Rethinking Oxygen Redox: Does Oxygen Dimerisation Occur without Oxidation in Li2NiO3?

19 June 2024, Version 1

Abstract

In layered lithium transition metal oxide cathodes, high voltage operation is accompanied by the formation of oxygen dimers, which are widely used as an indicator of oxygen-redox activity. However, understanding the role that oxygen dimerisation plays in facilitating charge compensation is still needed. Here, Li2NiO3 (a 3d8L2-containing compound, where L is a ligand hole) is studied as a model system, where oxygen dimerisation is shown to occur without cathode oxidation. Electrochemical cycling results in a net reduction of the cathode structure, accompanied by structural transformations, despite spectroscopic features of oxygen dimers arising at the top of charge. Oxygen dimerisation is shown to coexist alongside a structurally transformed and electronically reduced cathode structure, thus raising questions about its origin with respect to delithiation.

Keywords

Oxygen-Redox
Oxygen Dimerisation
Ligand Holes
Ni-rich Cathodes
XAS
RIXS

Supplementary materials

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Description
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Supporting Information
Description
Experimental Details, Supplementary Datasets, Fitting Parameters
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