Super-aligned carbon nanotube/graphene hybrid materials as a framework for sulfur cathodes in high performance lithium sulfur batteries

Abstract

We report the use of super-aligned carbon nanotube/graphene (CNT/G) hybrid materials as a 3D conducting framework for sulfur accommodation. The CNT network acts as a skeleton to form a self-sustained cathode that is binder-free, highly conductive, and flexible. Graphene with a 2D sheet structure extends in an additional dimension to provide improved restriction for sulfur/polysulfides. Moreover, the CNT/G hybrid framework enables better dispersion of sulfur and allows each sulfur particle to closely attach to the conductive components, which greatly enhance the electronic conductivity and thereby approach the full potential of the active materials. With an optimized CNT/G ratio in the framework, the S–CNT/G nanocomposite exerts improved mechanical performance and favorable electrochemical characteristics compared to the S–CNT composite. Based on its superior structure, the S–CNT/G nanocomposite achieves a high discharge capacity of 1048 mA h g⁻¹ at 1 C with a capacity fade as low as 0.041% per cycle over 1000 charge–discharge cycles. Excellent high-rate and long-term cycling performances are also revealed. These results demonstrate the great potential of the S–CNT/G nanocomposite as a flexible and binder-free cathode for Li–S batteries.