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Lithium sulfide (Li2S) nanocrystals (NCs) arecritical materials for emerging solid-state and Li?S batterytechnologies. Conventional synthesis is energy intensive andcostly, and offers limited size control. Here we describe ascalable approach wherein Li2S is formed by contactinghydrogen sulfide (H2S) gas with metalorganic solution atambient temperature. NCs are recovered with essentially100% yield in a subsequent evaporation step. Control of NCsize and uniformity is demonstrated through manipulatingparameters such as precursor concentration and solventevaporation rate. A suite of complementary techniquesconfirm the production of anhydrous, phase-pure Li2Snanocrystals with tunable size (5?20 nm) and narrow particlesize distributions. Mild annealing conditions are identified to provide the purity necessary for battery applications, whileretaining 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.