Sodium ionic conduction in complex hydrides with [BH4]− and [NH2]− anions

We report the experimental results of structural and sodium ionic conductive properties of the Na(BH4)–Na(NH2)–NaI system. Na(BH4)0.5(NH2)0.5 with [BH4]− and [NH2]− complex anions formed by combining Na(BH4) and Na(NH2) complex hydrides shows the most superior sodium ionic conductivity of 2 × 10−6 S/cm at 300 K because of the specific antiperovskite-type structure with vacancies in the Na+ site Furthermore, Na(BH4)0.5(NH2)0.5 shows a high electrochemical stability of at least 6 V (vs Na+/Na). The result suggests that Na(BH4)0.5(NH2)0.5 could be a potential candidate for solid electrolyte.