Practical Lithium–Sulfur Batteries Enabled by a Six-Membered Cyclic Urea Solvent

Highly solvating electrolytes hold great prospects for achieving the goal of practically high-energy-density lithium–sulfur batteries, yet they suffer from short cycle life due to their poor compatibility with Li-metal anode (LMA). Herein, a new six-membered cyclic urea, N, N′-dimethylpropyleneurea (DMPU), was rationally proposed as an electrolyte solvent to conquer this longstanding contradiction. The DMPU with high electron donicity preferentially coordinates with Li+ to dominate the inner-solvation shell, which not only initiates and stabilizes the S3•– radical to facilitate S redox kinetics and 3D Li2S deposition but also suppresses its contact reaction with LMA kinetically. More encouragingly, the DMPU molecule with a six-membered ring bears small ring strain, thus weakening their reactivity with LMA thermodynamically. Consequently, the DMPU-based electrolyte bestows an extremely high area capacity of 8.4 mAh cm–2 for a practical lithium–sulfur cell under a high S mass loading of 8.2 mg cm–2 and ultralow E/S ratio of 3.8 μL mgsulfur–1.