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Superionic Conduction in Co‐Vacant P2‐Na x CoO 2 Created by Hydrogen Reductive Elimination
Author(s) -
Kato Kenichi,
Kasai Hidetaka,
Hori Akihiro,
Takata Masaki,
Tanaka Hiroshi,
Kitagawa Susumu,
Kobayashi Akira,
Ozawa Nobuki,
Kubo Momoji,
Arikawa Hidekazu,
Takeguchi Tatsuya,
Sadakiyo Masaaki,
Yamauchi Miho
Publication year - 2016
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201600370
Subject(s) - electromotive force , ionic conductivity , fast ion conductor , conductivity , stoichiometry , raman spectroscopy , ionic bonding , chemistry , hydrogen , ion , analytical chemistry (journal) , hydroxide , inorganic chemistry , phase (matter) , thermal conduction , crystallography , materials science , electrolyte , electrode , physics , organic chemistry , quantum mechanics , chromatography , optics , composite material
The layered P2‐Na x MO 2 (M: transition metal) system has been widely recognized as electronic or mixed conductor. Here, we demonstrate that Co vacancies in P2‐Na x CoO 2 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 Na 0.61 (H 3 O) 0.18 Co 0.93 O 2 . 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 Na x (H 3 O) y CoO 2 does not exhibit any significant ionic conductivity proves that Co vacancies are essential for the occurrence of superionic conductivity.