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

Abstract

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 S_1−xSe_x/C (x ≤ 0.1) composites have been prepared starting from Se and S powders at 260 °C. Raman spectra reveal the existence of S–Se bonds in S_1−xSe_x/C composites. As cathodes for lithium–sulfur batteries, S_1−xSe_x/C (x ≤ 0.1) composites exhibit high electrochemical performance in a carbonate-based electrolyte. S_0.94Se_0.06/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.