Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
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78 巻 , 5 号
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論文特集号 第50回電池討論会記念特集号:革新的なエネルギー貯蔵デバイスとしての二次電池
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  • Motofumi YAMADA, Takayuki KODERA, Takashi OGIHARA
    78 巻 (2010) 5 号 p. 463-466
    公開日: 2012/03/26
    ジャーナル フリー
    Spherical C/Li4Ti5O12 fine powders were successfully prepared by the ultrasonic spray pyrolysis using aqueous solution of Li and Ti with organic compound. C/Li4Ti5O12 particles were crystallized to spinel structure with Fd3m space group at more than 600°C. The carbon content of C/Li4Ti5O12 powders was 5 wt% from DTG analysis. Chemical analysis revealed that the molar ratio of Li/Ti of C/Li4Ti5O12 powders was agreement with the starting solution component. The electrochemical properties of C/Li4Ti5O12 anode were also estimated by rechargeable capacity, cycle life, thermal stability and high rechargeable rate. The use of lactic acid as a carbon source was most effective for improvement of them. The rechargeable capacity of C/Li4Ti5O12 anode increased with increasing carbon contents and it exhibited 165 mAh g−1 at 1 C. The rechargeable capacity of C/Li4Ti5O12 decreased with increasing charge rate and that of C/Li4Ti5O12 was 150 mAh g−1 at 10 C, but the stable cycle life was also maintained at 10 C. The cycle stability of C/Li4Ti5O12 anode was also kept at 50°C.
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  • Yukio SASAKI, Haruhiko SATAKE, Naoko TSUKIMORI, Noritoshi NANBU, Masah ...
    78 巻 (2010) 5 号 p. 467-470
    公開日: 2012/03/26
    ジャーナル フリー
    The physical and electrolytic properties, and charge-discharge characteristics for secondary lithium batteries of partially fluorinated methyl propyl carbonate (MPC) derivatives were examined. Dielectric constants of the fluorinated MPC derivatives except 2,2,3,3,3-pentafluoropropyl methyl carbonate (PFPMC) tend to increase with increasing the number of fluorine atom. Viscosity of PFPMC with the highest molar volume is lower than those of other fluorinated MPC derivatives. Donor numbers (DN) of the fluorinated MPC derivatives were estimated by 29Si NMR chemical shifts of triphenylsilanol. DN of the fluorinated MPC derivatives except PFPMC tends to decrease with increasing the number of fluorine atom. 3-Fluoropropyl methyl carbonate (FPMC) shows the highest specific conductivity at the temperature above about 25°C. Oxidative decomposition potentials of the fluorinated MPC derivatives tend to increase with increasing the number of fluorine atom. PC-FPMC electrolyte shows higher lithium electrode cycling efficiency. Every PC-based fluorinated MPC derivative electrolyte shows higher discharge capacities for Li|LiCoO2 cells.
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  • Irina D. GOCHEVA, Takayuki , Shigeto OKADA, Jun-ichi YAMAKI
    78 巻 (2010) 5 号 p. 471-474
    公開日: 2012/03/26
    ジャーナル フリー
    The electrochemical properties of lithium hexafluorometalates as positive electrode materials were studied. Trirutile-type Li2TiF6 was synthesized through a complex-formation reaction under mild temperature conditions. In addition, a spray-drying technique was used to obtain electrodes with a large surface area. The electrochemical performance of the resultant Li2TiF6 powders was investigated vs. Li metal as negative electrode. Li2TiF6 exhibited an initial discharge capacity of 100 mAh g−1 at 2.7 V.
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  • Yasushi IDEMOTO, Kenichiro UEKI, Naoto KITAMURA
    78 巻 (2010) 5 号 p. 475-481
    公開日: 2012/03/26
    ジャーナル フリー
    We investigated the average, local and electronic structures of LiMn1/3Ni1/3Co1/3O2 prepared by various methods. Their electrode characteristics were also studied by charge-discharge test. As a result, it was demonstrated that the sample synthesized by solution method exhibited the most excellent cycle performance. In order to clarify how the preparation processes affected on the crystal structures in detail, local structure, i.e. cation mixing and transition-metal ordering, in the samples were analyzed by Pair Distribution Function (PDF) method using a neutron source and X-ray absorption fine structure measurements. From this analysis, it was found that the local structure in LiMn1/3Ni1/3Co1/3O2 depended on the preparation process. Such a difference in the local structures may result in different cathode properties among the samples synthesized.
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  • Hiroaki YOSHIDA, Nobutaka IMAMURA, Takefumi INOUE, Koichi TAKEDA, Hito ...
    78 巻 (2010) 5 号 p. 482-488
    公開日: 2012/03/26
    ジャーナル フリー
    Large capacity Li-ion cells with 100 Ah for satellite application had been developed in 1999, and calendar and cycle life characteristics of the cells had 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). These tests were started in 1999, and the data have been accumulated until 2008 for around ten years. From these results, we have confirmed that GYT Space Li-ion cells have sufficient capability to achieve the mission life requirements for several kinds of artificial satellites. Furthermore, we have discovered that our simple life estimation model needs to be modified to consider SEI growth blocking mechanism. It means that the SEI growth is blocked by the adjacent SEI layers, therefore calendar capacity loss is affected by not only its test term, temperature, and state of charge but also its calendar capacity loss values. Our modified estimation formula is that a rate of calendar capacity loss is decreased in proportion to the 2.4th power of the calendar capacity retention. By using the modified formula, the estimation results show very good fitting with the long term cell test data for ten years.
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