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Superionic Conduction in Co‐Vacant P2‐NaxCoO2 Created by Hydrogen Reductive Elimination |
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| Authors: | Dr. Kenichi Kato Dr. Hidetaka Kasai Dr. Akihiro Hori Prof. Dr. Masaki Takata Prof. Dr. Hiroshi Tanaka Prof. Dr. Susumu Kitagawa Akira Kobayashi Dr. Nobuki Ozawa Prof. Dr. Momoji Kubo Dr. Hidekazu Arikawa Prof. Dr. Tatsuya Takeguchi Dr. Masaaki Sadakiyo Prof. Dr. Miho Yamauchi |
| Affiliation: | 1. RIKEN SPring-8 Center, Sayo-gun, Hyogo, Japan;2. CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan;3. Faculty of Pure and Applied Sciences, TIMS, CiRfSE, University of Tsukuba, Tsukuba, Ibaraki, Japan;4. Institute for Integrated Cell-Material Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto, Japan;5. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan;6. Department of Materials Science, Shimane University, Japan;7. Graduate School of Engineering, Tohoku University, Sendai, Japan;8. Institute for Materials Research, Tohoku University, Sendai, Japan;9. Department of Chemistry and Bioengineering, Iwate University, Iwate, Japan;10. International Institute for Carbon-Neutral Energy Research, Kyushu University, Fukuoka, Japan |
| Abstract: | The layered P2‐NaxMO2 (M: transition metal) system has been widely recognized as electronic or mixed conductor. Here, we demonstrate that Co vacancies in P2‐NaxCoO2 created by hydrogen reductive elimination lead to an ionic conductivity of 0.045 S cm?1 at 25 °C. Using in situ synchrotron X‐ray powder diffraction and Raman spectroscopy, the composition of the superionic conduction phase is evaluated to be Na0.61(H3O)0.18Co0.93O2. Electromotive force measurements as well as molecular dynamics simulations indicate that the ion conducting species is proton rather than hydroxide ion. The fact that the Co‐stoichiometric compound Nax(H3O)yCoO2 does not exhibit any significant ionic conductivity proves that Co vacancies are essential for the occurrence of superionic conductivity. |
| Keywords: | layered compounds molecular dynamics reductive elimination superionic conductivity X-ray diffraction |