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Issue 8, 2018
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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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Article information


Submitted
10 Dec 2017
Accepted
22 Jan 2018
First published
08 Feb 2018

J. Mater. Chem. A, 2018,6, 3747-3753
Article type
Paper

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, 6, 3747
DOI: 10.1039/C7TA10826E

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