Microwave-Assisted Synthesis of Sulfide Solid Electrolytes for All-Solid-State Sodium Batteries

Sulfide-based solid electrolytes are one of the potential candidates for all-solid-state batteries due to their high ionic conductivity and low synthesis temperature compared to their oxide counterparts. However, the preparation methods involve the requirement of an inert atmosphere for ball milling, heating, and quenching facilities that severely limit their implementation, which necessitates a resurgence of interest in alternate synthesis approaches. Herein, a simple, accelerated, and energy-efficient method for the synthesis of highly crystalline cubic sodium thiophosphate solid electrolyte (Na3PS4) is developed using the microwave-assisted irradiation technique. Along with impedance studies, 23Na solid-state NMR spin-lattice relaxation experiments are performed to obtain insights into Na-ion mobility in Na3PS4 solid electrolytes. The electrochemical properties and the interfacial stability of the electrolyte with the metallic sodium anode are thoroughly investigated and presented in this work. Further, a prototype full-cell constructed using a Na3V2(PO4)3 cathode, a Na3PS4 solid electrolyte, and a modified sodium anode showed promising electrochemical properties. Although numerous studies focus on solid electrolyte interface modification and design, the simple and energy-efficient approach for sodium-ion solid electrolyte synthesis presented here will provide a meaningful advance to the accelerated synthesis of sulfide electrolyte-based all-solid-state batteries.