Optimization of Crystallization Conditions and Electrochemical Studies of Na ₅ YSi ₄ O ₁₂ Glass-Ceramic Electrolytes

Glass-ceramic synthesis allows for a faster, scalable, and facile fabrication procedure of ceramic electrolytes in a wide variety of shapes and thicknesses. Na5YSi4O12 glass-ceramic electrolytes have shown promising electrochemical performance, exhibiting ionic conductivities in the range of 10–4∼10–3 S cm–1. However, all previous studies used short crystallization durations to minimize sodium loss. While short sintering durations usually limit sodium loss by evaporation or volatilization, it may also be inadequate to crystallize the entirety of glass to pure Na5YSi4O12 glass-ceramic. Crystallization of purely Na5YSi4O12 glass-ceramic has not been reported or optimized previously. In this study, the crystallization of Na2O–Y2O3–Si2O glass was systematically investigated by X-ray diffraction measurements and Rietveld refinement. We obtained a glass-ceramic composition purely of Na5YSi4O12. This glass-ceramic exhibited a relative density of 98.98%. Electrochemical impedance spectroscopic (EIS) analysis showed a total ionic conductivity of 1.15 × 10–3 S cm–1, which was significantly higher than the total ionic conductivity of the Na5YSi4O12 electrolyte prepared with solid-state reaction (1.5 × 10–4 S cm–1) by our group, previously. Further electrochemical studies were performed to test the electrochemical stability window, electronic conductivity, critical current density, and plating/stripping performance. The glass-ceramic electrolyte lasted noticeably longer than the electrolyte prepared by solid-state reaction in galvanostatic plating/stripping at 15 μA cm–2 current density without short-circuiting.