Electrochemical Properties of Li₁₀GeP₂S₁₂ Solid Electrolytes Synthesized Using a Solution-Based Method

Li 10 GeP 2 S 12 is a promising solid electrolyte for solid-state batteries owing to its high ionic conductivity. Although the conventional method of synthesizing Li 10 GeP 2 S 12 in the liquid phase facilitates mass production, the resulting ionic conductivity is inferior to that achieved using mechanical milling. Hence, in this study, Li 10 GeP 2 S 12 was prepared through solution synthesis by incorporating a titanium boat in the heat-treatment step, and the particle characteristics of the synthesized sample were examined. The solution-synthesized sample demonstrated an impressive ionic conductivity of 5.5 mS cm –1, marking the highest value among those obtained from liquid-phase methods to date. Furthermore, the particle size of this sample was smaller than that obtained by mechanical milling. This decrease in particle size was attributed to an increased grain boundary resistance, leading to a diminished total ionic conductivity. X-ray photoelectron spectroscopy revealed the presence of a surface layer on the particles originating from the solvent. This surface layer was identified as one of the factors contributing to a stable interface between Li–In and Li 10 GeP 2 S 12 . These findings imply that adept management of particle characteristic states, including particle size and surface state, is crucial for advancing the development of solid electrolytes with high ionic conductivities and stability toward the anode.