Structural Elucidation of Na 2/3 NiO 2 , a Dynamically Stabilized Cathode Phase with Nickel Charge and Sodium Vacancy Ordering

作者：J. Steele, Annalena R. Genreith‐Schriever, Joshua D. Bocarsly, Liam A. V. Nagle‐Cocco, Farheen N. Sayed, Marie Juramy, Christopher A. O’Keefe, Fabio Orlandi, Pascal Manuel, Siân E. Dutton, Clare P. Grey · 发表于：Chemistry of Materials · 年份：2025 · DOI：10.1021/acs.chemmater.5c00084 · 被引用次数：8 · 研究领域：Ferroelectric and Piezoelectric Materials、Advancements in Battery Materials、Advanced Battery Materials and Technologies

High Resolution Image Download MS PowerPoint Slide NaNiO 2 (NNO) has been investigated as a promising sodium-ion battery cathode material, but it is limited by degradation-induced capacity fade. On desodiation, NNO forms multiple phases with large superstructures due in part to Na + -ion vacancy ordering; however, their structures are unknown. Here, we report a structural solution to the Na 2/3 NiO 2 (P ′ 3) desodiated phase using combined Rietveld refinement of high-resolution synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) data, magnetic susceptibility, and 23 Na solid-state nuclear magnetic resonance (ssNMR) spectroscopy. Our experimental results are compared to ab initio molecular dynamics (AIMD) simulations, which indicate multiple low-energy structures that are dynamically populated. We observe a combination of competing effects that contribute to the resultant dynamic nature of the structure, including honeycomb ordering of mixed-valence Ni, orbital ordering of Jahn–Teller (JT) distorted Ni 3+, and zigzag Na + /vacancy ordering. Our work provides evidence of multiple contributions to the structures of desodiated Na 2/3 NiO 2, along with a framework for investigating the other unsolved desodiated structures. This work may also inform our understanding of the Jahn–Teller evolution in other nickel-rich lithium- and sodium-ion cathodes, such as LiNiO 2 .