In situ carbon nanotube clusters grown from three- dimensional porous graphene networks as efficient sulfur hosts for high-rate ultra-stable Li-S batteries

Carbon nanotube （CNT） clusters grown in situ in three-dimensional （3D） porous graphene networks （3DG-CNTs）, with integrated structure and remarkable electronic conductivity, are desirable S host materials for Li-S batteries. 3DG-CNT exhibits a high surface area （1,645 m^2·g^-1）, superior electronic conductivity of 1,055 S·m^-1, and a 3D porous networked structure. Large clusters of CNTs anchored on the inner walls of 3D graphene networks act as capillaries, benefitting restriction of agglomeration by high contents of immersed S. Moreover, the capillary-like CNT clusters grown in situ in the pores efficiently form restricted spaces for Li polysulfides, significantly reducing the shuttling effect and promoting S utilization throughout the charge/discharge process. With an areal S mass loading of 81.6 wt.%, the 3DG-CNT/S electrode exhibits an initial specific capacity reaching 1,229 mA·h·g^-1 at 0.5 C and capacity decays of 0.044% and 0.059% per cycle at 0.5 and 1 C, respectively, over 500 cycles. The electrode material also reveals a remarkable rate performance and the large capacity of 812 mA·h·g^-1 at 3 C.