Oxygen-Redox Activity in Non-Lithium-Excess Tungsten-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.Received 21 October 2022Revised 7 February 2023Accepted 21 February 2023DOI:https://doi.org/10.1103/PRXEnergy.2.013005Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectrochemical propertiesMixed ionic electronic conductionPhysical SystemsEnergy applicationsEnergy materialsTechniquesX-ray absorption spectroscopyX-ray diffractionX-ray emission spectroscopyEnergy Science & TechnologyCondensed Matter, Materials & Applied Physics