Accelerating the Rate-Determining Steps of Sulfur Conversion Reaction for Lithium-Sulfur Batteries Working at an...

Wide operation temperature is the crucial objective for an energy storage system that can be applied under harsh environmental conditions. For lithium-sulfur batteries, the "shuttle effect" of polysulfide intermediates will aggravate with the temperature increasing, while the reaction kinetics decreases sharply as the temperature decreasing. In particular, sulfur reaction mechanism at low temperatures seems to be quite different from that at room temperature. Here, through in situ Raman and electrochemical impedance spectroscopy studies, the newly emerged platform at cryogenic temperature corresponds to the reduction process of Li₂S₈ to Li₂S₄, which will be another rate-determining step of sulfur conversion reaction, in addition to the solid-phase conversion process of Li₂S₄ to Li₂S₂/Li₂S at low temperatures. Porous bismuth vanadate (BiVO₄) spheres are designed as sulfur host material, which achieve the rapid snap-transfer-catalytic process by shortening lithium-ion transport pathway and accelerating the targeted rate-determining steps. Such promoting effect greatly inhibits severe "shuttle effect" at high temperatures and simultaneously improves sulfur conversion efficiency in the cryogenic environment. The cell with the porous BiVO₄ spheres as the host exhibits excellent rate capability and cycle performance under wide working temperatures.