Thermal Plasma Synthesis of Li2S Nanoparticles for Application in Lithium-Sulfur Batteries.

Inductively-coupled thermal plasma processes were used to produce nanosized Li₂S. Prior to the syntheses, the feasibility of forming Li₂S was first evaluated using FactSage by considering the phase diagrams of sulfur and different lithium precursors in reducing atmospheres; Li₂O, LiOH·H₂O, Li₂CO₃ and Li₂SO₄·H₂O all showed promises in producing Li₂S nanoparticles, as confirmed by experiments. Argon and hydrogen mixtures were used as plasma gases, and a carbothermal reduction was implemented for Li₂SO₄·H₂O. In addition, carbon-coated Li₂S nanoparticles were synthesized with downstream injection of methane. Carbon was shown to stabilize Li₂S upon contact with ambient air. The Li₂S nanoparticles were electrochemically tested in half-cells using electrolytes containing LiNO₃ or Li₂S₆ as additives. It was found that adding LiNO₃ to the electrolyte was detrimental to the electrochemical performance of Li₂S, whereas the combination of Li₂S₆ and LiNO₃ as additives doubled the charge and discharge capacities of the half-cell over 10 cycles. [ABSTRACT FROM AUTHOR]