Ionic conduction in ammonia functionalised -dodecaborates MBHNH (M = Li and Na).

Metal hydroborates and their derivatives have been receiving attention as potential solid-state ion conductors for battery applications owing to their impressive electrochemical and mechanical characteristics. However, to date only a fraction of these compounds has been investigated as solid-state electrolytes. Here, MBHNH (M = Li and Na) hydroborates are synthesized and investigated as electrolyte materials for all-solid-state batteries. The room temperature α-NaBHNH was structurally solved in 222 ( = 7.1972(3) Å, = 9.9225(4) Å, and = 14.5556(5) Å). It shows a polymorphic structural transition near 140 °C to cubic 3̄. LiBHNH and NaBHNH exhibit cationic conductivities of (Li) = 3.0 × 10 S cm and (Na) = 1.2 × 10 S cm at 200 °C. Hydration is found to improve ionic conductivity of the hydroborates. It is presumed that modest ionic conductivities could be due to a lack of significant re-orientational dynamics in the crystal structure resulting from the presence of the bulky -NH group in the anion.