Free-standing integrated cathode derived from 3D graphene/carbon nanotube aerogels serving as binder-free sulfur host and interlayer for ultrahigh volumetric-energy-density lithium-sulfur batteries

The actual applications of lithium sulfur (Li-S) batteries are significantly obstructed by limited cyclability and low volumetric-energy-density due to the shuttling effect of polysulfides and low mass density of sulfur cathode. Herein, we report a free-standing, compact, conductive and integrated cathode (G/CNT-S//G/CNT), constructed by compressing graphene/carbon nanotubes (G/CNT) aerogels, simultaneously serving as bi-functionalities of binder- and metal-current-collector-free sulfur host (G/CNT-S) and interlayer (G/CNT), for high volumetricenergy-density Li-S batteries. The G/CNT aerogels display three-dimensional interconnected porous network, large surface area (363 m(2) g(-1)) and high electrical conductivity (67 S m(-1)), which can endow the cathode with ultrahigh volumetric mass density (1.64 g cm(-3)) and superior electron-ion transport network. Meanwhile, the compressed ultralight G/CNT film can act as flexible interlayer for synergistically suppressing the polysulfide shuttling via both chemical interaction and physical restriction. Consequently, the compact cathodes, achieve high capacity of 1286 mAh g(-1) at 0.2 C and long-term cyclability with an extremely low decay rate of 0.06% over 500 cycles at 2 C. Most importantly, our compact cathodes represent unprecedented volumetric capacity of 1841 Ah L-1 and volumetric-energy-density of 2482 Wh L-1, both of which are the highest values of Li-S batteries reported to date. Therefore, this proposed strategy will open a new avenue for developing high volumetric-energy-density Li-S batteries.