ZrO(NO3)2 as a functional additive to suppress the diffusion of polysulfides in lithium - Sulfur batteries

Abstract

Lithium sulfur battery is deemed to one of the most hopefully useable and cost-effective options beyond traditional lithium ion batteries. Nevertheless, the intermediates shuttle effect and the instability of the lithium metal anode are still the significance of barriers to the actual application of lithium sulfur battery. In this work, zirconium oxynitrate (ZrO(NO3)2), which delivers good thermal stability and little hygroscopicity, is proposed as a dual functional electrolyte additive to ameliorate the electrochemical performance of lithium sulfur batteries. For one thing, the ZrO2+ cations possess a strong affinity to sulfur, which can catalyze the conversion of dissolved polysulfides to S8. For another, ZrO(NO3)2 is negatively charged in the ether electrolyte because of the coordination ability of ZrO2+. It displays a strong repulsion to polysulfides which would effectively trap the dissolved polysulfides and prevent the polysulfides from diffusing into the electrolyte phase. Additionally, NO3− anions can be reduced and form a stable passivation film on Li-metal anode, which is beneficial to decrease the reacting activity of Li-metal anode upon polysulfides and stabilizing the surface topography of the Li-metal anode. Ultimately, the ZrO(NO3)2 electrolyte additive observably enhances the discharge capacity and cycle stability of Lithium sulfur battery.