Wheat straw carbon matrix wrapped sulfur composites as a superior cathode for Li–S batteries

Abstract

A novel activated carbon material is prepared by pyrolysis of natural wheat straw waste with KOH activation. This carbon contains abundant micropores, possessing a large BET surface area of 1066 m² g⁻¹ and total pore volume of 0.62 cm³ g⁻¹ with an average pore size of 2.33 nm, which can enhance the adsorption of polysulfides and sulfur by capillary force. The treated carbon is used to synthesize a wheat straw carbon (WSC)/S composite as the cathode of Li–S batteries for the first time. The WSC/S composite with 74 wt% sulfur content exhibits a high initial discharge capacity of 1213 mA h g⁻¹ at 0.1C (1C = 1675 mA g⁻¹) with coulombic efficiency of 95% and a superior rate capability. Even when cycling at 1C, the first and the 200^th specific discharge capacity of 582 mA h g⁻¹ and 445 mA h g⁻¹ are retained, respectively, along with a low fading rate of 0.11% per cycle, which suggests that the WSC/S composite could be a type of promising material for cathodes of Li–S batteries.