Evidence for bond-disproportionation in LiNiO2 from x-ray absorption spectroscopy

R. J. Green; H. Wadati; T. Z. Regier; A. J. Achkar; C. McMahon; J. P. Clancy; H. A. Dabkowska; B. D. Gaulin; G. A. Sawatzky; D. G. Hawthorn

arXiv · 2011.06441

Evidence for bond-disproportionation in LiNiO2 from x-ray absorption spectroscopy

R. J. Green·H. Wadati·T. Z. Regier·A. J. Achkar·C. McMahon·J. P. Clancy·H. A. Dabkowska·B. D. Gaulin·G. A. Sawatzky·D. G. Hawthorn

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Abstract

The electronic structure of LiNiO$_2$, a promising Li-ion battery cathode material, has remained a challenge to understand due to its highly covalent yet correlated nature. Here we elucidate the electronic structure in LiNiO$_2$ and the related compound NaNiO$_2$ using x-ray absorption spectra (XAS) and quantum many-body calculations. Notably, we use inverse partial fluorescence yield to correctly measure the Ni $L$-edge XAS, which is inaccurate using conventional methods. We show that the XAS are indicative of a strong Jahn-Teller effect in NaNiO$_2$ and a bond disproportionated state in LiNiO$_2$, supporting a theory of a high-entropy, glassy disproportionated state that stabilizes charging cycles in LiNiO$_2$.

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R. J. Green, H. Wadati, T. Z. Regier, A. J. Achkar, C. McMahon, J. P. Clancy, H. A. Dabkowska, B. D. Gaulin, G. A. Sawatzky, D. G. Hawthorn. 2020-11-12. Evidence for bond-disproportionation in LiNiO2 from x-ray absorption spectroscopy. https://arxiv.org/abs/2011.06441

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