Graphene-Based Hierarchically Micro/Mesoporous Nanocomposites as Sulfur Immobilizers for High-Performance Lithium–Sulfur Batteries

Herein, a hierarchically micro/mesoporous nano composite of graphene and carbon nanospheres (HGC) is used as an immobilizer for a lithium-sulfur (Li-S) battery with enhanced performance. HGC derived from graphene oxides and polyvinylidene fluoride polymers, combined with the advantages of graphene and porous carbon nanospheres, exhibits a hierarchically micro/mesoporous structure with an ultralarge specific surface area of up to 3182 m(2) g(-1) and a large pore volume of 1.91 cm(3) g(-1). Graphene as a conducting network can enhance electronic conductivity, while porous nanospheres like a reservoir can effectively store and immobilize sulfur particles. HGC/sulfur electrode material obtained via a melting infusion process exhibits high reversible specific capacity of 1250 mA h g(-1) with a high sulfur content of 74.5 wt %, and it still has a capacity of 916 mA h g(-2) after 100 cycles, which is better than that of pristine porous graphene and carbon nanospheres. Furthermore, the relative capacity decay of the HGC/sulfur electrode is only 0.005 and 0.004% per cycle at 2 C and 4 C, respectively, after 450 charge/discharge cycles, exhibiting remarkable performance in terms of long-term electrochemical stability.