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Volume 63, Issue 3
Displaying 1-9 of 9 articles from this issue
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Comprehensive Papers
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Hajime MIYASHIRO, Yo KOBAYASHI, Shiro SEKI, Yasutaka OHNO2006 Volume 63 Issue 3 Pages 139-148
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSAll-solid-state lithium polymer secondary batteries (LPBs) have been studied for the purpose of developing large-scale batteries for electric power load leveling devices. First, we prepared LPBs using a thin-film cathode, and the ‘polymer/ceramic composite concept’ of the LPBs was confirmed. Next, the degradation mechanism of powder-type cathode LPBs was investigated using a combination of several electrochemical methods. It was possible to quantitatively separate the resistances in the LPBs. It was revealed that the degradation of the LiCoO2 cathode/solid polymer electrolyte interface is dominant. Therefore, ceramic electrolyte coated cathode powder was prepared by a mechanical coating technique. As a result, it became clear that the oxidative decomposition, which takes place at the cathode/electrolyte interface, can be controlled by a coating of ceramic electrolyte on cathode powder.View full abstractDownload PDF (1388K) -
Shin-ichi SAWADA, Tetsuya YAMAKI, Masaharu ASANO, Masaru YOSHIDA2006 Volume 63 Issue 3 Pages 149-159
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSFluoropolymer electrolyte membranes for direct methanol fuel cell (DMFC) applications were developed by combining the γ-ray-induced crosslinking with graft polymerization methods. The styrene grafting into crosslinked PTFE films and subsequent sulfonation led to the electrolyte membranes exhibiting higher proton conductivity and lower methanol permeability compared to those of Nafion. Such high performances were considered to originate from the low water uptake due to the crosslinking structure. As a second step, two styrene derivative monomers possessing the hydrophobic hydrocarbon groups on the aromatic rings and two different crosslinkers were graft-copolymerized instead of styrene into poly (ethylene-co-tetrafluoroethlene) (ETFE) films, in which radiation crosslinking occurs at room temperature. The sulfonated electrolyte membranes were obtained by the γ-ray crosslinking after the four-component grafting, showing six times higher oxidation resistance compared to the conventional styrene/divinylbenzene grafted ones, and methanol permeability being ten times lower than that of Nafion. This study revealed the applicability of radiation-processing technology to the research and development of electrolyte membranes for PEFC applications.View full abstractDownload PDF (1121K)
Original Papers
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Hiromori TSUTSUMI, Toru KITAGAWA2006 Volume 63 Issue 3 Pages 160-165
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSNew-type polymer electrolyte films based on poly (acrylonitrile), (PAN), and cyanoethylated poly (vinyl alcohol), (CNPVA), were prepared and their conducting behaviors and structures were investigated. CNPVA was prepared from poly (vinyl alcohol) and acrylonitrile in the presence of sodium hydroxide and quaternary ammonium halide as a phase transfer catalyst. Free standing PAN- and CNPVA-based electrolyte films were prepared by casting the propylene carbonate (PC) solution containing PAN, CNPVA and LiClO4 and removing some amount of PC. The ionic conductivity of the electrolyte film, (PAN) 10 (CNPVA) 10 (LiClO4) 8 (PC) 4 composite film, was 1.46×10-2Scm-1 at 30°C and 2.24×10-2Scm-1 at 60°C. FT-IR results for the electrolyte films suggest that the nitrile groups in the CNPVA matrix strongly interact with the lithium ions in the films and enhance the dissolution of the lithium salt in the electrolyte films.View full abstractDownload PDF (321K) -
Yasuhiro HASHIMOTO, Naoki SAKAMOTO, Hideki IIJIMA2006 Volume 63 Issue 3 Pages 166-173
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSExtensive characterizations of the water, ionic cluster structure, and ionic conductivity of Aciplex® S1001 (polyperfluorosulfonic acid: PFSA membrane) were carried out using IR and SAXS measured under varied relative humidity conditions. States of the water in the membrane were classified into two types: free water and bound water. Each type of water was found to affect the ionic conductivity of the membrane in a different way; particularly, the presence of the free water was necessary for the conductivity. Below the relative humidity of 30%RH, all the water contained in the membrane was bound water. And above 60%RH, a significant increase in the free water was observed. The change of the states of water may be caused by an alteration of the ionic cluster structure when individual clusters appeared to form a connected ionic cluster network. This water behavior, as well as the morphological change of the supermolecular structure of the membrane, accounts for the dramatic increase in the conductivity at 60%RH or above.View full abstractDownload PDF (389K) -
Kota KITAMURA, Yoshimitsu SAKAGUCHI, Satoshi TAKASE, Junko NAKAO2006 Volume 63 Issue 3 Pages 174-181
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSIonic group-containing polybenzoxazoles (I-PBOs) were examined as new heat-resistant ion-conducting polymers. I-PBOs were synthesized by polycondensation of terephthalic acid and sulfo- or phosphophthalic acid with 2,5-diaminoresorcinol dihydrochloride in polyphosphoric acid. I-PBOs were stable up to 390°C and the creep deformation of I-PBOs membranes was only several percent even at 500°C. The rigid and electron-withdrawing benzoxazole units suppress the thermal decomposition of the sulfo-groups. The proton conductivity depends on the content and acidity of the ionic group. I-PBOs with high sulfo contents, e.g. DTT-100, showed conductivity higher than that of Nafion®112. The drastic increase in conductivity and water uptake for DTT-100 above 90% RH suggests that high conductivity requires sufficient free water in the membrane.View full abstractDownload PDF (324K) -
Makoto YUASA, Kenichi OYAIZU, Aritomo YAMAGUCHI, Takuya IMAI, Mizuki K ...2006 Volume 63 Issue 3 Pages 182-188
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESS[Meso-tetra (thiophen-3-yl) porphinato]cobalt(II)(CoT3ThP) complex, which undergoes facile electropolymerization, was synthesized by the dehydro-condensation reaction of pyrrole and 3-thienylaldehyde. The electroconductive thin film of CoT3ThP interconnected by 2,5-thienylene chains, was produced at the glassy carbon electrode by electrolysis. The catalytic activity for oxygen reduction at the modified electrode was evaluated by cyclic voltammetry. The catalytic current for the O2 reduction appeared near Ep = 0.2 V vs. SCE. It was found that the electrode modified with CoT3ThP film has a higher stability than that modified with porphyrin by absorption. Next, we chose carbon black with a high surface-area as a catalyst support, and CoT3ThP was electropolymerized under the condition of suspension of carbon black in an electrolyte solution. We found that the polymerized CoT3ThP was produced on the surface of the carbon nanoparticle. The carbon nanoparticles modified with polymerized CoT3ThP (polyCoT3ThP/C) were suspended in a Nafion solution, and a pseudo MEA (Membrane Electrode Assembly) was made by casting polyCoT3ThP/C on an edge-plane pyrolytic graphite electrode. The polyCoT3ThP/C catalyst was found to reduce O2 mainly with four electrons (the number of electrons transferred n = 3.8) at a positive potential of Ep = 0.44 V vs. SCE. The catalytic activity of polyCoT3ThP/C was improved by heat treatment under an inert gas atmosphere (Ep = 0.47 V vs. SCE, n = 3.8). The results show the possibility of a novel cathode catalyst for use in fuel cells.View full abstractDownload PDF (388K) -
Kenichi OYAIZU, Aritomo YAMAGUCHI, Yuichi IAI, Ken TANAKA, Makoto YUAS ...2006 Volume 63 Issue 3 Pages 189-195
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSConductive polymer ligand-coated carbon particles were prepared by a fluid-bed electrolysis of 2-(3-pyridyl) thiophene using carbon particles as a working electrode. The resulting particles were suspeneded in a DMF solution of cobalt acetate. The surface of carbon particles was successfully modified with the highly dispersed cobalt complex. The modified carbon particles were suspended in an alcoholic solution of Nafion, and a pseudo-MEA was prepared on an electrode by casting the solution. The electrocatalytic reduction of dissolved O2 was examined using the modified electrode. When the catalyst was prepared using a carbon black with a large surface area and pyrrole was added as a complementary ligand, the catalytic potential for the reduction of O2 appeared at Ep = 0.37 V vs. SCE. The catalyst was found to reduce O2 mainly with four electrons (n = 3.1). This activity was superior to that of the previously reported carbon nanoparticles modified with a cobalt polypyrrole complex. It was clearly shown that nitrogen atoms of the pyridine-type ligand contribute to accumulate cobalt ions on the surface of the catalyst. It was also revealed that the catalytic activity improved remarkably after heat treatment of the catalyst under argon. The catalyst revealed the possibility of its use as a cathode catalyst for platinum-free fuel cells.View full abstractDownload PDF (664K)
Notes
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Activated Carbon Fiber Coated with Poly (methoxythiophene) as a High Performance Capacitor ElectrodeNobuko YOSHIMOTO, Masaharu ARAKI, Masayuki MORITA2006 Volume 63 Issue 3 Pages 196-199
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSComposite electrodes made of poly (3-methoxythiophene) (pMeOT) and activated carbon fiber (ACF) were prepared by electro-oxidation of 3-methoxy-thiophene in acetonitrile (AN). The SEM observation of the composites revealed that thin nano-structured polymer films were deposited on the surface of ACF, whose morphologies depended on the polymerization conditions. The electrochemical activities of the composites as capacitor electrodes were examined by cyclic voltammetry and galvanostatic cycling in AN. Capacitance enhancement was observed for both types of composite electrodes prepared differently. “Electrolyte impregnation method” brought about the pseudocapacitance originated from the polymer on the ACF substrate. “Monomer impregnation method” increased the double-layer capacitance based on the porous structure of ACF.View full abstractDownload PDF (439K) -
Takahiko NAKANO, Shoji NAGAOKA, Hiroyoshi KAWAKAMI2006 Volume 63 Issue 3 Pages 200-204
Published: 2006
Released on J-STAGE: September 21, 2007
JOURNAL FREE ACCESSWe have synthesized a novel sulfonated block copolyimide with long block chains by chemical imidization using a two-pot procedure. The proton conductivity of a block copolyimide film, i.e., NTDA-BDSA-b-6FAP (140/60) was approximately 0.45 S cm-1, which is higher than that of Nafion 117®. Additionally, we demonstrated that the proton conductivity of the block copolyimide film strongly depends on the block chain lengths. The conductivities of the block copolyimide films increased with increasing block chain lengths. This may be due to the formation of ionic channels in the copolyimide films and its dependence on the block chain length. We are currently investigating the effects of the morphology and domain size of the block copolyimide film on the proton conductivity.View full abstractDownload PDF (256K)
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