Cathode materials based on carbon nanotubes for high-energy-density lithium-sulfur batteries

The rational integration of conductive nanocarbon scaffolds and insulative sulfur is an efficient method to build composite cathodes for high-energy-density lithium-sulfur batteries. The full demonstration of the high-energy-density electrodes is a key issue towards full utilization of sulfur in a lithium-sulfur cell. Herein, carbon nanotubes (CNTs) that possess robust mechanical properties, excellent electrical conductivities, and hierarchical porous structures were employed to fabricate carbon/sulfur composite cathode. A family of electrodes with areal sulfur loading densities ranging from 0.32 to 4.77 mg cm^-2 were fabricated to reveal the relationship between sulfur loading density and their electrochemical behavior. At a low sulfur loading amount of 0.32 mg cm^-2, a high sulfur utilization of 77% can be achieved for the initial discharge capacity of 1288 mAh g_S ^-1, while the specific capacity based on the whole electrode was quite low as 84 mAh g_{C/S+binder+Al}^-1 at 0.2 C. Moderate increase in the areal sulfur loading to 2.02 mg cm^-2 greatly improved the initial discharge capacity based on the whole electrode (280 mAh g _{C/S+binder+Al}^-1) without the sacrifice of sulfur utilization. When sulfur loading amount further increased to 3.77 mg cm ^-2, a high initial areal discharge capacity of 3.21 mAh cm ^-2 (864 mAh g_S^-1) was achieved on the composite cathode.