Sustainable S cathodes with synergic electrocatalysis for room-temperature Na–S batteries

Abstract

A novel sulfiphilic host is reported with single Co atoms (Co₁) and ZnS quantum dots (ZnS-QDs) (∼10 nm) grown in N-doped carbon microparticles. The introduction of Co cations into the precursor is crucial, because it leads to the dispersion of single-atom Co on the carbon matrix, decreasing the size and improving the dispersion of the resultant ZnS-QDs as well. Benefitting from the resilient and stable carbon framework, the single-atom Co and small ZnS-QDs synergically electro-catalyze the S redox process, which can greatly enhance sodium polysulfide conversion and reduction of non-conductive Na₂S. The refined S cathode achieves remarkable cycling capability (640 mA h g⁻¹ after 500 cycles at 0.1 A g⁻¹), enhanced capacity retention, and outstanding energy density (541 W h kg⁻¹), giving it great promise for scientific research and practical applications.