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Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen

DOI: 10.1038/nchem.2471 DOI Help

Authors: Kun Luo (University of Oxford) , Matthew R. Roberts (University of Oxford) , Rong Hao (University of Oxford) , Niccolo Guerrini (University of Oxford) , David Pickup (University of Kent) , Yi-sheng Liu (Advanced Light Source) , Kristina Edström (Uppsala University) , Jinghua Guo (Advanced Light Source) , Alan Chadwick (University of Kent at Canterbury) , Laurent C. Duda (Uppsala University) , Peter Bruce (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Chemistry

State: Published (Approved)
Published: March 2016
Diamond Proposal Number(s): 12635

Abstract: During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of 18O-labelled Li1.2[Ni0.13 2+Co0.13 3+Mn0.54 4+]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13 2+Co0.13 3+Mn0.54 4+]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li+ removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn4+ and Li+ ions, which serve to promote the localization, and not the formation, of true O2 2− (peroxide, O–O ∼1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.

Subject Areas: Energy, Chemistry

Instruments: B18-Core EXAFS

Other Facilities: Advanced Light Source (ALS).