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Sodium Superionic Conduction in Na2B12H12

Published

Author(s)

Terrence J. Udovic, Matoaki Matsuo, Atsushi Unemoto, Kristina Verdal, Vitalie Stavila, Alexander V. Skripov, John J. Rush, Hitoshi Takamura, Shin-Ichi Orimo

Abstract

The need for cheaper, Li-free battery technologies has prompted the search for new Na-ion-based electrolyte materials. One such material, Na2B12H12, undergoes an entropy-driven transition upon heating from an ordered monoclinic structure to a disordered cubic structure at around 529 K. Impedance measurements across the phase transition have indicated a nearly three-orders-of-magnitude jump in Na+ cation conductivity, approaching 0.1 S/cm. The unusually high cation mobility above the transition is a result of the "melting" of the Na+ cation sublattice within the body-centered-cubic (bcc)arrangement of the orientationally disordered B12H122- anions, similar to what is observed for the mobile Ag+ sublattice in the bcc phase of AgI. The high reorientational mobility, relatively large size, and quasispherical shape of the B12H122- anions may all play roles in facilitating Na+ diffusion. Superionicity, high-temperature stability, and low cost combine to make Na2B12H12 an attractive solid-state electrolyte for future Na-based batteries. It is probably that even better properties, i.e., lower phase-transition temperatures and higher ion conduction, can be realized, eg.g., via modification or subsitiution of the B12H122+ anions.
Citation
Chemical Communications
Volume
50

Keywords

battery, cation vacancy, complex hydride, conductivity, impedance measurement, ion conductivity, Na cation, sodium, superionicity

Citation

Udovic, T. , Matsuo, M. , Unemoto, A. , , K. , Stavila, V. , , A. , , J. , Takamura, H. and Orimo, S. (2014), Sodium Superionic Conduction in Na<sub>2</sub>B<sub>12</sub>H<sub>12</sub>, Chemical Communications, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915272 (Accessed July 27, 2021)
Created April 11, 2014, Updated February 19, 2017