Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 71 , Issue 12
Showing 1-50 articles out of 65 articles from the selected issue
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Headline
  • Zempachi OGUMI, Soon-Ki JEONG
    2003 Volume 71 Issue 12 Pages 1011-1017
    Published: December 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    We report herein on the mechanism for surface film formation on graphite negative electrodes of lithium-ion batteries in several ethylene carbonate (EC)- and propylene carbonate (PC)-based electrolyte solutions. This review is based on extensive studies of surface morphology changes of graphite during charging and discharging and ion-solvent interactions in various non-aqueous electrolyte solutions. In situ electrochemical scanning probe microscopy (SPM) was used as a main analytical tool, and effects of co-solvents on surface film formation in EC-based solutions, effects of film-forming additives on surface film formation in PC-based solutions, and growth of surface film are discussed and reviewed in this article.

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Comprehensive Paper
  • Hiroaki YOSHIDA, Nobutaka IMAMURA, Takefumi INOUE, Kanemi KOMADA
    2003 Volume 71 Issue 12 Pages 1018-1024
    Published: December 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    Large capacity Li-ion cells with 100 Ah had been developed to meet the requirements of space applications. These cells are organic-electrolyte Li-ion cells of LiCoO2/Graphite systems. Calendar and cycle life characteristics of the 100 Ah Space Li-ion cells have been evaluated under various test conditions with wide range of temperature (0°C-60°C), depth of discharge (3%-80% DOD), and state of charge (0%-100% SOC). The test was started in June 1999, and the data have been accumulated for around four years. From these results, based on our capacity loss mechanism, we have confirmed that the calendar and cycle capacity loss of the Li-ion cells can be calculated by using simple formulas. To calculate the calendar capacity loss, multiply the rate constant (kf) by the square root of storage time. The rate constant kf is function of temperature and SOC, and we have confirmed that the kf is affected by electrical potential of a negative electrode. To calculate the cycle capacity loss, multiply the rate constant (kc) by the square root of cycle number. The rate constant kc is function of DOD, and we have confirmed that the kc is not affected by temperature in the range of 15°C to 60°C. Our life estimation results shows that our Space Li-ion cells have sufficient capability to achieve the mission life requirements for several kinds of artificial satellite such as geostationary orbit satellites (GEOs) and low earth orbit satellites (LEOs).

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