The effect of oxygen vacancy and spinel phase integration on both anionic and cationic redox in Li-rich cathode materials

Qingyuan Li, De Ning, Dong Zhou, Ke An, Deniz Wong, Lijuan Zhang, Zhenhua Chen, Götz Schuck, Christian Schulz, Zijian Xu, Gerhard Schumacher, Xiangfeng Liu

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119 Scopus citations

Abstract

Tuning the anionic redox chemistry (O2- ? O2n-) activity and reversibility by crystal and/or electronic modulation is essential for Li-rich oxide cathode materials. Herein, we report a facile strategy to improve the activity and reversibility of both anionic and cationic redox by integrating oxygen vacancies and the spinel phase. The initial specific capacity (216.1 mA h g-1vs. 316.3 mA h g-1), coulombic efficiency (80% vs. 94.8%), long-term cycling stability (1000 cycles at 5C) and voltage decay have all been greatly improved due to the largely suppressed irreversible oxygen release. The underlying modulation mechanism has been unraveled. Firstly, the introduction of oxygen vacancies decreases the covalency of TM-O and the density of states of the O 2p band, which mitigates the irreversible oxygen release during oxygen redox. Secondly, the spinel phase integration induced by oxygen vacancies not only improves the Li-ion conductivity and the rate capability due to its 3D Li+ channel and the expanded Li layer but also enhances the structural stability. Thirdly, the first-principles calculations indicate that the increase of delocalized electrons around the transition metal also intensifies the MnO6 octahedral distortion and the inactive Mn-ions are partially activated during the first cycle and participate in the charge compensation. This study sheds some new light on designing high-performance Li-rich layered oxide cathode materials by regulating the anionic and cationic redox with the incorporation of oxygen vacancies and the spinel phase.

Original languageEnglish
Pages (from-to)7733-7745
Number of pages13
JournalJournal of Materials Chemistry A
Volume8
Issue number16
DOIs
StatePublished - Apr 28 2020

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 11575192), the International Partnership Program (Grant No. 211211KYSB20170060 and 211211KYSB20180020), the Scientic Instrument Developing Project (Grant No. ZDKYYQ20170001), the Strategic Priority Research Program (Grant No. XDB28000000) of the Chinese Academy of Sciences, the Natural Science Foundation of Beijing (Grant No. 2182082), and the University of Chinese Academy of Sciences. The neutron experiments benet from the SNS user facilities (VULCAN beamline) sponsored by the office of Basic Energy Sciences (BES) and the Office of Science of the U.S. DOE. The authors also thank the staff at the BL08U1-A beamline of SSRF and at beamline 1W1B and 4B7B (Dr Shuhu Liu) at BSRF for their support. The allocation of beamtime at RGBL, KMC2 and U41-PEAXIS beamlines, BESSY-II, HZB, Germany, is gratefully acknowledged. We are very grateful to Dr Yandong Gong, Dr Yuanyuan Cui and Dr Ting Yin from Shimadzu China Co., Ltd. for the XPS testing and the discussion. This work was supported by the National Natural Science Foundation of China (Grant No. 11575192), the International Partnership Program (Grant No. 211211KYSB20170060 and 211211KYSB20180020), the Scientific Instrument Developing Project (Grant No. ZDKYYQ20170001), the Strategic Priority Research Program (Grant No. XDB28000000) of the Chinese Academy of Sciences, the Natural Science Foundation of Beijing (Grant No. 2182082), and the University of Chinese Academy of Sciences.*%blankline%*

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