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Title: Direct observation of layered-to-spinel phase transformation in Li2MnO3 and the spinel structure stabilised after the activation process
Authors: Shimoda, Keiji  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0003-4600-3437 (unconfirmed)
Oishi, Masatsugu
Matsunaga, Toshiyuki
Murakami, Miwa  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0001-6209-4450 (unconfirmed)
Yamanaka, Keisuke
Arai, Hajime
Ukyo, Yoshio
Uchimoto, Yoshiharu  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0002-1491-2647 (unconfirmed)
Ohta, Toshiaki
Matsubara, Eiichiro
Ogumi, Zempachi
Author's alias: 下田, 景士
大石, 昌嗣
右京, 良雄
内本, 喜晴
松原, 英一郎
小久見, 善八
Issue Date: 2-May-2017
Publisher: Royal Society of Chemistry
Journal title: Journal of Materials Chemistry A
Volume: 5
Issue: 14
Start page: 6695
End page: 6707
Abstract: Li2MnO3 is an important parent component in lithium- and manganese-rich layered oxides (LMRs), which are one of the promising positive electrode materials for next-generation lithium ion rechargeable batteries. Here, we report the layered-to-spinel phase transformation in Li2MnO3 during the initial charging process to characterise its unique delithiation behaviour, which gives an insight into the relationship between the structure, superior capacities and degradation of LMR electrodes. The atomic-scale observation using scanning transmission electron microscopy (STEM) techniques suggests that the structural transformation occurs in a biphasic manner within a single particle. The formed phase has a Li-defect spinel structure, indicating that the delithiation leads to Mn migration from the transition-metal layer to the Li layer, accompanied by some oxygen release. This layered-to-spinel phase transformation is an essential bulk process in the initial activation of Li2MnO3. During the lithiation in the 1st discharge, the Mn remigration occurs and the layered structure is again formed with significant disordering. During the multiple cycles, the defect spinel structure is stabilised and becomes more oxygen-deficient with a lower Mn valency. As a consequence, the amount of inserted Li decreases, which corresponds to the capacity and voltage fading observed in Li2MnO3 and LMRs.
Rights: This is the accepted version of the article, which has been published in final form at http://dx.doi.org/10.1039/c6ta11151c.
The full-text file will be made open to the public on 02 May 2018 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/2433/224984
DOI(Published Version): 10.1039/c6ta11151c
Appears in Collections:Journal Articles

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