The Radical Pathway Based on a Lithium-Metal-Compatible High-Dielectric Electrolyte for Lithium-Sulfur Batteries.

High-dielectric solvents were explored for enhancing the sulfur utilization in lithium-sulfur (Li-S) batteries, but their applications have been impeded by low stability at the lithium metal anode. Now a radical-directed, lithium-compatible, and strongly polysulfide-solvating high-dielectric electrolyte based on tetramethylurea is presented. Over 200 hours of cycling was realized in Li|Li symmetric cells, showing good compatibility of the tetramethylurea-based electrolyte with lithium metal. The high solubility of short-chain polysulfides, as well as the presence of active S3 .- radicals, enabled pouch cells to deliver a discharge capacity of 1524 mAh g-1 and an energy density of 324 Wh kg-1 . This finding suggests an alternative recipe to ether-based electrolytes for Li-S batteries.