Unraveling vacancy-induced oxygen redox reaction and structural stability in Na-based layered oxides

[Display omitted] •Vacancy introduced sodium cathode provides a new strategy for better performance.•A strong correlation between vacancy and anionic redox activity is observed.•Combined experimental and theoretical studies prove the validity of vacancy control.•This study paves the way toward devel...

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Published in:Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-03, Vol.431, p.133962, Article 133962
Main Authors: Islam, Mobinul, Akbar, Muhammad, Han, Daseul, Ali, Basit, Jeong Choi, Yong, Lee, Jaewoon, Choi, Gwanghyeon, Park, Jae-Ho, Kim, Ji-Young, Jung, Hun-Gi, Yoon Chung, Kyung, Kim, Duho, Kang, Yong-Mook, Nam, Kyung-Wan
Format: Article
Language:English
Subjects:
Anionic redox
DFT calculation
Sodium-ion battery
Transition metal vacancy
X-ray absorption spectroscopy
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Summary:[Display omitted] •Vacancy introduced sodium cathode provides a new strategy for better performance.•A strong correlation between vacancy and anionic redox activity is observed.•Combined experimental and theoretical studies prove the validity of vacancy control.•This study paves the way toward developing advanced cathodes for NIBs. The promising P2-layered sodium manganese oxide (Na2/3MnO2) cathode often suffers from multiple structural transformations due to the Jahn–Teller distortion induced by Mn3+, hence the rapid capacity falloff. Other than many previous studies on partial substitution of Mn by low valence ions, here we have introduced vacancies into Mn sites in P2-Na2/3MnO2 (e.g., Na2/3[□1/6Mn5/6]O2, where □=vacancy) to oxidize Mn close to Mn4+. Combined experimental and theoretical studies reveal that such vacancy introduction overcomes the detrimental structural distortion due to irreversible phase transitions to O2 and OP4 and triggers oxygen redox activated by an orphaned O 2p state around Mn vacancies in addition to the conventional cationic redox. P2-Na2/3[□1/6Mn5/6]O2 shows smooth and continuous charge/discharge curves indicative of restrained phase transitions, leading to much superior cycling stability than the Jahn-Teller distorted pristine counterpart. This study demonstrates the critical role of transition-metal vacancies in triggering the anionic redox reaction and manipulating the phase transitions in P2-type layered cathodes.
ISSN:1385-8947
1873-3212
DOI:10.1016/j.cej.2021.133962