologies of The New Secondary Battery Technology, 1997 - Electrolyte Salts
2001 - Carbon Anodes for Lithium-Ion Batteries
Advances in Lithium-Ion Batteries, 2002 - Fuel Cell Characterization Methods
Kagaku Dojin, 2005 - Degradation Mechanisms and Problems in Polymer Electrolyte Fuel Cells
Advanced Technologies for Ubiquitous Energy, Eds. T. Sakai and T. Kobayashi, CMC, 2006 - Degradation Factors in PEFCs: From Electrochemistry
The 46th Elctrochemistry Seminar, The Kansai Branch, The Electrochem. Soc., Japan, 2006 - Electromotive Forces in Batteries
The 36th Electrochemistry Lectures, The Kansai Branch, The Electrochem. Soc., Japan, 2006 - Degradation and Diagnoses of PEFC Cell Stacks
Improvements of Performance and Reliability of Battery Materials, 2007 - Durability of Electrocatalysts in Polymer Electrolyte Fuel Cells
ECS Trans., 2009 - Chemical Degradation of Perfluorinated Sulfonic Acid Membranes
Springer, 2009 - Factors Influencing Ionomer Degradation
John Wiley & Sons, Ltd, 2009 - Graphite Negative Electrodes for Rechargeable Lithium Batteries
Elsevier, 2009 - In Situ SPM Analysis of Interfacial Phenomena in Lithium-Ion Batteries
355-369, World Scientific Series in Nanoscience and Nanotechnology Vol. 7: Scanning Probe Microscopy for Energy Research, D. A. Bonnell and S. V. Kalinin, Eds, World Scientific - Fuel Cells
Handbook of Electrical Engineering, 7th Edition, OHM, 2013 - Improvement of Cycleability and Reduction of Irreversible Capacity of Silicon Negative Electrode
Science and Technology, 2014 - Improvement of Capacity by Controlling of Particle Size of TiO2(B)
Science and Technology, 2014
Works
- Materials and Properties of Low-Temperature Solid Oxide Fuel Cells
2003 -2010 - Surface Reactions on Negative Electrode Materials in Next-Generation Lithium Ion Batteries
2004 - Study on Lithium Iron Phosphate Positive Electrode in Lithium Ion Batteries
2005 -2010 - Technical Development of Electrochemcial Properties of Ionomer Used in Polymer Electrolyte Fuel Cells
2006 -2010 - Preparation of Multi-Functional Composite Fine Particles for SOFCs
2007 - Degradation on Proton Conductive Materials
2007 -2010
Patents
Research Grants & Projects
- Electrode reactions and degradation mechanism polymer electrolyte fuel cells
New Energy Technology Research and Development, 2001 -2009 - In situ analysis of electrode reactions in rechargeable lithium batteries
1992 -2020 - Materials for electrodes and electrolytes in low-temperature solid oxide fuel cells
Funded Research, 1992 -2010 - Next-Generation Lithium Ion Batteries Using High Potential Negative Electrodes
New Energy Technology Research and Development, 2006 -2007 - Development of Highly Active Electrode Catalysts for Fuel Cells
JST Comprehensive Support Programs for Creation of Regional Innovation, 2003 -2008