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Oxygen redox in hexagonal layered NaxTMO3 (TM = 4d elements) for high capacity Na ion batteries

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Abstract

Through comprehensive density functional calculations, we demonstrate oxygen's significant participation in the redox reaction in a Na excess NaxRuO3 cathode material. The availability of O electrons for the redox reaction originates from the local coordination environment. For high sodium content (x ≈ 2), O ions in the layered hexagonal Na2RuO3 compound are coordinated by four Na ions and consequently have their 2p electrons lifted closer to the Fermi level. For lower Na content (x ≈ 1), Na1RuO3 adopts an ilmenite type R[3 with combining macron] structure in which O ions are coordinated by two Ru and two Na ions. In this case, O under-coordination further elevates O 2p states closer to the Fermi level. In both cases, high O electronic population near the Fermi level facilitates continuous participation of O in the redox reaction over a wide range of Na concentrations. Based on this concept, we also predict that Na1NbO3 with an ilmenite framework is a suitable and economical candidate for high voltage and high capacity cathodes for Na ion batteries.

Graphical abstract: Oxygen redox in hexagonal layered NaxTMO3 (TM = 4d elements) for high capacity Na ion batteries

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Publication details

The article was received on 10 Dec 2017, accepted on 22 Jan 2018 and first published on 08 Feb 2018


Article type: Paper
DOI: 10.1039/C7TA10826E
Citation: J. Mater. Chem. A, 2018, Advance Article
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    Oxygen redox in hexagonal layered NaxTMO3 (TM = 4d elements) for high capacity Na ion batteries

    M. H. N. Assadi, M. Okubo, A. Yamada and Y. Tateyama, J. Mater. Chem. A, 2018, Advance Article , DOI: 10.1039/C7TA10826E

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