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. Li−S batteries: A lithium‐compatible and strongly polysulfide‐solvating high‐dielectric electrolyte based on tetramethylurea was proposed to direct a solvation‐mediated radical reaction pathway. It enables Li−S pouch cells to deliver an energy density of 324 Wh kg−1. Key: red=electrochemical, black=chemical, dashed=diffusion/precipitation. [ABSTRACT FROM AUTHOR]