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タイトル: Direct observation of reversible oxygen anion redox reaction in Li-rich manganese oxide, Li2MnO3, studied by soft X-ray absorption spectroscopy
著者: Oishi, Masatsugu
Yamanaka, Keisuke
Watanabe, Iwao
Shimoda, Keiji
Matsunaga, Toshiyuki
Arai, Hajime
Ukyo, Yoshio
Uchimoto, Yoshiharu
Ogumi, Zempachi
Ohta, Toshiaki
著者名の別形: 大石, 昌嗣
下田, 景士
荒井, 創
右京, 良雄
内本, 喜晴
小久見, 善八
発行日: 16-May-2016
出版者: Royal Society of Chemistry
誌名: Journal of Materials Chemistry A
巻: 4
開始ページ: 9293
終了ページ: 9302
抄録: Li-rich layered oxides have attracted attention as promising positive electrode materials for next-generation lithium-ion secondary batteries because of their high energy storage capacity. The participation of the oxygen anion has been hypothesized to contribute to these oxides' high capacity. In the present study, we used O K-edge and Mn L-edge X-ray absorption spectroscopy (XAS) to study the reversible redox reactions that occur in single-phase Li-rich layered manganese oxide, Li2MnO3. We semiquantitatively analyzed the oxygen and manganese reactions by dividing the charge/discharge voltage region into two parts. The O K-edge XAS indicated that the electrons at the oxygen site reversibly contributed to the charge compensation throughout the charge/discharge processes at operating voltages between 2.0 and 4.8 V vs. Li+/Li0. The Mn L-edge XAS spectra indicated that the Mn redox reaction occurred only in the lower-voltage region. Thus, at higher potentials, the electrons, mainly at the oxygen site, contributed to the charge compensation. Peaks whose energies were similar to peroxide appeared in and then disappeared from the O K-edge spectra obtained during the reversible redox cycles. These results indicate that the reorganization of the oxygen network in the crystal structure affects the redox components. By using two kinds of detection modes with different probing depths in XAS measurements, it was found that these redox reactions are bulk phenomena in the electrode.
著作権等: This is the accepted version of the article, which has been published in final form at http://dx.doi.org/10.1039/c6ta00174b.
The full-text file will be made open to the public on 16 May 2017 in accordance with publisher's 'Terms and Conditions for Self-Archiving'.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
URI: http://hdl.handle.net/2433/219475
DOI(出版社版): 10.1039/c6ta00174b
出現コレクション:学術雑誌掲載論文等

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