Jahn-Teller Distortions and Phase Transitions in LiNiO2 Insights from Ab Initio Molecular Dynamics and Variable-Temperature X-ray Diffraction

Jahn-Teller Distortions and Phase Transitions in LiNiO2 : Insights from Ab Initio Molecular Dynamics and Variable-Temperature X-ray Diffraction

© 2024 The Authors. Published by American Chemical Society.

Bibliographische Detailangaben
Veröffentlicht in:Chemistry of materials : a publication of the American Chemical Society. - 1998. - 36(2024), 5 vom: 12. März, Seite 2289-2303
1. Verfasser: Genreith-Schriever, Annalena R (VerfasserIn)
Weitere Verfasser: Alexiu, Alexandra, Phillips, George S, Coates, Chloe S, Nagle-Cocco, Liam A V, Bocarsly, Joshua D, Sayed, Farheen N, Dutton, Siân E, Grey, Clare P
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2024
Zugriff auf das übergeordnete Werk:Chemistry of materials : a publication of the American Chemical Society
Schlagworte:Journal Article
Beschreibung
Zusammenfassung:© 2024 The Authors. Published by American Chemical Society.
The atomistic structure of lithium nickelate (LiNiO2), the parent compound of Ni-rich layered oxide cathodes for Li-ion batteries, continues to elude a comprehensive understanding. The common consensus is that the material exhibits local Jahn-Teller distortions that dynamically reorient, resulting in a time-averaged undistorted R3̅m structure. Through a combination of ab initio molecular dynamics (AIMD) simulations and variable-temperature X-ray diffraction (VT-XRD), we explore Jahn-Teller distortions in LiNiO2 as a function of temperature. Static Jahn-Teller distortions are observed at low temperatures (T < 250 K) via AIMD simulations, followed by a broad phase transition that occurs between 250 and 350 K, leading to a highly dynamic, displacive phase at high temperatures (T > 350 K), which does not show the four short and two long bonds characteristic of local Jahn-Teller distortions. These transitions are followed in the AIMD simulations via abrupt changes in the calculated pair distribution function and the bond-length distortion index and in X-ray diffraction via the monoclinic lattice parameter ratio, amon/bmon, and δ angle, the fit quality of an R3̅m-based structural refinement, and a peak sharpening of the diffraction peaks on heating, consistent with the loss of distorted domains. Between 250 and 350 K, a mixed-phase regime is found via the AIMD simulations where distorted and undistorted domains coexist. The repeated change between the distorted and undistorted states in this mixed-phase regime allows the Jahn-Teller long axes to change direction. These pseudorotations of the Ni-O long axes are a side effect of the onset of the displacive phase transition. Antisite defects, involving Li ions in the Ni layer and Ni ions in the Li layer, are found to pin the undistorted domains at low temperatures, impeding cooperative ordering at a longer length scale
Beschreibung:Date Revised 01.11.2024
published: Electronic-eCollection
Citation Status PubMed-not-MEDLINE
ISSN:0897-4756
DOI:10.1021/acs.chemmater.3c02413