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

Wide operation temperature is the crucial objective for an energy storage system that could be applied under harsh environmental conditions. For lithium-sulfur batteries, the "shuttle effect" of polysulfide intermediates would 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 Li 2 S 8 to Li 2 S 4 , which would be another rate-determining step of sulfur conversion reaction, in addition to the solid-phase conversion process of Li 2 S 4 to Li 2 S 2 /Li 2 S at low temperatures. Porous bismuth vanadate (BiVO 4 ) spheres have been 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 the 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 BiVO 4 spheres as the host exhibits excellent rate capability and cycle performance under wide working temperatures with a reversible capacity of 970 mAh g -1 after 450 cycles at 70 °C, as well as the initial discharge capacity of 732 mAh g -1 at -40 °C. This article is protected by copyright. All rights reserved.