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

paper

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

arXiv:2011.06441

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 $_{2}$ .

5 pages, 3 figures