Abstract
All-solid-state sodium batteries (ASSSBs) are promising candidates for grid-scale energy storage applications. To date, however, there are no commercialized ASSSBs due in part to the lack of a solid electrolyte (SE) that meets all of the requirements of low cost, facile fabrication, high Na+ conductivity, electrochemical stability, and is resistant to sodium metal dendrite penetration. In this work, we report a family of oxysulfide glass SEs (Na3PS4−xOx, where 0 < x ≤ 0.6) that combine the advantages of sulfides and oxides, we demonstrate stable electrochemical cycling of Na metal for hundreds of hours and the highest critical current density of 2.3 mA cm−2 among all Na-ion conducting sulfide-based SEs. These performance enhancements are found to be associated with the ability of the oxysulfide glass to undergo room temperature pressure induced amorphization that creates a fully homogeneous glass structure that has robust mechanics and substantial chemical and electrochemical stability. Microstructural analysis revealed that the added oxygen creates a glassy network structure by forming bridging oxygen units resulting in a significantly stronger defect-free glass network and two orders of magnitude lower electronic conductivity compared to the fully ionic and non-network structure of Na3PS4. We show ambient-temperature sodium-sulfur batteries (ATSSBs) can be fabricated from these SEs that demonstrate the highest specific energy among the current sodium batteries. The unique room-temperature processing of composite SE structures may provide a sustainable path forward for the further development of ATSSBs in particular and ASSSBs in general.
An electrochemically stable defect-free glassy electrolyte formed at room temperature for all-solid-state sodium batteries