Thermal Expansion in Layered Na x MO2

Wataru Kobayashi*, Ayumu Yanagita, Takahiro Akaba, Takahiro Shimono, Daiki Tanabe, Yutaka Moritomo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Layered oxide Na x MO2 (M: transition metal) is a promising cathode material for sodium-ion secondary battery. Crystal structure of O3- and P2-type Na x MO2 with various M against temperature (T) was systematically investigated by synchrotron x-ray diffraction mainly focusing on the T-dependences of a- and c-axis lattice constants (a and c) and z coordinate (z) of oxygen. Using a hard-sphere model with minimum Madelung energy, we confirmed that c/a and z values in O3-type Na x MO2 were reproduced. We further evaluated the thermal expansion coefficients (α a and α c ) along a- and c-axis at 300 K. The anisotropy of the thermal expansion was quantitatively reproduced without adjustable parameters for O3-type Na x MO2. Deviations of z from the model for P2-type Na x MO2 are ascribed to Na vacancies characteristic to the structure.

Original languageEnglish
Article number3988
JournalScientific Reports
Issue number1
Publication statusPublished - 2018 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • General


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