S@C composites constructed by a graded pore-making strategy for Mg–S batteries with outstanding rate performance

Abstract

Rechargeable magnesium batteries (RMBs) are low-cost energy storage devices, but they lack suitable cathode materials. Traditional sulfur (S₈) cathodes have attracted much attention because of their high energy density; however, their cycling stability, conductivity, and reversibility are inferior. In this work, porous carbon materials with abundant pores were obtained by graded pore-making and S@C composite materials were obtained as cathodes for magnesium–sulfur batteries after loading porous carbon materials with sulfur. The interconnected pores provide the electrode material with a wealth of electrons and ion transport channels. The hollow structure of the carbon material facilitates the electrode–electrolyte contact area ensuring ion supply at high currents. Magnesium electricity assembled using S@C for the cathode had a high initial discharge specific capacity of 728 mA h g⁻¹ at 50 mA g⁻¹. When the magnification cycle reached 2000 mA g⁻¹, it still had a high discharge-specific capacity of 242 mA h g⁻¹, and the coulombic efficiency reached ∼100%, indicating excellent magnification performance. At a current density of 200 mA g⁻¹, the maximum discharge-specific capacity was 420 mA h g⁻¹. After 100 cycles, a discharge-specific capacity of ∼100 mA h g⁻¹ remained with good cycling stability. This work provides a general strategy for the preparation of porous carbon composites and new insights for high-rate energy storage systems.