Nitrogen-doped holey carbon nanotubes: Dual polysulfides trapping effect towards enhanced lithium-sulfur battery performance

Abstract Advanced sulfur hosts decorated with unique structure, optimized composition and excellent conductivity play a vital role in improving lithium-sulfur battery performance. Herein, we first prepare oxidized holey carbon nanotubes (O-H-CNTs) through a controlled air etching strategy, then exploit them as the carbon precursor to produce nitrogen-doped holey carbon nanotubes (N-H-CNTs). The influence of air etching degree on the morphology, structure, composition, conductivity and post-doping effect of O-H-CNTs is discussed in detail. The optimized O-H-CNTs-2 (2 refers to etching time) display unique holey structure and obtain a certain amount of structure defects while retaining good conductivity. After N doping, the resultant N-H-CNTs-2 host exhibits improved conductivity and promoted sulfur dispersibility. More importantly, the unique holey structure and effective N doping endow them with strengthened dual trapping capability for polysulfides. Therefore, the N-H-CNTs-2/S cathode shows much enhanced cycling lifespan and rate performance. It delivers a high discharge capacity of over 750 mAh/g even after 500 cycles, and high rate capacity of ∼560 mAh/g at 4 C. Clearly, our work provides a good guidance on the design and exploitation of excellent sulfur host by rationally regulating the structure, composition and conductivity.