Synthesis of Deliquescent Lithium Sulfide in Air

Making the Unfeasible Feasible: Synthesis of the Battery Material Lithium Sulfide via the Metathetic Reaction between Lithium Sulfate and Sodium Sulfide

Lithium sulfide (Li2S) is a highly desired material for advanced batteries. However, its current industrial production is not suitable for large-scale applications in the long run because the process is carbon-emissive, energy-intensive, and cost-ineffective. This article demonstrates a new method that can overcome these challenges by reacting lithium sulfate (Li2SO4) with sodium sulfide. This approach, which seems unfeasible initially because Li2SO4 is barely soluble in ethanol at room temperature, becomes feasible when heated ethanol and an excess amount of Li2SO4 are used. More interestingly, product purification is easier than that in other metathetic reactions, thanks to the poor solubility of Li2SO4. In order to further minimize the overall costs of producing Li2S, the concomitant byproduct LiNaSO4 and the unfinished precursor Li2SO4 are converted into more valuable materials, Li2CO3 and Na2SO4. Moreover, the homemade Li2S is competitive with the commercial Li2S in cathode performance and gains further enhancement when being composited with the Co9S8 catalyst. Thus, this Li2SO4-based metathesis of Li2S has great potential for practical applications.