A high sulfur content composite with core–shell structure as cathode material for Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries have received significant attention in recent years because of their high theoretical specific capacity (1675 mA h g⁻¹) and energy density (2600 W h kg⁻¹). Many papers focus on cells that exhibit very high capacity per gram of sulfur, which contain sulfur contents well below 50% which greatly reduces their overall energy density per gram of cathode. Moreover, they do not address the issues of practical sulfur loading and large-scale technology for commercial applications. In general, the lower the sulfur content, the higher the sulfur capacity. In this paper, a high sulfur content (80% S) carbon–sulfur (P-AB@S) material with core–shell structure has been successfully synthesized by grafting of polymer electrolyte (polyethylene glycol, PEG) chains and depositing sulfur onto the surface of electronically conductive acetylene black (AB). The PEG chains are inserted into the sulfur layer to reinforce the material’s structural stability. More importantly, with a cathode containing 66% sulfur and approximately 3 mg cm⁻² sulfur loading on the electrode, P-AB@S as a cathode material for lithium sulfur batteries shows a specific capacity of 577 mA h g⁻¹ after 500 cycles at 100 mA g⁻¹ between 1.5 V and 2.8 V. Moreover, the preparation method of the P-AB@S composite is a facile, cost-effective and template-free method and easy to implement large-scale technology for commercial applications.