Confining sulfur in intact freestanding scaffold of yolk-shell nanofibers with high sulfur content for lithium-sulfur batteries

Nanostructure design holds great potential in fabricating sulfur electrodes that host a high sulfur loading and still attain high electrochemical utilization for the developing of high-energy-density lithium-sulfur（Li-S） batteries. In this contribution, we introduce the yolk-shell structure into a freestanding carbon nanofibers film and construct a complete hollow yolk-shell Ti O2/carbon nanofibers@void@TiN@carbon（TiO2-CNFs@void@Ti N@C） composite. With inherent double conductive network and strong adsorption capability for polysulfides, the Ti O2-CNFs@void@Ti N@C composite can not only provide sufficient electrical contact for the insulating sulfur, but also effectively entrap polysulfides for prolonged cycle life. As a result, an excellent capacity retention ratio of 60.9% after 1000 cycles at 1 C as well as a high capacity of688.5 mA h g-1 at 5 C rate is accomplished with the cells employing Ti O2-CNFs@void@TiN @C as a cathode substrate for sulfur. Moreover, the TiO2-CNFs@void@Ti N@C composite, with a high S mass loading of9.5 mg cm-2, delivers a superb areal capacity of 8.2 mAh cm-2.