Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
Volume 84 , Issue 8
Showing 1-16 articles out of 16 articles from the selected issue
Preface
Comprehensive Paper
  • Shotaro HAYASHI, Toshio KOIZUMI
    2016 Volume 84 Issue 8 Pages 570-573
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    We have demonstrated a chloride-promoted direct arylation of 6,6′-dibromo-N,N′-(2-ethylhexyl)isoindigo, ID, with 4.0 equivalent of 3,4-ethylenedioxythiophene, EDOT, giving a small band gap donor-acceptor oligomer, 6,6′-bisEDOT-N,N′-(2-ethylhexyl)isoindigo, BEDOTID in 97% yield. The polymerization of BEDOTID was performed by following two approaches; (1) electro-oxidative (homo-coupling) reaction in dichloromethane and (2) Pd-catalyzed oxidative (homo-coupling) reaction in chloroform. These approaches afforded insoluble poly[bis-EDOT-isoindigo], PBDOTID. Characterization of PBEDOTID was performed with the film prepared by electro-oxidative polymerization, which showed low optical and electrochemical band gap properties (1.33 and 1.28 eV, respectively) based on the electron-donating EDOT and electron-accepting isoindigo units. The measurement of the current density on scan rate justified that the obtained PBEDOTID film was uniform.
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Articles
  • Hongyu FAN, Xiaoqing LI, Huiqiu HE, Na PENG, Ying HAN, Zhen LIU, Mingj ...
    2016 Volume 84 Issue 8 Pages 574-577
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    Silicon monoxide (SiO) is utilized as an anode material in Li-ion batteries. The electrochemical properties of the SiO anodes are investigated. The SiO exhibits a high initial capacity of ∼2083 mAh g−1, while it has poor cycling stability. Thermal properties of SiO electrodes in mixing with or without the electrolyte are investigated by using DSC for the first time. Both lithiated and delithiated SiO electrodes show exothermic peaks in DSC curves, presumably due to the decomposition of electrodes. By changing the ratio between the cycled electrodes to the electrolytes, thermal behavior of the mixtures is studied in detail. The dominant exothermic peak at around 290°C is attributed to the reactions between lithiated electrode and electrolyte after the thermal breakdown of the SEI. Li in the electrodes and electrolytes should be responsible for the thermal risk in application of SiO batteries. The heat value of SiO based on capacity is estimated to be 1.85 J mAh−1, which is much smaller than that of graphite (5.11 J mAh−1). Hence, the SiO can be thermally safer than graphite.
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  • Xiaoxiang SUN, Jianxi ZHAO
    2016 Volume 84 Issue 8 Pages 578-584
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    The effect of fumed silica (F-SiO2) density on the performance of valve-regulated lead-acid (VRLA) batteries, including the conductivity of H+ ions and the diffusion of HSO4 ions in the gel electrolyte, the redox capacity of lead, and the evolution of hydrogen and oxygen, have been studied over a wide range of F-SiO2 densities. The results show that the influence of F-SiO2 density is not monotonous and always yields a maximum (or inflection) effect at c. 5 to 6 wt% silica, before and after which the effect of F-SiO2 differ. At lower F-SiO2 densities, in general, gel formation favours an improvement of the electrochemical behaviour. However, it may produce an adverse effect on the electrochemical properties if F-SiO2 density further increases. Battery tests at a range between 1 to 3 wt% silica support this observation, in which the discharge capacity, the utilisation of active materials, and the charge efficiency are all enhanced.
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  • Zhi-Ming GAO, Xi-Bo LU, Da-Hai XIA, Li-Xia YANG, Ren-Kang ZHU, Yashar ...
    2016 Volume 84 Issue 8 Pages 585-596
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    Interaction of thiosulfate with Alloy 800 was systematically investigated to obtain the kinetics in a neutral simulated steam generator crevice solution. Cyclic polarization showed that the pitting potential in a thiosulfate-chloride solution was much lower than in either a chloride solution or a sulphate-chloride solution, and thiosulfate selectively and distinguishably degraded the oxide film on Alloy 800. The donor density of oxide film formed in a thiosulfate-chloride solution was slightly higher than in either a chloride-only solution or a sulphate-chloride solution. Even in the passivity range the material was degraded due to the slow interaction with S2O32− with oxide, especially when the applied potential was close to the pitting potential. The UV-visible absorption spectra showed that thiosulfate formed a stable complex with Cu2+, and their product was soluble in aqueous solution, which is possible evidence to indicate that thiosulfate assists Cu2+ in dissolving from an oxide film into solution. Also, due to the complexity of the reaction, thiosulfate decreased the oxidation potential of Cu0 to Cu2+. Since the Cu, an impurity in Alloy 800, normally accumulates at the grain boundary, especially at the triple points, thiosulfate induced corrosion is in the form of pitting or intergranular attack.
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  • Ayuko KITAJOU, Kosuke TANAKA, Hidenori MIKI, Hideyuki KOGA, Toshihiro ...
    2016 Volume 84 Issue 8 Pages 597-600
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    Although Li2MnTiO4 has a large theoretical capacity (295 mAh g−1), the cathode utilization is limited due to the mixed cation occupation in the disordered rocksalt structure. In this study, we have attempted to prepare single-phase Li2+2xMn1−xTi1−xO4 compositions (0 ≤ x ≤ 0.3) with Li excess to further improve the cathode properties of Li2MnTiO4. The rechargeable capacity of the synthesized Li2.4Mn0.8Ti0.8O4 composition was above 220 mAh g−1, which is larger than those of other disordered Li2MTiO4 (M = Ni, Co, Mn and Fe) series. Moreover, the discharge capacity of Li2.4Mn0.8Ti0.8O4 was ca. 190 mAh g−1 after the 15th cycle, and its capacity retention was 82%.
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  • Kohei TANAKA, Yoshitsugu SONE, Omar S. MENDOZA-HERNANDEZ, Seisuke FUKU ...
    2016 Volume 84 Issue 8 Pages 601-604
    Published: August 05, 2016
    Released: August 05, 2016
    JOURNALS OPEN ACCESS
    The AC impedance of the LiFePO4 type lithium-ion secondary cells was initially measured, and charge/discharge cycling was constantly repeated at 10, 23, and 45°C to understand their electrochemical characteristics. The decrease in the impedance for the charge transfer was observed at each temperature even though the SOC was set in 50%. We assumed from the impedance changing and discharge trend that the negative electrode performed as a “lithium-ion reservoir” by cycles.
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