Metal closo-borate compounds grown recent attention as superionic lithium or sodium conductors. In Na2B12H12 or Li2B12H12 the superionic phases are related to the phase transitions at elevated temperatures. Modification of the crystal structure or ion substitution provide the means of tuning their cation conductivity. We report that modifications of Na2B12H12 structure by anion sublattice manipulations or application of the hydrostatic pressure leads to new ionic conductors with conductivity of the order mS/cm at room temperature. The crystal structure, thermodynamic stability and ion dynamics are investigated by the combinations of density functional calculations, X-ray diffraction, spectroscopic and electrochemical experiments. The structure and stability of di-valent metal borates are discussed for magnesium and the first row transition metals. The covalent bonding between Co, Ni and B12H122- anions leads to formation of densely packed crystal structures. The relation between anion packing, crystal structure and ion mobility in metal closo-borate compounds is discussed in frame of DFT calculations combined with diffraction and spectroscopic experiments.

Metal closo-borates as solid-state electrolytes

2019 Spring National Meeting

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