Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 81 , Issue 6
Showing 1-18 articles out of 18 articles from the selected issue
Preface
Articles
  • Takamasa OHTOMO, Akitoshi HAYASHI, Masahiro TATSUMISAGO, Koji KAWAMOTO
    2013 Volume 81 Issue 6 Pages 428-431
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    The Li2O-Li2S-P2S5 glasses, which were prepared by a reaction of the Li2S-P2S5 glass and Li2O, hardly generated H2S gas in air. These glasses showed relatively high ion conductivities about 10−4 S cm−1 at room temperature. However, these conductivities were lower than those of original sulfide glasses. In this study, an addition of LiI to the Li2O-Li2S-P2S5 glasses was examined in order to improve ion conductivities. The 30LiI·70(0.07Li2O·0.68Li2S·0.25P2S5) glass showed high ion conductivity of 1.3 × 10−3 S cm−1 at room temperature, and hardly generated H2S gas in air. On the other hand, the 30LiI·70(0.07Li2O·0.68Li2S·0.25P2S5) glass was electrochemically stable in the potential range of 0–10 V. Moreover, the all-solid-state C/LiCoO2 cell using the 30LiI·70(0.07Li2O·0.68Li2S·0.25P2S5) glass as solid electrolytes worked as lithium secondary batteries at room temperature, and exhibited a good cycle performance. Therefore, the 30LiI·70(0.07Li2O·0.68Li2S·0.25P2S5) glass was a suitable electrolyte for all-solid-state cells because the glass had high conductivity, wide electrochemical window and high chemical stability to moisture.
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  • Jun TOWADA, Yoshihiro KADOMA, Kazuaki SHIMADA, Naoaki KUMAGAI, Koichi ...
    2013 Volume 81 Issue 6 Pages 432-439
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    We have reported that the electrochemical characteristics of a natural graphite (NG-3) electrode in the chloroaluminate type room-temperature ionic liquid containing lithium ion as the electrolyte for non-flammable lithium-ion batteries were improved by employing polyacrylic acid (PAA) as the binder. Therefore, we have analyzed the influence of the binder types on the electrochemical reaction (charge-discharge reaction) of the natural graphite electrode in more detail. The FE-SEM observations showed that the surface morphology of the NG-3 electrode coated with the PAA binder was smooth, whereas that of the NG-3 electrode using poly(vinylidene difluoride) as a binder was rough. The EDX mappings showed that the reduction of SOCl2 and the deposition of Al would be suppressed to some extent during charging by employing the PAA binder; the deposit from the surface of the NG-3 electrode coated with the PAA binder would be exfoliated or disappeared during discharging. Based on the XPS results, it was clarified that Al would be deposited on the surface of the NG-3 electrode during charging. These results clarified that the deposition reaction that was a side reaction was different according to the binder types during initial charging; the exfoliation or the disappearance of the deposit occurred during discharging.
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  • Kazuyuki TATEISHI, Hiroyuki OGINO, Akiko WAKI, Takahiro OHISHI, Mutsua ...
    2013 Volume 81 Issue 6 Pages 440-447
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    We investigated the anodic oxidation of aluminum in ionic liquids (ILs) by the constant-voltage rising rate (C-V) method and constant-current density (C-C) method, with characterization by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The structure of the oxide layer and the reaction efficiency varied with the type of IL, the applied voltage, the forming method, and the water content. A homogeneous Al2O3 film with a superior dielectric property was formed by the C-V method (100 mV/s) in 1-butyl-3-methylimidazolium benzoate (BMIm-BEN, water content 0.81 wt%) at 40 V. Although a homogeneous barrier-type Al2O3 film was also formed in 1-butyl-3-methylimidazolium mandelate (BMIm-MAN, water content 0.34 wt%) at 40 V, some anion species existed in the film, and its jump-voltage characteristics was inferior to that of the film formed in BMIm-BEN. The relative permittivity of the film formed in BMIm-BEN was almost equal to that of the Al2O3 film formed in adipate (1.0 wt%) aqueous solution, but the dielectric constant of the film formed in BMIm-MAN was 1.5 times larger. In contrast, a heterogeneous porous Al2O3 film containing a large amount of anion molecules was formed in 1-ethyl-3-methylimidazolium acetate (EMIm-ACE, water content 0.79 wt%) at 40 V. Since the source of oxygen for anodic oxidation is the small amount of water in the ILs, the water content strongly affected the characteristics of the formed Al2O3 layer.
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  • Naoto KITAMURA, Naoki HAMAO, Sven C. VOGEL, Yasushi IDEMOTO
    2013 Volume 81 Issue 6 Pages 448-453
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    In this work, we prepared LaSrGa1−xMgxO4−δ with the K2NiF4-type layered perovskite structure and then investigated the electrical conduction property and the crystal structure. From the conductivity measurements, it was indicated that LaSrGaO4 exhibited oxide-ion conduction by substituting Mg for Ga partially, but the conductivity of the substituted sample was lower than those of LaGaO3-based materials reported previously. In order to clarify the reason of the lower conductivity, we performed the Rietveld and Pair Distribution Function (PDF) analyses using neutron scattering data, and also carried out first principle calculation as a theoretical approach. As a result, it was indicated the material had a two-dimensional oxide-ion conduction pathway and the oxygen vacancy tended to be localized at the corner sharing position of GaO6 within the perovskite layer. In addition, it was suggested that the low ionic conductivity in the LaSrGaO4-based materials were caused by a large distortion around the defect and a large repulsive force between the oxygen vacancy and La3+.
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  • Nguyen Duc HUNG, Mai Van PHUOC, Nguyen Minh THUY, Nguyen Nhi TRU
    2013 Volume 81 Issue 6 Pages 454-459
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    Nanosilver colloidal solution with strong bactericidal effect has been widely applied in numerous fields. Instead of using other known methods, the colloidal solution was prepared by anodic dissolution of silver under high DC voltage in doubly distilled water. Highly pure colloidal solution with particle sizes from 2 to 40 nm and concentrations of up to 700 ppm were obtained. Their low electrical conductivities indicated that these colloidal solutions did not contain free ions. The Zeta potential values ranged from −28.83 to −38.91 mV, in the region of stable colloid systems. Anodic dissolution process followed electrochemical mechanism, where concentrations of the colloidal solutions determined by the weight loss method were less than the values calculated by anodic current according to Faraday’s law. It was also demonstrated that the process included water decomposition with gas evolution at the electrodes and the generated hydrogen took part in reduction reaction to form nano silver particles in the solution.
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  • Hidenori YAMADA, Wenwen ZHAO, Hideyuki NOGUCHI
    2013 Volume 81 Issue 6 Pages 460-466
    Published: June 05, 2013
    Released: June 05, 2013
    JOURNALS OPEN ACCESS
    The lithium rich layered Li[Li1/5Ni1/5Mn3/5]O2 materials were prepared by mixing the Ni-Mn carbonate precursor with LiOH and followed by calcining at 800–1000°C. It was found that the charge/discharge curves of samples calcined at 800, 900°C tend to transform to spinel-like one, while the sample calcined at 1000°C maintains its original shape even after 30 cycles at 50°C. Rate of structure change depends on the crystallinity of samples and it would relate to the amount of oxygen release from the particle surface during the initial charge. Such oxygen release reaction predominantly proceeds beyond the initial charge capacity of 250 mAh g−1. Layered crystal structure finally changes to poorly crystalized rock-salt structure.
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