Scalable Synthesis of Size-Controlled Li₂S Nanocrystals for Next-Generation Battery Technologies

Abstract

Lithium sulfide (Li2S) nanocrystals (NCs) are critical materials for emerging solid-state and Li–S battery technologies. Conventional synthesis is energy intensive and costly, and offers limited size control. Here we describe a scalable approach wherein Li2S is formed by contacting hydrogen sulfide (H2S) gas with metalorganic solution at ambient temperature. NCs are recovered with essentially 100% yield in a subsequent evaporation step. Control of NC size and uniformity is demonstrated through manipulating parameters such as precursor concentration and solvent evaporation rate. A suite of complementary techniques confirm the production of anhydrous, phase-pure Li2S nanocrystals with tunable size (5–20 nm) and narrow particle size distributions. Mild annealing conditions are identified to provide the purity necessary for battery applications, while retaining the original size distribution. Simple cathodes fabricated from the resulting NCs show promising battery performance, where the capacity approaches the theoretical value and displays good cyclability and rate capability.