Liquid-phase synthesis is a promising method for the large-scale production of sulfide-type solid electrolytes. However, solid electrolytes synthesized by liquid-phase methods exhibit lower conductivity values than those synthesized using solid-state synthesis (e.g., mechanical milling). Li₂S-P₂S₅-LiI solid electrolytes are commonly used in all-solid-state battery applications owing to their high ionic conductivity and chemical stability of lithium. Previous studies have shown that Li₂S-P₂S₅-LiI solid electrolytes (Li₂S:P₂S₅:LiI = 3:1:1) synthesized using the liquid-phase method have lower conductivities (0.35–0.63 mS cm⁻¹) than those synthesized via solid-state synthesis (1.35 mS cm⁻¹). The ionic conductivity of Li₂S-P₂S₅-LiI solid electrolytes obtained via liquid-phase synthesis may be improved by optimizing the drying conditions. Our study observed that the Li₂S-P₂S₅-LiI solid electrolytes dried below 130 °C under vacuum and at 170 °C under ambient pressure exhibited an increased ionic conductivity of 1.0 mS cm⁻¹, which is comparable to that of Li₂S-P₂S₅-LiI solid electrolytes obtained via solid-state synthesis. X-ray diffraction patterns revealed that the intensities of the new crystalline phase were higher than those of the Li₄PS₄I phase; in addition, a lower weight loss was observed in the thermogravimetry curve measurements. These results indicated that the drying step at 170 °C under an ambient pressure could promote removal of organic solvent from complex and new phase formation, thereby contributing to improved ionic conductivity. Our study provides important guidance for the optimization of liquid-phase synthesis with the aim of achieving high ionic conductivity.

液相合成是大规模生产硫化物型固体电解质的有前途的方法。然而，通过液相方法合成的固体电解质显示出比使用固态合成（例如，机械研磨）合成的电解质低的电导率值。Li ₂ S-P ₂ S ₅ -LiI固体电解质由于其高离子电导率和锂的化学稳定性而常用于全固态电池应用中。以前的研究表明Li ₂ S-P ₂ S ₅ -LiI固体电解质（Li ₂ S：P ₂ S ₅：LiI = 3：1：1）液相法合成的电导率（0.35-0.63 mS cm ^-1）比固态合成法（1.35 mS cm ^-1）低。可以通过优化干燥条件来改善通过液相合成获得的Li ₂ S-P ₂ S ₅ -LiI固体电解质的离子电导率。我们的研究发现，在真空下于130°C和环境压力下在170°C下干燥的Li ₂ S-P ₂ S ₅ -LiI固体电解质的离子电导率提高了1.0 mS cm ^-1，与Li ₂相当。SP ₂小号₅通过固态合成获得的-LiI固体电解质。X射线衍射图谱表明，新结晶相的强度高于Li ₄ PS ₄ I相的强度。另外，在热重曲线测量中观察到较低的重量损失。这些结果表明，在环境压力下于170°C的干燥步骤可促进有机溶剂从复合物和新相形成中的去除，从而有助于改善离子电导率。我们的研究为实现高离子电导率的目的，为优化液相合成提供了重要的指导。