Ion conducting ceramic electrolytes continue to emerge as key components in the advance of electrical energy storage technologies, such as sodium-based batteries. These solid state electrolytes are challenged with providing not only high ionic conductivity, but also serving as a robust physical, electrical, and selective ionic barrier between anolytes and catholytes in these systems. Meeting these requirements means optimizing phase chemistry for selective, facile ion transport while maintaining critical chemical, thermal, and mechanical stability against molten, organic, and potentially aqueous media. Here, we specifically explore a family of NaSICON (Na Super Ion CONducting) separators that may exhibit ionic conductivities greater than 1 mS/cm at room temperature and show excellent chemical stability. We characterize the multi-phasic character of NaSICON, and we discuss how variations in NaSICON microstructure influence both ceramic integrity and ionic conductivity. Meanwhile, strategic changes in NaSICON composition are shown to impact not only ion transport, but also the phase distribution and chemical stability of the ceramic. Critically, these studies reveal strongly interdependent relationships between ceramic composition, structure, and ultimate performance in these complex, functional materials. Learning to manipulate such fundamental materials relationships is key to optimizing stable NaSICON application in advanced ion transport technologies.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.