炭素
Online ISSN : 1884-5495
Print ISSN : 0371-5345
ISSN-L : 0371-5345
2009 巻, 240 号
選択された号の論文の9件中1~9を表示しています
論文
  • 齊藤 翔太, 笠嶋 貴, 伏見 公志, 金野 英隆
    原稿種別: 論文
    2009 年 2009 巻 240 号 p. 207-212
    発行日: 2009/11/13
    公開日: 2010/12/15
    ジャーナル フリー
    Si/C/O composites were formed by carbonization of Kapton type polyimide films containing 0–10 at% Si. About 24 mass% of Si was present in the composite derived from the polyimide containing 7 at% Si at 1350°C and, by 29Si MAS NMR, they were mainly Si(O)4 type components around −110 ppm with unidentifiable components in a range of −100 to −20 ppm. This composite showed the best performance of Li+ ion insertion/extraction: the coulomb efficiency was nearly 100% except for the 1st cycle and the extraction capacities were 648 mA h g−1 after 10 cycles at 50 mA g−1 and 393 mA h g−1 after 50 cycles at 500 mA g−1, and the latter was increased to ca. 470 mA h g−1 by preliminary cycles at low current densities. After 10 cycles at 50 mA g−1 the components around −110 ppm almost disappeared from the NMR spectrum and a broad and noisy band was observed in a range of −100 to −50 ppm. Since sub-micrometer fused silica particles did not react as the composites performed, the components around −110 ppm are not necessarily silica. The mechanism of reversible insertion/extraction of Li+ ion for the composites was not completely clarified, but the results by cyclic voltammetry and MAS NMR left room for doubt about an alloying/dealloying mechanism between Si and Li.
  • Kazuhito Hoshi, Naoto Ohta, Katsuhide Nagaoka, Shingo Bitoh, Akio Yama ...
    原稿種別: Research Paper
    2009 年 2009 巻 240 号 p. 213-220
    発行日: 2009/11/13
    公開日: 2010/12/15
    ジャーナル フリー
    Carbon coating of substrate graphite powder was carried out by carbonizing the mixture with poly(vinyl alcohol) at 600~1500°C. From the measurement of anode performance on the carbon-coated graphite prepared from 21 graphite substrates, crystallite thickness with three-dimensional regular stacking and BET surface area of the substrate graphite were used as parameters for the selection of the substrate graphite. The production scale of carbon-coated graphite powders was successfully increased up to about 1000 kg. Carbon-coated graphite was shown to give a smaller irreversible capacity for the first charge/discharge cycle than graphite without a carbon coating and could be used in an electrolyte solution containing a small amount of propylene carbonate (PC), of which anode performance was almost comparable with those in the solutions without PC. With a high discharge rate of about 10 mA/cm2, carbon-coated graphite gave better anode performance, larger discharge and smaller irreversible capacities, than the graphite without a carbon coating.
  • 越川 寿利, 等々力 弘篤, 近藤 篤, 服部 義之, 沖野 不二雄, 東原 秀和
    原稿種別: 論文
    2009 年 2009 巻 240 号 p. 221-225
    発行日: 2009/11/13
    公開日: 2010/12/15
    ジャーナル フリー
    The formation of a solid electrolyte interface (SEI) at the surface of a SWNT electrode was investigated by SEM, TEM, XRD, and Raman spectroscopy. These analyses were carried out at different charge-discharge cycles, showing the cycle dependent character of the SEI formation. The changes in chemical species of SEI with increased number of cycles have been examined. This study shows by XRD, that inorganic species of SEI are LiF and Li2CO3, and that the SEI formation depends on the number of discharge-charge cycles.
ノート
  • 白石 壮志, 須永 薫, 菅沼 孝章
    原稿種別: ノート
    2009 年 2009 巻 240 号 p. 226-229
    発行日: 2009/11/13
    公開日: 2010/12/15
    ジャーナル フリー
    Phenolic-resin based steam-activated carbon fiber (ACF) for electric double layer capacitors was subjected to heattreatment at 1500°C in nitrogen. The dependence of the pore structure and the capacitance retention rate after high voltage charging (3 V, 100 h, 70°C) on the heating duration was investigated using a two-electrode cell with propylene carbonate electrolyte. The micropore-shrinkage and the removal of the oxygen-containing surface functionalities of the ACF were accomplished within a short time (5 seconds) by the heat-treatment, however a longer time (1 hour) was necessary to improve the capacitance retention rate. The Raman analysis revealed that the local ordering structure changed slowly by heat-treatment at 1500°C, suggesting the sufficiently long heat-treatment essential to the improvement of the capacitance retention rate.
総合論文
  • 王 立紅, 稲垣 道夫, 豊田 昌宏
    原稿種別: 総合論文
    2009 年 2009 巻 240 号 p. 230-238
    発行日: 2009/11/13
    公開日: 2010/12/15
    ジャーナル フリー
    Performance of electric double layer capacitors (EDLCs) was studied by using different microporous and mesoporous carbons in positive and negative electrodes (symmetric and asymmetric EDLCs) in non-aqueous and aqueous electrolytes (1M TEMABF4/PC and 1M H2SO4, respectively). Microporous carbons were selected from commercially available activated carbons and mesoporous carbons from laboratory-made ones. Asymmetric EDLCs consisting of microporous carbon AC-5 and different mesoporous carbons XX in either the positive or negative electrode (AC-5/XX and XX/AC-5) showed a predominant contribution of the negative electrode, where cations of electrolyte are adsorbed, to capacitance and rate performance. Contributions of the surface due to micropores and that due to other large pores to the EDLC capacitance were separately evaluated as a function of current density for the charge/discharge cycle in two electrolytes. The contribution of microporous surface, Cmicro., is smaller than that of the surface of other large pores, Cext., depending more markedly on current density during the charge/discharge cycle. The values of Cext./Cmicro. are in the range 2.4~2.8 in H2SO4, but 4.3~7.2 in TEMABF4/PC. Cmicro. in TEMABF4/PC is smaller than that in H2SO4, suggesting a smaller contribution of micropores to capacitance in TEMABF4/PC.
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