Possible high-potential ilmenite type N a1M O3 (M= V-Ni) cathodes realized by dominant oxygen redox reaction POSSIBLE HIGH-POTENTIAL ILMENITE TYPE ... ASSADI, OKUBO, YAMADA, and TATEYAMA

M. H.N. Assadi, Masashi Okubo, Atsuo Yamada, Yoshitaka Tateyama

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1 Citation (Scopus)

Abstract

Identifying high-voltage cathode materials is critically important for increasing the energy density of Na ion batteries. Through a comprehensive density-functional survey, we demonstrate that oxygen redox in R3 (ilmenite structure) Na1MO3 generates high operating voltage upon extraction and insertion of a Na ion. In the R3 structure, O ions are undercoordinated by two M and two Na ions and two vacant sites, creating unhybridized O 2p states with a nonbonding character that are lifted closer to the Fermi level. Since O 2p and M t2g states do not significantly overlap at the top of the valence band, the redox reaction is mainly borne on O ions. We also show that, in general, higher covalent bonding between the transition metal and oxygen results in higher voltage in this class of materials in which O redox is dominant. Furthermore, a thorough examination of the phase stability of R3 Na1MO3 compounds reveals that Na1VO3 is an economical high-voltage (5.907 V) cathode with robust cyclability for Na ion batteries. Finally, although the crystal overlap Hamilton population does not indicate any significant bonding between oxidized O ions upon desodiation in NaxMO3 compounds, we predict that gaseous O2 may still develop through thermodynamic decomposition of Na1MO3 to Na1MO2 in some compounds.

Original languageEnglish
Article number015401
JournalPhysical Review Materials
Volume4
Issue number1
DOIs
Publication statusPublished - 2020 Jan 2
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

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