Na3-xEr1-xZrxCl6-A Halide-Based Fast Sodium-Ion Conductor with Vacancy-Driven Ionic Transport

Driven by the rising demand for consumer electronics, the field of all solid-state batteries employing solid electrolytes as the ion-conducting separator has attracted enormous attention in the last years. Recently, the lithium-conducting rare-earth halides A(3)MX(6) (A = Li, M = Y, Er, X = CI, Br, I) and Li3InX6 have been rediscovered as potential solid electrolytes, showing a good overall electrochemical performance, while the corresponding sodium-based compounds have been mostly overlooked yet. Here, we report the ionic transport properties of the Na-ion conducting rare-earth halide solid electrolyte Na3-xEr1-xZrxCl6. Na3-xEr1-xZrxCl6 shows a conductivity enhancement from 10(-9) S.cm(-1) up to of similar to 0.04 mS.cm(-1) for Na2.4Er0.4Zr0.6Cl6, alongside interesting local structural rearrangements of the polyhedral motifs along the series of solid solutions. This series of halide-based sodium-ion conductors sheds light on promising compositions in search for superionic materials.