Amorphous S-rich S1-xSex/C (x <= 0.1) composites promise better lithium-sulfur batteries in a carbonate-based electrolyte

Polysulfide dissolution and the insulating nature of sulfur cause significant capacity fading and low efficiency in rechargeable lithium-sulfur batteries. Here, we show that these defects can be effectively diminished by immobilizing sulfur in porous carbon via the interaction of a small amount of selenium. Amorphous S-rich S1-xSex/C (x <= 0.1) composites have been prepared starting from Se and S powders at 260 degrees C. Raman spectra reveal the existence of S-Se bonds in S1-xSex/C composites. As cathodes for lithium-sulfur batteries, S1-xSex/C (x <= 0.1) composites exhibit high electrochemical performance in a carbonate-based electrolyte. S0.94Se0.06/C composites deliver the best performance with a capacity of 910 mA h g(-1) at 1 A g(-1) over 500 cycles, 1105 mA h g(-1) at 0.2 A g(-1) after 100 cycles and a good rate capability of 617 mA h g(-1) at 20 A g(-1).