Novel production process for lithium sulfide from lithium hydroxide by reacting with hydrogen sulfide gas generated from iron sulfide

The efficient production of lithium sulfide (Li₂S), a key raw material for sulfide electrolytes in all-solid-state batteries, is important owing to its high cost. In this study, an efficient method for producing high-purity Li₂S by the reaction between lithium hydroxide (LiOH) and hydrogen sulfide (H₂S) gas was investigated. The study used H₂S gas generated from the dissolution of iron sulfide (FeS) in a sulfuric acid (H₂SO₄) solution at 298 K. When reactions between LiOH and the generated H₂S gas were performed at 373–673 K for 1 h, Li₂S was obtained. Notably, the generation of sulfur was observed when the reaction temperature was above 573 K. Based on the experimental results and thermodynamic analysis, the principle of Li₂S production by the reaction of LiOH with H₂S gas is described. This study suggests the feasibility of the direct production of Li₂S from LiOH by reacting H₂S gas and the utilization of FeS as a source of H₂S gas to reduce its environmental impact.