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.

As promising candidates for energy-storage devices, supercapacitors (SCs) have attracted considerable attention because of their unique features, such as their high power density, outstanding rate capability, excellent cycling performance, and safety. The recent boom in portable electronic devices requires high- performance SCs that are flexible, simplified, thin, and integrated. Tremendous efforts have been directed towards the design and integration of planar micro- SCs (MSCs) based on different active electrode materials by various methods. This review highlights the recent developments in the device design of flexible planar MSCs and their integration with other electronic devices. The current challenges and future prospects for the development of flexible MSCs are also discussed.