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Stacking Disorders in MixedAlkali Honeycomb Layered Oxide NaKNi2TeO6 and Feasibility for Mixed-Cation Transport

revised on 30.03.2021, 04:18 and posted on 30.03.2021, 08:57 by Titus Masese, Yoshinobu Miyazaki, Josef Rizell, Godwill Mbiti Kanyolo, Chih-Yao Chen, Hiroki Ubukata, Keigo Kubota, Kartik Sau, Tamio Ikeshoji, Zhen-Dong Huang, Kazuki Yoshii, Teruo Takahashi, Miyu Ito, Hiroshi Senoh, Jinkwang Hwang, Abbas Alshehabi, Kazuhiko Matsumoto, Masatomo Yashima, Kotaro Fujii, Toshiyuki Matsunaga, Masahiro Shikano, Yoshiharu Uchimoto, Cedric Tassel, Rika Hagiwara, Hiroshi Kageyama, Tomohiro Saito
We demonstrate the feasibility of using a combination of alkali atoms (Na and K) to develop a robust mixed-alkali honeycomb layered oxide NaKNi2TeO6. Through a series of atomic-resolution transmission electron microscopy in multiple zone axes, we reveal for the first time the local atomic structural disorders characterised by aperiodic stackings and incoherency in the alternating arrangement of Na and K atoms. Our findings indicate great structural versatility that renders NaKNi2TeO6 an ideal platform for investigating other fascinating properties such as mixed ionic transport and intriguing electromagnetic and quantum phenomena amongst honeycomb layered oxides. Finally, we unveil the possibility of inducing mixed Na- and K-ion transport electrochemistry of NaKNi2TeO6 at high voltages (~ 4V), thus epitomising it as a competent cathode candidate for the emerging dendrite-free batteries based on NaK liquid metal alloy as anodes. The results not only betoken a new avenue for developing functional materials with fascinating crystal versatility, but also prefigure a new age of ‘dendrite-free’ energy storage system designs that rely on mixed-cation electrochemistry.


National Institute of Advanced Industrial Science and Technology (AIST)

Japan Prize Foundation

Japan Society for the Promotion of Science (JSPS KAKENHI Grant Numbers 19 K15685, JP19H00821 and JP20K05086)

TEPCO Memorial Foundation


Email Address of Submitting Author


National Institute of Advanced Industrial Science and Technology (AIST)



ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of interest