Composite of sulfur impregnated in porous hollow carbon spheres as the cathode of Li-S batteries with high performance

Abstract

Carbon-sulfur composites as the cathode of rechargeable Li-S batteries have shown outstanding electrochemical performance for high power devices. Here, we report the promising electrochemical charge-discharge properties of a carbon-sulfur composite, in which sulfur is impregnated in porous hollow carbon spheres (PHCSs) via a melt-diffusion method. Instrumental analysis shows that the PHCSs, which were prepared by a facile template strategy, are characterized by high specific surface area (1520 m²·g⁻¹), large pore volume (2.61 cm³·g⁻¹), broad pore size distribution from micropores to mesopores, and high electronic conductivity (2.22 S·cm⁻¹). The carbon-sulfur composite with a sulfur content of 50.2 wt.% displays an initial discharge capacity of 1450 mA·h·g⁻¹ (which is 86.6% of the theoretical specific capacity) and a reversible discharge capacity of 1357 mA·h·g⁻¹ after 50 cycles at 0.05 C charge-discharge rate. At a higher rate of 0.5C, the capacity stabilized at around 800 mA·h·g⁻¹ after 30 cycles. The results illustrate that the porous carbon-sulfur composites with hierarchically porous structure have potential application as the cathode of Li-S batteries because of their effective improvement of the electronic conductivity, the repression of the volume expansion, and the reduction of the shuttling loss.