LAUSR

Abstract Na based all-solid-state batteries are one of the most promising candidates for large-scale electrochemical energy storage owing to their low cost and outstanding safety properties. The key enabler of this technology is solid electrolyte with sufficiently high ionic conductivity at room temperature. In this work, the design, synthesis, characterization, and testing of a series of novel fast Na-ion conductors, Na4-x-ySn1-xAxS4-yXy with aliovalent cation (P5+/Sb5+) and anion (Cl−/Br−) substitutions of the parent compound Na4SnS4 are reported. The doped samples crystalize in a new phase with space group I41/acd and show ionic conductivities that are one to four orders of magnitude higher than that of undoped Na4SnS4. R. t. conductivity of 0.64 mS cm−1 is achieved in Na3.7Sn0.8Sb0.2S3.9Cl0.1 with a low activation energy of 0.26 eV. Rietveld refinement against high resolution synchrotron X-ray powder diffraction data reveals that the distribution of the doping ions and the resulted Na vacancies are underlying causes of the enhanced conductivity.