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

DOI: 10.1038/nchem.2923

Authors: Urmimala Maitra (University of Oxford) , Robert A. House (University of Oxford) , James W. Somerville (University of Oxford) , Nuria Tapia-Ruiz (University of Oxford) , Juan G. Lozano (University of Oxford) , Niccolo Guerrini (University of Oxford) , Rong Hao (University of Oxford) , Kun Luo (University of Oxford) , Liyu Jin (University of Oxford) , Miguel A. Pérez-Osorio (University of Oxford) , Felix Massel (Uppsala University) , David M. Pickup (University of Kent) , Silvia Ramos (University of Kent) , Xingye Lu (Swiss Light Source) , Daniel E. Mcnally (Swiss Light Source) , Alan V. Chadwick (University of Kent) , Feliciano Giustino (University of Oxford) , Thorsten Schmitt (Swiss Light Source) , Laurent C. Duda (Uppsala University) , Matthew R. Roberts (University of Oxford) , Peter G. Bruce (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Chemistry , VOL 10 , PAGES 288 - 295

State: Published (Approved)
Published: January 2018
Diamond Proposal Number(s): 12559

Abstract: The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds to have promise as a new class of high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion charge compensated by the transition-metal ions. The additional capacity is provided through charge compensation by oxygen-redox chemistry and some oxygen loss. It has been reported previously that O-redox occurs in O-2p orbitals that interact with alkali-ions in the transition-metal and alkali-ion layers (i.e. O-redox occurs in compounds containing Li+ - O2p - Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits excess capacity; here we show this is also due to O-redox, despite Mg2+ residing in the transition-metal (TM) layers rather than alkali-metal ions, demonstrating that excess alkali-metal ions are not required to activate O-redox. We also show that unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose O. Extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen promoting oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2 stabilising oxygen.

Journal Keywords: Batteries

Diamond Keywords: Batteries; Sodium-ion

Subject Areas: Materials, Chemistry, Energy


Instruments: B18-Core EXAFS

Other Facilities: ADRESS at Swiss Light Source

Added On: 24/03/2018 15:28

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science Chemical Engineering Engineering & Technology

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) X-ray Absorption Near Edge Structure (XANES)