Sodium Superionic Conduction in Na2B12H12

Published

April 11, 2014

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 B₁₂H₁₂^2- 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 B₁₂H₁₂^2- 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

Pub Type

Journals

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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. , Kasianowicz, J. , Takamura, H. and Orimo, S. (2014), Sodium Superionic Conduction in Na₂B₁₂H₁₂, Chemical Communications, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915272 (Accessed September 18, 2024)