Supercritical CO2 mediated incorporation of sulfur into carbon matrix as cathode materials towards high-performance lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries are considered among the most promising candidates for the next-generation electrochemical power sources. The incorporation of sulfur and carbon matrices is the most appropriate strategy to contain sulfur and suppress the soluble polysulfide shuttle. However, in the conventional methods including mechanical mixing, heat treatment and wet-chemistry synthesis, it is very difficult to guarantee the precise sulfur content, uniform sulfur distribution, and strong interaction between sulfur and carbon. Hence, a novel synthetic strategy that utilizes supercritical CO₂ (SC-CO₂) to fabricate C@S composites for Li–S batteries has been successfully developed. Taking the advantages of high infiltrability, excellent diffusivity and superior solvability, SC-CO₂ not only serves as an intercalator that penetrates into the pores and interlayers of carbon matrices to expand/exfoliate the porous structure and tightly-stacked layered graphite structure, but also plays the role of a marvellous hydrophobic solvent to dissolve sulfur and transfer it into the inner pores and interlayers of carbon matrices. Taking AC@S as an example, it exhibits the highly reversible capacity of 817 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, and excellent cycling stability with a satisfactory capacity retention of 90.5%. We believe that this novel strategy will open up the prospects for synthesizing more efficient C/S composites to suppress the diffusion of polysulfides and enhance the structural stability and reaction kinetics of the sulfur cathode.