Rapid Solution Synthesis of Argyrodite-Type Li₆PS₅X (X = Cl, Br, and I) Solid Electrolytes Using Excess Sulfur

All-solid-state lithium-ion batteries (ASSLBs) have the potential to be the next-generation energy storage systems because of their high safety features. However, one of the major challenges to the commercialization of ASSLBs is the development of well-established large-scale manufacturing techniques for solid electrolytes (SEs). Herein, we synthesize Li₆PS₅X (X = Cl, Br, and I) SEs in a total of 4 h by a rapid solution synthesis method using excess elemental sulfur as a solubilizer and reasonable organic solvents. In the system, trisulfur radical anions stabilized by a highly polar solvent increase the solubility and reactivity of the precursor. Raman and UV-vis spectroscopies reveal the solvation behavior of halide ions in the precursor. This result demonstrates that the solvation structure modified by the halide ions determines the chemical stability, solubility, and reactivity of chemical species in the precursor. The prepared Li₆PS₅X (X = Cl, Br, and I) SEs show ionic conductivities of 2.1 × 10^-3, 1.0 × 10^-3, and 3.8 × 10^-6 S cm^-1 at 30 °C, respectively. Our study provides a rapid synthesis of argyrodite-type SEs with high ionic conductivity.