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  • Oxygen redox chemistry Na0.67Mg0.28Mn0.72O2_NatureChem

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Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2

Research output: Contribution to journalJournal articlepeer-review

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  • Urmimala Maitra
  • Robert H House
  • James W. Somerville
  • Nuria Tapia-Ruiz
  • Juan G. Lozano
  • Niccoló Guerrini
  • Rong Hao
  • Kun Luo
  • Liyue Jing
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<mark>Journal publication date</mark>22/01/2018
<mark>Journal</mark>Nature Chemistry
Volume10
Number of pages8
Pages (from-to)288-295
Publication StatusPublished
<mark>Original language</mark>English

Abstract

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li+–O(2p)–Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2, which stabilizes oxygen.

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© 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.