Issue 8, 2018

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

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

Supplementary files

Article information

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

J. Mater. Chem. A, 2018,6, 3747-3753

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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