High capacity cathode materials for Li–S batteries

To enhance the stability of sulfur cathode for a high energy lithium–sulfur battery, sulfur–activated carbon (S–AC) composite was prepared by encapsulating sulfur into micropores of activated carbon using a solution-based processing technique. In the analysis using the prepared specimen of S–AC composite by the focused ion beam (FIB) technique, the elemental sulfur exists in a highly dispersed state inside the micropores of activated carbon, which has a large surface area and a narrow pore distribution. The S–AC composite was characterized through X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method, selected area electron diffraction (SAED), energy dispersive X-ray spectrometry (EDX), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), and field emission scanning electron microscopy (FESEM). A lithium–sulfur cell using the S–AC composite has a high first discharge capacity over 800 mA h g⁻¹ S even at a high current density such as 2C (3200 mA g⁻¹ S) and has good cycleability around 500 mA h g⁻¹ S discharge capacity at the 50^th cycle at the same current density.