Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 88 , Issue 1
Showing 1-8 articles out of 8 articles from the selected issue
Articles
  • Hui ZHANG, Yanxia DU, Runzhi QIN, Zhenchang XU, Qinglin GU
    2020 Volume 88 Issue 1 Pages 1-7
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 02, 2019
    JOURNALS OPEN ACCESS

    This paper focused on the variation of DC interference parameters and corrosion behavior of X80 steel interfered by 100 V DC potential in Guangdong real soil with 5 different water contents through indoor simulation experiments. The results showed that there existed obvious differences for the current density changes of X80 specimens in various soil conditions with different water contents under interference of 100 V DC potential. At a lower water content (14%, 18%, 21%), the DC current density reached a peak value in a second and then dropped to a stable value rapidly, and the drop rate exceeded 60%. When the water content reached 35% or 43%, the current density reached a peak in about 75 s, and after that there was no obvious downward trend. The stable value accounted for about 80% of the peak value. The corrosion rates in the soil conditions with different water contents of 14%, 18%, 21%, 35%, and 43% were 2.66, 4.12, 5.70, 8.62, and 10.01 µm/h, respectively. The local soil spread resistance contributed to the differences in current density and corrosion rates in different environments. The main corrosion products under HVDC interference were iron oxides such as α-FeOOH, γ-FeOOH, and Fe3O4.

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  • Kun WANG, Dongying JU, Guiying XU, Beibei HAN, Yongfei WANG, Jian ZHAN ...
    2020 Volume 88 Issue 1 Pages 8-13
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 11, 2019
    JOURNALS OPEN ACCESS
    Supplementary material

    The carbon black (CB) is modified successfully by the two-step modifications such as organo-chlorination and organo-sulfuration using the chemical reagents of thionyl chloride and ethanethiol continuously. The organosulfur groups of –C–SR and –COSR forming on the CB surface play the main role to improve the electrochemical performances, which is verified by electrochemical studies. For instance, after carrying out the charge-discharge 100 times, the organosulfur modified CB (MCB) shows the Li+ ion storage capacity at 392 mAh/g, which is higher than CB showing at 176 mAh/g. Furthermore, the improvement storage capacity is attributed to the enhanced capacitive effects which are verified by the detailed measurements of cyclic voltammetry (CV). These results are able to provide effective way to enhance the storage capacity of general carbon materials such as CB, graphite, graphene oxide (GO) and so on.

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  • Chuen-Chang LIN, An-Na WU, Shun-Hong JIANG
    2020 Volume 88 Issue 1 Pages 14-21
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 11, 2019
    JOURNALS OPEN ACCESS

    Carbon nanotubes/graphene composites are grown on nickel foil without additional catalysts by chemical vapor deposition. Next, to improve the anchoring and uniform dispersing of Co(OH)2 onto carbon nanotubes/graphene composites, the carbon nanotube/graphene composites are modified by radio frequency nitrogen-plasma. Then porous Co(OH)2 thin films are galvanostatically electrodeposited onto N-doped carbon nanotubes (CNTs)/graphene composites at different currents and time periods. Finally, the porous Co(OH)2 is transformed into porous Co3O4 by annealing. The charge specific capacity (1290 mAh g−1) reaches a maximum at the galvanostatic electrodeposition condition (current = 1.5 mA and time = 300 s) for the coin cell. Furthermore, Co3O4/N-doped CNTs/graphene possesses higher charge (discharge) specific capacity and better electrochemical stability in comparison to Co3O4/CNTs/graphene for the coin cell (full cell: i.e. lithium-ion battery).

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  • Seonghyeon LIM, Hirokazu MUNAKATA, Kiyoshi KANAMURA
    2020 Volume 88 Issue 1 Pages 22-27
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 25, 2019
    JOURNALS OPEN ACCESS

    Generally, Lithium Vanadium Oxide has a larger volumetric capacity anode active material than that of graphite. Unfortunately, LVO (Li1.1V0.9O2) have some critical weak points, such as low cycle life, low rate capability, low electrical conductivity. To improve those of weakness of LVO, we prepared carbon coated LVO with sucrose successfully and evaluated their electrochemical properties, such as, relatively crystallinity, small particle size, and electrical conductivity. Furthermore, charge transfer resistance and lithium ion diffusivity was measured by EIS and GITT evaluations to understand relationship coated carbon layer thickness and electrochemical properties. From this result, it is necessary to consider the electrochemical parameters such as the electric conductivity, the charge transfer resistance, and the lithium ion diffusivity depending on the amount of the carbon layer in order to improve the electrochemical property by the carbon coating.

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  • Kazunari MIYAZAKI, Yidan DING, Hiroki MUROYAMA, Toshiaki MATSUI, Koich ...
    2020 Volume 88 Issue 1 Pages 28-33
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 25, 2019
    JOURNALS OPEN ACCESS

    In this study, the applicability of Ba(Ce,Co,Y)O3−δ (BCCY) for a cathode of proton-conducting ceramic fuel cells was investigated. The electrical conductivity and transference number of BCCY were significantly affected by a cobalt content in the oxide. It was found that this material showed a mixed conduction of proton, oxide ion, and electron. The addition of cobalt into Ba(Ce,Y)O3−δ mainly increased the electronic conductivity of materials. Composite electrodes with an optimum composition of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–BaCe0.7Co0.2Y0.1O3−δ (50:50 wt.%) exhibited lower polarization for the symmetrical cell test with a BaCe0.8Y0.2O3−δ electrolyte in 6.5% humidified oxygen atmosphere, as compared with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) itself and LSCF–BaCe0.9Y0.1O3−δ (50:50 wt.%) composite electrodes. The power generation test was performed at 600°C–700°C using a BaCe0.8Y0.2O3−δ electrolyte-supported single cell employing a LSCF–BaCe0.7Co0.2Y0.1O3−δ (50:50 wt.%) composite cathode, upon feeding 3% humidified hydrogen and pure oxygen to the anode and cathode, respectively. The cell with a LSCF–BaCe0.7Co0.2Y0.1O3−δ (50:50 wt.%) composite cathode exhibited much higher performance than that with a LSCF electrode. Consequently, the introduction of cobalt into Ba(Ce,Y)O3−δ was an effective strategy for an improvement in an oxygen reduction reaction activity of a cathode material.

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  • Yuki MARUYAMA, Kuniaki NAGAMINE, Ayako NOMURA, Shigeyuki IWASA, Shizuo ...
    2020 Volume 88 Issue 1 Pages 34-38
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: November 25, 2019
    JOURNALS OPEN ACCESS
    Supplementary material

    Both p- and n-type redox reactions for 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) successfully proceeded in ionic liquids, although only p-type redox proceeds reversibly in conventional organic electrolytes. The heterogeneous electron-transfer constants estimated from the cyclic voltammograms were in the range of the quasi-reversible system for both p- and n-type TEMPO reactions in ionic liquids. The rate constant for a p-type reaction in ionic liquids were lower by three orders of magnitude than that in the acetonitrile-based electrolyte due to the high viscosity of the ionic liquids. Quasi-reversible p- and n-type redox TEMPO reactions in the ionic liquid-based electrolyte systems suggest the potential realization totally-organic, flexible, safe, and symmetric organic radical batteries (ORBs) which are composed of TEMPO-based polymers for both positive and negative electrodes. The difference between p- and n-type redox electrode potential was 1.7 V in the tested ionic liquids, a value that suggests the electromotive force of symmetric ORB.

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  • Kiyoshi KOBAYASHI, Tohru S. SUZUKI
    2020 Volume 88 Issue 1 Pages 39-44
    Published: January 05, 2020
    Released: January 05, 2020
    [Advance publication] Released: December 09, 2019
    JOURNALS OPEN ACCESS
    Supplementary material

    We developed an impedance analysis software implementing new function for finding an appropriate initial parameter set for impedance spectrum analysis using an interactive graphical user interface (GUI). This new function can be applied without limitation of the equivalent circuits on the basis of a measurement model. The initial parameter values of an equivalent circuit model, which is represented by a peculiar script, can easily be obtained by selecting a data point using a cursor on the logarithm of frequency versus imaginary part of impedance plot by GUI operation and setting a partial impedance element on the graphic control panel. The partial impedance elements include a resistor, capacitor, inductor, a resistor parallelly connected to a capacitor, Warburg impedance, Gerischer impedance, and Havriliak-Negami impedance. Calculating and setting the initial values of the parameters are performed through GUI control, that is, by simply dragging a cursor and clicking buttons. On the basis of this GUI function, users can easily avoid the divergence of complex nonlinear least square process because the calculation can start from an adequate initial guess.

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  • Yuto YAMADA, Kota SUZUKI, Kazuhiro YOSHINO, Sou TAMINATO, Takahiro SAT ...
    2020 Volume 88 Issue 1 Pages 45-49
    Published: January 05, 2020
    Released: January 05, 2020
    JOURNALS OPEN ACCESS

    Lithium distribution in the composite electrode of an all-solid-state lithium battery was analyzed by microbeam-particle-induced X-ray emission and gamma-ray emission techniques. Two kinds of pellet-type cells, incorporating LiCoO2 as the cathode-active material and the superionic conductor Li10GeP2S12 as the solid electrolyte, were prepared: one in the as-prepared state and the other in the charged state. Changes in the lithium distribution near the interface of the composite cathode and separator were visualized by normalizing lithium/cobalt and lithium/germanium intensity. Lithium extraction from LiCoO2 due to charging was confirmed by the decrease in normalized intensity at the cathode composite region. The evaluation of the lithium concentration variation in the composite electrode for the all-solid-state battery during the electrochemical reactions could provide essential information for construction of a favorable composite electrode to enable preparing high-performance all-solid-state lithium batteries.

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