Hydroxylated N-doped carbon nanotube-sulfur composites as cathodes for high-performance lithium-sulfur batteries

Abstract

Despite the higher energy density than the conventional Li-ion cells at a lower cost, commercialization of LiS batteries is hindered by the insulating nature of sulfur and the dissolution of intermediate polysulfides (Li2SX, 4 < X ≤ 8) into the electrolyte. We demonstrate here hydroxylated N-doped carbon nanotubes (H-NCNT) as sulfur containers in lithium-sulfur batteries to reduce polysulfide shuttling through an interaction between polysulfides and nitrogen and hydroxyl groups in the H-NCNT. This sulfur-carbon composite electrode with 2.2 mg cm−2 sulfur displays excellent performance with high rate capability (initial capacity of 1341 mAh g−1 at C/5 rate and 849 mAh g−1 at 5C rate), rate stability until 500 cycles (a decay of 0.06% per cycle). Furthermore, a stable reversible capacity of as high as ∼1081 mAh g−1 is realized with a higher sulfur loading of 5.1 mg cm−2.