Sulfur nanoparticles encapsulated in reduced graphene oxide nanotubes for flexible lithium-sulfur batteries

Rapid development of flexible electronic devices is promoting the design of flexible energy-storage devices. Lithium-sulfur (Li-S) batteries are considered as promising candidates for high energy density energy-storage devices. Therefore, flexible Li-S batteries are desired. In this study, we fabricated composite films of freestanding reduced graphene oxide nanotubes wrapped sulfur nanoparticles (RGONTs@S) by pressing RGONTs@S composite foams, which were synthesized by combining cold quenching with freeze-drying and a subsequent reduction process. These RGONTs@S composite films can serve as self-supporting cathodes for Li-S batteries without additional binders and conductive agents. Their interconnected tubular structure allows easy electron transport throughout the network and helps to confine the polysulfides produced during the charge/discharge process. As a result, the RGONTs@S composite films exhibited a high initial specific capacity, remarkable cycling stability, and excellent rate capability. More importantly, the RGONTs@S composite films can serve as electrodes in flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled using these electrodes and they displayed stable electrochemical performance at different bending states.