The Radical Pathway Based on a Lithium‐Metal‐Compatible High‐Dielectric Electrolyte for Lithium–Sulfur Batteries

• Published in: Angewandte Chemie International Edition Vol. 57; no. 51; pp. 16732 - 16736
• Main Authors: Zhang, Ge, Peng, Hong‐Jie, Zhao, Chen‐Zi, Chen, Xiang, Zhao, Li‐Da, Li, Peng, Huang, Jia‐Qi, Zhang, Qiang
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 17.12.2018
• Edition: International ed. in English
• Subjects: Batteries; Compatibility; Dielectric strength; Electrolytes; Electrolytic cells; Flux density; high-dielectric systems; Lithium; Lithium sulfur batteries; Polysulfides; radicals; reaction mechanisms; Sulfur; Tetramethylurea; reaction mechanisms; high-dielectric systems; radicals; electrolytes; lithium-sulfur batteries
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201810132

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.