Synergistically Assembled Li₂S/FWNTs@Reduced Graphene Oxide Nanobundle Forest for Free-Standing High-Performance Li₂S Cathodes

Lithium sulfide (Li₂S) has attracted increasing attention as a promising cathode because of its compatibility with more practical lithium-free anode materials and its high specific capacity. However, it is still a challenge to develop Li₂S cathodes with low electrochemical overpotential, high capacity and reversibility, and good rate performance. This work designs and fabricates a practical Li₂S cathode composed of Li₂S/few-walled carbon nanotubes@reduced graphene oxide nanobundle forest (Li₂S/FWNTs@rGO NBF). Hierarchical nanostructures are obtained by annealing the Li₂SO₄/FWNTs@GO NBF, which is prepared by a facile and scalable solution-based self-assembly method. Systematic characterizations reveal that in this unique NBF nanostructure, FWNTs act as axial shafts to direct the structure, Li₂S serves as the internal active material, and GO sheets provide an external coating to minimize the direct contact of Li₂S with the electrolyte. When used as a cathode, the Li₂S/FWNTs@rGO NBF achieve a high capacity of 868 mAh g⁻¹ _Li2S at 0.2C after 300 cycles and an outstanding rate performance of 433 mAh g⁻¹ _Li2S even at 10C, suggesting that this Li₂S cathode is a promising candidate for ultrafast charge/discharge applications. The design and synthetic strategies outlined here can be readily applied to the processing of other novel functional materials to obtain a much wider range of applications.