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Fast Sodium Ionic Conduction in Na2B10H10-Na2B12H12 Pseudo-Binary Complex Hydride and Application to a Bulk-Type All-Solid-State Battery



Koji Yoshida, Toyoto Sato, Atsushi Unemoto, Motoaki Matsuo, Tamio Ikeshoji, Terrence J. Udovic, Shin-Ichi Orimo


In the present work, we developed highly ion-conductive Na2B10H10-Na2B12H12 closo-borane (solid-solution) salts via mechanically ball-milling admixtures of the pure Na2B10H10 and Na2B12H12 components. They were characterized by XRD, Raman spectroscopy, and ionic conductivity measurements, and their performance as an electrolyte was tested in a prototype all-solid-state sodium battery. These closo-borane salt mixtures displayed the partial stabilization of highly ion-conductive, disordered cubic phases at room temperature, whosevolume fraction and favored structural symmetry (body-centered cubi or face-centered) depended on the milling conditions and molar ratio of the component compounds. First-principles molecular-dynamics simulations demonstrated that the total energy of the closoborane salt mixtures and pure materials are quite close, which may help to explain the observed stabilization of the mixed compounds. The ionic conductivity of the closo-borane salt mixture was correlated with the fraction of the disordered cubic phase present. It was maximized at a 1:3 molar ratio with a conductivity as high as 3x10-4 S cm-1 at 303 K, which is approximately 2-3 orders of magnitude higher than either pure material. An all-solid-state sodium ion battery with a closo-borane-mixture electrolyte successfully demonstrated a stable discharge/charge cycle for at least ten cycles, with a high active-material utilization ratio.
Applied Physics Letters


all-solid-state batteries, conductivity, closo-boranes, ionic conductivity, salt mixtures, sodium ion batteries, sodium closo-boranes, solid solutions, X-ray diffraction


Yoshida, K. , Sato, T. , Unemoto, A. , Matsuo, M. , Ikeshoji, T. , Udovic, T. and Orimo, S. (2017), Fast Sodium Ionic Conduction in Na<sub>2</sub>B<sub>10</sub>H<sub>10</sub>-Na<sub>2</sub>B<sub>12</sub>H<sub>12</sub> Pseudo-Binary Complex Hydride and Application to a Bulk-Type All-Solid-State Battery, Applied Physics Letters, [online], (Accessed April 21, 2024)
Created March 5, 2017, Updated October 12, 2021