On the Origin of the Non-Arrhenius Na-ion Conductivity in Na 3 OBr

• Published in: Angewandte Chemie 2023-12, Vol.135 (51), p.e202314444
• Main Authors: Darminto, Brigita, Rees, Gregory J, Cattermull, John, Hashi, Kenjiro, Diaz-Lopez, Maria, Kuwata, Naoaki, Turrell, Stephen J, Milan, Emily, Chart, Yvonne, Di Mino, Camilla, Jeong Lee, Hyeon, Goodwin, Andrew L, Pasta, Mauro
• Format: Article
• Language: English
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202314444

The sodium-rich antiperovskites (NaRAPs) with composition Na OB (B=Br, Cl, I, BH , etc.) are a family of materials that has recently attracted great interest for application as solid electrolytes in sodium metal batteries. Non-Arrhenius ionic conductivities have been reported for these materials, the origin of which is poorly understood. In this work, we combined temperature-resolved bulk and local characterisation methods to gain an insight into the origin of this unusual behaviour using Na OBr as a model system. We first excluded crystallographic disorder on the anion sites as the cause of the change in activation energy; then identified the presence of a poorly crystalline impurities, not detectable by XRD, and elucidated their effect on ionic conductivity. These findings improve understanding of the processing-structure-properties relationships pertaining to NaRAPs and highlight the need to determine these relationships in other materials systems, which will accelerate the development of high-performance solid electrolytes.