Paper MS-MoM5
Efficient Manufacturing of Nano-structured Lithium Sulfide for Next Generation Batteries
Monday, November 7, 2016, 9:40 am, Room 103A
Lithium ion batteries (LIBs) currently dominate the market and are expected to for another decade due to incremental improvements. However, with performance approaching intrinsic material limits, LIBs cannot meet the increasing demands of electric vehicles and stationary storage. In the next decade both solid state and lithium–sulfur (Li-S) batteries will begin displacing LIBs. Central to both technologies is Li2S, which serves as the active cathode material in Li-S batteries and is the key precursor and cost driver for leading solid-state electrolytes. In both applications Li2S has demonstrated excellent performance when used in nanoparticle (NP) form. However, Li2S is very costly and commercially available only as micropowders with impurities being a major concern, reflecting the energy-intensive carbothermal reduction processes currently used for synthesis. In this paper we describe a green chemistry-inspired approach for synthesizing alkali sulfide (M2S, M = Li and Na) NPs through the reaction of hydrogen sulfide (H2S) gas with alkali metal-organic (M-R) complexes dissolved in solution. This thermodynamically favorable reaction occurs spontaneously and proceeds rapidly to completion with near 100% atom efficiency at ambient temperature, forming phase-pure, anhydrous M2S nanopowders that are readily separated from solution. H2S, a major industrial waste, is completely abated and the valuable hydrogen stored therein may be fully recovered as H2. The overall stoichiometry of the two step process is: 2M (s) + H2S (g) => M2S (s) + H2 (g)
As such, this innovative synthetic approach is expected to be scalable, energy-efficient, and cost-effective. In this presentation we describe the process chemistry, focusing on the role of the complexing agent (R) and solvent to control the yield, size, and morphology of the resulting M2S NPs.