Fluorinated bamboo-structure carbon nanotubes: as attractive substrates for the cathodes of lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have gained considerable attention for high theoretical specific capacity and energy density. However, their development is hampered by the poor electrical conductivity of sulfur and the shuttle of polysulfides. Herein, the acidified bamboo-structure carbon nanotubes (BCNTs) were mixed with polyvinylidene difluoride and pyrolyzed at high-temperature to obtain the fluorinated bamboo-structure carbon nanotubes (FBCNTs), which were compounded with sulfur as the cathode. The prepared S@FBCNTs with sulfur loading reaching 74.2 wt.% shows a high initial specific capacity of 1407.5 mAh center dot g-1 at the discharge rate of 0.1 C. When the discharge rate was increased to 5 C, the capacity could be maintained at 622.3 mAh center dot g-1. The electrical conductivity of carbon nanotubes is effectively improved by semi-ionic C-F bonds formed by the doped F atoms and carbon atoms. Simultaneously, the surface of the F-containing carbon tubes exhibits strong polarity and strong chemisorption effect on polysulfides, which inhibits the shuttle effect of Li-S batteries.