Tetragonal Na3SbS4 is synthesized as a new sodium superionic conductor. The discovery of Na vacancies experimentally verifies previous theoretical predictions. Na vacancies, distorted cubic sulphur sublattices and large Na atomic displacement parameters lead to the ionic conductivity as high as 3 mS cm-1, a value significantly higher than those of state-of-the-art sodium sulfide electrolytes.
Keywords: chalcogenide; sodium batteries; sodium superionic conductors; solid electrolytes; sulfides.