Identifying the active sites and multifunctional effects in nitrogen-doped carbon microtube interlayer for confining-trapping-catalyzing polysulfides

Lithium-sulfur batteries (LSBs) are recognized as promising energy storage devices for their high theoretical energy density. However, the unresolved “shuttle effect” limits the practical performance. The conventional strategies to inhibit lithium polysulfide (LiPS) shuttles including physical blocking and chemical anchoring are easy to hit the ceiling, which is mainly due to the sluggish sulfur redox kinetics. Herein, we report a self-standing nitrogen-doped carbonized cotton cloth (N-CCC) interlayer with macroscopic knitted structure and microscopic carbon microtubes for confining-trapping-catalyzing LiPS simultaneously. In situ/Operando characterization (including electrochemical impedance spectroscopy, shuttle current measurement and Raman spectroscopy) and theoretical calculation synergistically demonstrate that the multifunctional active sites of Pyrrolic N and Pyridinic N on N-CCC accelerate catalytic reaction kinetics and inhibit the “shuttle effect”. With the multifunctional N-CCC interlayer, a high capacity of 998 mAh g−1 at 2 C and high stability with a retention of 76% after 400 cycles are realized. Moreover, N-CCC based LSBs display competitive performance even at high current density (596 mAh g−1 @10 C) and high sulfur loading (795 mAh g−1 @4 mg cm−2 at 1 C). This research demonstrates a rational mechanism analysis for sulfur redox kinetics for practical high-energy/power density LSBs.