Hydrothermal synthesis of boron-doped unzipped carbon nanotubes/sulfur composite for high-performance lithium-sulfur batteries

A boron-doped unzipped carbon nanotubes/sulfur (BUCNTs/S-1) composite was first prepared via a one-pot facile hydrothermal process by using oxidized unzipped carbon nanotubes (O-UCNTs), boron acid and element sulfur as the carbon precursor, B and S sources, respectively. The morphology, structure and composition of the BUCNTs/S-1 composite were characterized and the effect of B doping and sulfur loading were also investigated in details. The results demonstrated that the participation of B atom and sulfur loading achieved by hydrothermal method endowed the BUCNTs host with enhanced conductivity, promoted sulfur dispersibility and strengthened adsorbability for the sulfur species. The electrochemical performances of the BUCNTs/S-1 used as lithium-sulfur cathodes were then studied. Benefitting from all the merits, the BUCNTs/S-1 cathode delivered a high initial capacity of ∼1251 mAh/g at 0.2C, retaining as high as ∼750 mAh/g after 400 cycles, displaying significantly enhanced cycling stability. Hence, this work provides a facile method to fabricate a promising sulfur cathode candidate for high performance lithium-sulfur batteries.