Hierarchical Nanostructured Carbon/Sulfur Hybrid Cathode for High-Performance Lithium-Sulfur Battery

Among various energy storage/conversion systems, lithium-sulfur batteries are considered as one of the most promising candidate due to not only very high theoretical energy density of 2600 Wh kg^-1 (based on lithium-sulfur redox couple) and wide operating temperature range benefiting from its unique multiple-electron-transfer chemistry, but also abundant reserves and environmental friendliness of sulfur. However, several intrinsic obstacles should be overcome for its applicably extension, including the ultra-low electrical conductivity of sulfur and its lithiated products, huge volumetric changes during charge and discharge, and the shuttling mechanism of soluble intermediate polysulfides.

Here, a hierarchical nanostructured carbon/sulfur hybrid in which the porous carbon was in situ integrated into graphene/single-walled carbon nanotube (SWCNT) hybrid matrix with small cyclo-S₈ molecule clusters was fabricated as advanced cathode material for lithium-sulfur battery application. The sp² graphene/SWCNT hybrid interlinked framework was served as robust conductive scaffold with good electrical conductivity and structure stability, while the micro-/mesoporous carbon accommodated sulfur and lithium polysulfides, provided accessibility for liquid electrolyte to active material, and suppress the shuttle behavior due to the spacial confinement. Therefore, such hierarchical all-carbon nanostructure hybridized with small cyclo-S₈ molecule clusters obtained an excellent electrochemical performance including an ultrahigh specific capacity of 1121 mAh g^-1 at 0.5 C, a favorable high-rate capability of 809 mAh g^-1 at 10 C, a very low capacity decay of 0.12 % per cycle, and an impressive cycling stability of 877 mAh g^-1 after 150 cycles at 1 C. As sulfur loading increasing from 50 wt % to 77 wt %, high capacities of 970, 914, and 613 mAh g^-1 were still available at current densities of 0.5, 1, and 5 C respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC-S//Li cell was expected to be 400 Wh kg^-1 at a power density of 10000 W kg^-1, matching the level of engine driven systems.

Reference:

[1] HJ Peng, et al. Adv. Funct. Mater., 2014, DOI: 10.1002/adfm.201303296