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 Li(2)SO4/ 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.