Sodium superionic conduction in Na₂B₁₂H₁₂

Impedance measurements indicate that Na₂B₁₂H₁₂ exhibits dramatic Na⁺ conductivity (on the order of 0.1 S cm⁻¹) above its order-disorder phase-transition at ≈529 K, rivaling that of current, solid-state, ceramic-based, Na-battery electrolytes. Superionicity may be aided by the large size, quasispherical shape, and high rotational mobility of the B₁₂H₁₂²⁻ anions.