Free-standing graphene-based porous carbon films with three-dimensional hierarchical architecture for advanced flexible Li-sulfur batteries

Sulfur shows a large lithium-storage capacity and this make it an attractive cathode candidate for next-generation flexible lithium-ion batteries. However, the insulating nature of sulfur and the dissolution of intermediate polysulfides limit the rate performances and cycle life of Li-sulfur batteries. Here, we report a class of free-standing cathode films consisting of hierarchically porous carbon-encapsulated sulfur have high rate capability (a reversible capacity of 1017 mA h g^-1, 865 mA h g^-1, and 726 mA h g^-1 at 0.2 C, 0.5 C and 1 C, respectively) as well as excellent cycle stability (approximate 10.5% capacity loss after 300 cycles). In addition, the free-standing cathode films have good mechanical flexibility, and thus show remarkable lithium-storage performances at the bent state. The results indicate that such free-standing cathode films with 3D hierarchical structure will provide new opportunities for Li-sulfur batteries for applications in flexible electronic devices.