Supercritical CO2 assisted fabrication of activated carbon-sulfur composite for improved lithium-sulfur batteries

•A general approach to make improved cathode materials for Li-S battery.•Liquid- and gas-like supercritical CO2 facilitates sulfur loading in porous carbon.•Better dispersion and electrical contact of sulfur in activated carbon.•Suppress shuttle effect and improve the electrical conductivity of sulfur.

In order to alleviate the shuttle effect and improve the electrical conductivity of sulfur in Li-S batteries, supercritical CO2 (scCO2) assisted deposition was demonstrated to impregnate sulfur into activated carbon for fabricating high performance cathode materials. Activated carbon and sulfur were agitated in CS2-modified scCO2 at 100 °C and 150 bar for 3 h. The appreciable densities and solvent power, combined with low viscosity, low surface tension and high diffusivity of scCO2, facilitated highly dispersed impregnation of high loading percentage of sulfur into porous structure of activated carbon whilst enabling excellent electrical contact. Lab Li-S battery test showed that after 150 cycles under current density of 0.5 C, the resultant carbon-sulfur composite exhibited a capacity retention of ∼60%, higher than that of ∼45% for the counterpart prepared by melting infiltration.