Oxygen-redox activity in non-Li-excess W-doped LiNiO2 cathode


The desire to increase the energy density of stoichiometric layered LiTMO2 (TM = 3d transition metal) cathode materials has promoted investigation into their properties at high states of charge. Although there is increasing evidence for pronounced oxygen participation in the charge compensation mechanism, questions remain whether this is true O-redox, as observed in Li-excess cathodes. Through a high-resolution O K-edge resonant inelastic X-ray spectroscopy (RIXS) study of the Mn-free Ni-rich layered oxide, LiNi0.98W0.02O2, we demonstrate that the same oxidized oxygen environment exists in both Li-excess and non-Li-excess systems. The observation of identical RIXS loss features in both classes of compounds is remarkable given the differences in their crystallographic structure and delithiation pathways. This lack of a specific structural motif reveals the importance of electron correlation in the charge compensation mechanism for these systems and indicates how a better description of charge compensation in layered oxides is required to understand anionic redox for energy storage.

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Supplementary material

Oxygen-redox activity in non-Li-excess W-doped LiNiO2 cathode
Experimental details, XRD analysis of pristine WLNO, X-ray absorption spectroscopy of WLNO, Pawley analysis of ex situ XRD data of cycled electrodes, Soft XAS data of WLNO electrodes, HAXPES data, High resolution RIXS data