Novel nitrogen-doped bamboo-structure carbon nanotubes as superior sulfur host for high-performance lithium-sulfur batteries

Abstract

In this work, nitrogen-doped bamboo-structure carbon nanotubes (BCNTs) with large diameters (ranging from 50 nm to 300 nm), high specific surface area (437.41 m2·g−1) and thin tube wall (less than 8 carbon layers) were prepared as sulfur host for lithium-sulfur (Li-S) batteries. Sulfur nanoparticles (NPs) with diameters of 20–30 nm were in-situ synthesized on the surface of BCNTs by a facile ultrasonic treatment, which can enhance the binding ability between sulfur and carbon, and then improve the utilization of sulfur. It is found that the in-situ synthesized S@BCNTs composite cathode with a high sulfur content of 62.2 wt% exhibits an initial specific capacity of 1008.4 mAh·g−1 at a current density of 0.1 C, and can still maintain a capacity of 383.9 mAh·g−1 after 500 cycles. Careful composition and microstructure analyses reveal that these excellent electrochemical performance can be ascribed to the synergistic effect of conductive nitrogen doping (especially pyridinic-N and pyrrolic-N) and homogeneous sulfur coating on the surface of BCNTs, which contributes to accelerating electron transport, adsorbing polysulfides and alleviating the shuttle effect. As a result, the as-prepared nitrogen-doped BCNTs can be pretty promising cathode materials for Li-S batteries. This work can open up a new possibility for the design of stable Li-S cathodes for high-performance batteries.