Encapsulation of Sulfur into N-Doped Porous Carbon Cages by a Facile, Template-Free Method for Stable Lithium-Sulfur Cathode.

Lithium-sulfur (Li-S) batteries with a high energy density and long lifespan are considered as promising candidates for next-generation electrochemical energy-storage devices. However, the sluggish redox kinetics of electrochemistry and high solubility of polysulfide during cycling render insufficient sulfur utilization and poor cycling stability. Herein, a facile, template-free procedure based on controlled pyrolysis of polydopamine vesicles is described to prepare N-doped porous carbon cages (NHSC) as a new sulfur host, which significantly improves both the sulfur utilization and cycling stability. As NHSC shows a high pore volume, continuous electron and ion transport paths, and good catalytic activity, encapsulation of S nanoparticles into NHSC endows the resulting S@NHSC electrode with a good energy storage capacity and exceptionally high electrochemical stability. Consequently, a Li-S cell with the S@NHSC as the cathode achieves a high initial capacity of 1280.7 mAh g-1 , and cycling stability over 500 cycles with the capacity decay as low as 0.0373% per cycle.