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In our presentation, lattice and grain boundary diffusion behavior of Co into (La, Sr)(Ga, Mg)O3 used as an electrolyte in low-temperature operating SOFC will be discussed using diffusion profile data obtained by employing SIMS.

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LaSrGa_1-xMg_xO_4-d consists of the same elements as La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 and has similar crystal structure.La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 is superior oxide ion conductor, therefore it is expected that LaSrGa_1-xMg_xO_4-d exhibits highly oxide ion conducting property. The author expects that the conductivity of Mg-doped LaSrInO₄ derived from cell volume is higher than that of Mg-doped LaSrGaO4.In this presentation, we report synthesis and oxide ion conduction property of LaSrGa_1-xMg_xO_4-d(0 ≤ x ≤ 0.15) and LaSrIn_0.8-yGa_0.2Mg_yO_4-d (0 ≤ y ≤ 0.15) .

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It is considered that tolerance factor would be a key factor in designing highly oxide ion conductor with perovskite. La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 exhibits fast oxide ion conducting properties and tolerance factor is 0.959. The authors have controlled tolerance factor of LaGa_0.9Mg_0.1O_2.95 by doing Gd for a part of La site and Al for a part of Ga site in order to make highly oxide ion conducting compounds. In this presentation, we reported relationship between tolerance factor and oxide ion conductivity for Gd- and Al-doped LaGa_0.9Mg_0.1O_2.95.

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The authors have fabricated low temperature operating SOFC using by electrophoretic deposition technique. We have reported about power generation property of SOFC supported by LSGM electrolyte. In this presentation, the fabrication process for YSZ electrolyte thin film on NiO-YSZ substrate and power generation property of the SOFC will be reported.

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A sulfur-based hybrid cycle for electrolysis and thermal decomposition in high temperature gas-cooled reactor is considered to be a highly efficient hydrogen producing process. The electrodes must satisfy the following requirements; (i) high corrosion resistance in H₂SO₄ solution,and (ii) high electrical conductivity, In this study, electrical conductivity and corrosion resistance in H₂SO₄ solution of A-site doped SrTiO₃ perovskites will be reported.

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Effective utilization of the waste exhausted by producing nickel hydride battery is expected.In this study, conversion of the waste into CH₄ reforming catalyst and its performance have been investigated. The sample prepared from this waste had relatively high CH₄ conversion and stability.

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Proton conductive inorganic-organic membranes supported by glass papers were prepared from 3-glycidoxypropyltrimethoxysilane, tetraalkoxysilane and orthophosphoric acid to reduce the thickness of membranes without loss of mechanical strength. Hybrid membranes with a thickness of about 50-80 micrometer were obtained by using a glass paper about 40 micrometer thick. The conductivity of the membrane with P/Si of 1.5 was about 1.0 x 10^-3 S cm^-1 at 130 ^oC and 7 % relative humidity. The power density of 120 mW cm^-2 were obtained from the test cells using the membrane supported by glass paper. These cells operated continuously for 50 hours.

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Direct methanol fuel cells (DMFCs) have attracted considerable attention as promising power sources for mobile and stationary applications. Perfluorosulfonated polymer membranes have been used as polymer electrolyte membranes. However they are easily expanded by an immersion into water or methanol, which should result in methanol permeation through the membrane. Recently, we developed the composite membranes consisting of gel electrolyte and three-dimensionally ordered silica matrix. They exhibited low methanol cross-over due to the suppression of polymer expansion by the silica matrix. In this study, ordered macroporous membrane of polyimide, which might work as proton conductor by itself, was fabricated and evaluated as a matrix of composite electrolyte for fuel cell.

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Composite electrolyte membranes consisting of porous ceramic matrix and gel electrolyte have been studied for new type of polymer electrolyte fuel cell. However, low mechanical strength of ceramic composite membranes makes it difficult to fabricate membrane electrode assemblies (MEA) by ordinary hot press method. In this study, we developed electrophoretic deposition for MEA fabrication. By using this method, the thickness and density of catalyst layer on a composite membrane was easily controlled, and there was little mechanical stress in deposition process.

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A direct methanol fuel cell (DMFC) has been expected as promising power sources for mobile and stationary applications. For practical applications of DMFC, however, it is necessary to restrain methanol cross-over caused by swelling of ion exchange membrane. We reported a composite electrolyte membrane consisting of gel electrolyte and three-dimensionally ordered silica matrix, which exhibited a low methanol cross-over due to the suppression of polymer expansion by the silica matrix. It is well known that silanol groups (Si-OH) react with various organosilane compounds. So, one can introduce desired properties on glass surfaces. In this study, we developed new conductive path for protons by surface modification of porous silica membrane and optimized its reaction condition.

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Direct Methanol Fuel Cells (DMFC) are considered as candidate technology for applications in stationary, transportation as well as electronic power generation purposes. To develop a high performance direct methanol fuel cell (DMFC), the shape of electrolyte membrane should be stable to improve catalytic reaction and methanol cross over should be reduced. One of the approaches to increase the stability of the polymer electrolyte against swelling or thermal degradation is to bond it with an inorganic material physically or chemically. In this paper we present new generation polymer electrolytes in the pores of an inorganic mesoporous membrane to improve the stability of the membrane. In this case, methanol crossover values were significantly lower than original polymer electrolyte membranes. The processing of membranes for this fuel cell will be detailed in the presentation.

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[in Japanese]

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Recently, we found that platinum nanotubes are synthesized from mixed surfactant liquid crystal templates. A similar but a little modified templating method was applied to the reduction of metal salts to obtain sponge- and layer-like platinum with a primary particle diameter of several tens of nanometer.

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NaCo₂O₄ and Ca₃Co₄O₉ as thermoelectric material ceramics were fabricated by spark plasma sintering method. NaCo₂O₄ and Ca₃Co₄O₉ powder were synthesized by thermal decomposition of metal complex method. Co(NO₃)₂•6H₂O and CH₃COONa or Ca(NO₃)₂ were used as raw materials, and citric acid and EGMME were used as complexation/polymerization agents. The metal salts were dissolved in the solvent which citric acid dissolved with EGMME. NaCo₂O₄ and Ca₃Co₄O₉ fine powders could be obtained easily by heat treatment at 800C in air. These fine powders were sintered by SPS respectively. The high dense ceramics were obtained by only 1min treatment.

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Partially substiuted lithium mannganese spinel oxides are promising for the cathode active material at 4V range for lithium ion batteries. WhileLiNi_0.5Mn_1.5O₄ has an ordered-type structure and shows high capacity on the charge-discharge at 5V range. It became clear that the introduction of defect in the latter spinel oxides forms a disordered-type structure whichleads to high rate capability compared with the stoichiometric phase. Coulombpotential calculation by MD simulation showed that easier diffusion of lithiumin the disoredred-type structure. This result strongly supported the experimental data. In my lectrure the relation of the structure control and the rate property will be introduced.

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The polycrystalline sintered thallium compounds were prepared and the thermoelectric properties were evaluated. The thermal conductivity, electrical resistivity, and Seebeck coefficient were measured from room temperature to 600 K. The thallium compounds have a potential to be good thermoelectric materials because of their extremely low thermal conductivities.

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[in Japanese]

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The initiation sites for tunnel pitting on Al were controlled by patterning the masking film on Al. This process includes the formation of a thin insulating film (poly chloroplene, PC) on an elastomeric hole-array stamp and the transfer of the film to Al by contact printing. The PC film with the hole-array configuration functioned as a mask for the electrochemical etching of Al, and highly ordered tunnel pits with 5 µm intervals were obtained. This method will be useful for the fabrication of highly ordered tunnel pits on Al, which optimizes the surface area of Al for electrolytic capacitors.

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[in Japanese]

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Although lithium batteries are a commercial reality, there is still room for further improvement of their performance. For instance, it would be greatly desirable to replace the present high cost and toxic LiCoO ₂ with more affordable and environmentally benign cathode materials. A convenient candidate is the phospho olivine LiFePO₄, which is cheap, disposable and characterized by a flat voltage profile. However, the performance of this material is controlled by diffusion kinetics of LiFePO₄ in part associated to its low electronic conductivity .The solution of the problem is provided by suitable modifications at the nanoscale level, e.g., dispersion of nanoparticle metals and/or advanced nanofibril morphologies. Among negative electrodes, lithium metal alloys and disordered carbons may be considered as alternatives to graphite. However these materials suffer of decay in capacity, both by initial irreversibility and by cycling decay. Interesting materials are spinel lithium titanium oxides which are characterized by a stable voltage and almost zero structural strain processes.Lithium iron phosphate and lithium titanium oxide may be combined in new types of polymer electrolyte lithium ion batteries which are characterized by a high level of safety and reliability.

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In the realization of all solid-state rechargeable lithium battery, improvement of interface contact between the solid electrolyte and active electrode materials is one of the most important. In order to solve above problem, we have developed new battery design using monodisperse spherical particles of active materials or electrolyte. In this study, monodisperse Li₄Ti₅O₁₂ microspheres as an anode material was prepared by sol-gel process and electrochemical property of three-dimensionally ordered Li₄Ti₅O₁₂ microspheres onto platinum plate was examined.

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The application of Sn-based materials to the anode of rechargeable Li battery system have attracted many researchers due to the high theoretical capacity as anode of Sn alloy with Li. The issue to be solved to utilize the Sn is drastic volume change during the alloying and de-alloying with Li. Sn nano-particle dispersed in Li2S matrix is one of the promising candidates. Moreover, Ni-Sn alloy system is proposed to be the candidate due to its high reversibility and high capacity. At the presentation, our concept to develop the novel anode material for Li ion battery will be introduced and discussed.

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Li₂S-P₂S₅-based glass-ceramics were prepared by mechanical milling and subsequent heat-treatment. In the systems Li₂S-P₂S₅-GeS₂ and Li₂S-P₂S₅-SiS₂, the conductivities increased with an increase in the heat-treatment temperature and exhibited high values over 10^-3 S•cm^-1 after heating at 550 oC. The high conductivities were mainly caused by the formation of superionic crystals analogous to thio-LISICON in the Li₃PS₄-Li₄GeS₄ solid solutions. All-solid-state cells such as In-Li / Li_4/3Ti_5/3O₄ using the highly conductive glass-ceramic electrolytes worked at room temperature and maintained high charge-discharge capacities of over 100 mAh•g^-1 even at the 300th cycle.

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The Li₂S-P₂S₅ glasses were prepared from the mixture of Li₂S, P and S by using mechanical milling. Electrical properties and local structure of the glasses were investigated. These glasses contained PS₄^3- and P₂S₆^4- units, while the glasses obtained from Li₂S and P₂S₅ contained PS₄^3- unit. The glass-ceramics were prepared by the heat-treatment of these glasses above the crystallization temperature. Raman spectra suggested that the glass-ceramics contained PS₄^3- unit. The conductivity of the glass-ceramics was more than 10^-4 S/cm at room temperature.

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Sulfide glassy materials in the system SnS-P₂S₅were prepared by mechanical milling. Thermal properties and local structure were examined for the obtained materials. All-solid-state cells were fabricated with the SnS-P₂S₅ glasses as an electrode and highly conductive Li₂S-P₂S₅ glass-ceramics as an electrolyte. Because of using a common P₂S₅ component, a continuous sulfide network between electrolyte and electrode would be formed in the cells. An All-solid-state cell 80SnS•20P₂S₅ / 80Li₂S•20P₂S₅ / LiCoO₂ exhibited excellent charge-discharge performances at room temperature. The average cell potential was 3.3 V and the cell retained high capacities over 400 mAh/g during charge-discharge cycling for 50 times.

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In order to fabricate all solid-state rechargeable lithium battery with a high discharge capacity, a three-dimensional matrix consisting of solid electrolyte and active material has to be developed. We prepared Li_0.35La_0.55TiO₃ with an inverse opal structure by colloidal crystal templating method using mono-dispersed polystyrene beads (3 mm in diameter). After heat treatment at 1000 deg C, macroporous disk shape membrane with 10 mm size was successfully obtained. The membrane had porous structure and was crystallized.

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[in Japanese]

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