Strong oxygen participation in the redox governing the structural and electrochemical properties of Na-rich layered oxide Na2IrO3

Arnaud J. Perez, Dmitry Batuk, Matthieu Saubanère, Gwenaelle Rousse, Dominique Foix, Eric McCalla, Erik J. Berg, Romain Dugas, Karel H.W. Van Den Bos, Marie Liesse Doublet, Danielle Gonbeau, Artem M. Abakumov, Gustaaf Van Tendeloo, Jean Marie Tarascon

Research output: Contribution to journalArticlepeer-review

97 Citations (Scopus)

Abstract

The recent revival of the Na-ion battery concept has prompted intense activities in the search for new Na-based layered oxide positive electrodes. The largest capacity to date was obtained for a Na-deficient layered oxide that relies on cationic redox processes only. To go beyond this limit, we decided to chemically manipulate these Na-based layered compounds in a way to trigger the participation of the anionic network. We herein report the electrochemical properties of a Na-rich phase Na2IrO3, which can reversibly cycle 1.5 Na+ per formula unit while not suffering from oxygen release nor cationic migrations. Such large capacities, as deduced by complementary XPS, X-ray/neutron diffraction and transmission electron microscopy measurements, arise from cumulative cationic and anionic redox processes occurring simultaneously at potentials as low as 2.7 V vs Na+/Na. The inability to remove more than 1.5 Na+ is rooted in the formation of an O1-type phase having highly stabilized Na sites as confirmed by DFT calculations, which could rationalize as well the competing metal/oxygen redox processes in Na2IrO3. This work will help to define the most fertile directions in the search for novel high energy Na-rich materials based on more sustainable elements than Ir.

Original languageEnglish
Pages (from-to)8278-8288
Number of pages11
JournalChemistry of Materials
Volume28
Issue number22
DOIs
Publication statusPublished - 22 Nov 2016

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