Swirling Spray Flame Synthesis of NASICON-Type Electrolyte Nanoparticles for Solid-State Sodium Batteries

NASICON-type Na₃Zr₂Si₂PO₁₂ (NZSP), as a promising solid electrolyte for all-solid-state sodium batteries, still lacks scalable synthesis method. In this work, NZSP electrolyte nanoparticles are synthesized by swirling spray flame synthesis, and then sintered for dense solid electrolytes by reactive sintering method. NZSP nanoparticles with 2-ethylhexanoic acid (EHA) added have the largest specific surface area (SSA) and smallest size of about 10nm for the gas-to-particle formation route. As-synthesized nanoparticles exhibit a core-shell structure due to distinctive gas-to-solid transformation temperature of different elements. The raw as-synthesized non-NASICON structural nanopowders are then directly molded and sintered to form NASICON crystalline after reactive sintering. EHA added NZSP solid electrolyte with stoichiometric P element amount exhibits the highest ionic conductivity of 0.56 mS / cm at room temperature (25°C), and the conductivity is promoted to 1.4 mS / cm with a little Mg element doped. The excellent electrochemical performance of synthesized solid-state electrolyte nanopowders and the high yield and scalability of swirling spray flame synthesis make it a potential synthesis method to expand the application of NZSP solid electrolyte.