Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.
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 (18)O-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 Mn(4+) 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.
Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Kun
K
Luo
Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Matthew R
MR
Roberts
Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Rong
R
Hao
Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Niccoló
N
Guerrini
School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK.
David M
DM
Pickup
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Yi-Sheng
YS
Liu
Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-75121 Uppsala, Sweden.
Kristina
K
Edström
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Jinghua
J
Guo
School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK.
Alan V
AV
Chadwick
Department of Physics and Astronomy, Division of Molecular and Condensed Matter Physics, Uppsala University, Box 516, S-751 20 Uppsala, Sweden.
Laurent C
LC
Duda
Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Peter G
PG
Bruce