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

Highlights: • 3D flexible and compressed graphene/carbon nanotube framework, simultaneously serving as free-standing and integrated sulfur host and interlayer for lithium sulfur batteries. • The integrated electrode achieves high capacity 1286 mAh g⁻¹, and exceptionally long-term cyclability with ultrahigh volumetric sulfur loading of 1.64 g cm⁻³. • The compact electrode shows record volumetric capacity of 1841 Ah L⁻¹, and volumetric energy density of 2482 Wh L⁻¹. -- Abstract: The actual applications of lithium sulfur (LiS) 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 volumetric-energy-density LiS batteries. The G/CNT aerogels display three-dimensional interconnected porous network, large surface area (363 m² 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 LiS batteries reported to date. Therefore, this proposed strategy will open a new avenue for developing high volumetric-energy-density LiS batteries.