Revealing a volcano correlation of sulfur reduction catalytic activity and elements doping in cobalt-based sulfides for Li-S batteries

The effective utilization of Li-S batteries still necessitates the incorporation of an efficient catalytic medium to address the challenges posed by shuttle effects and sluggish reaction kinetics. Furthermore, the structure-activity relationship of catalysts for the sulfur reduction reaction remains inadequately understood. In this study, we utilize Co ₉S ₈ as a template to investigate the correlation between the doping of co-periodic elements (Fe, Ni, Cu and Zn) and their catalytic effects on the sulfur reduction reaction. There is a “volcano peak” correlation between the catalytic performance and the type of doped elements from Fe to Zn, and research indicates that the Ni-doped Co ₉S ₈ (NCS) demonstrates superior performance compared to other samples. The NCS not only maintains the inherent advantages of Co ₉S ₈ but also effectively lowers the apparent activation energy necessary for Li-S batteries. Consequently, this enhancement facilitates a more rapid and complete conversion of soluble lithium polysulfides, thereby endowing Li-S batteries with an enhanced reaction kinetics. When the sulfur areal loading is elevated to 5.2 mg cm ⁻², the maximum areal capacity of the cell can attain 5.2 mAh cm ⁻² at 0.05 C. This work further substantiates the efficacy of the element doping strategy in enhancing the catalytic performance of reduction reaction catalysts, and it also offers significant insights or considerations for the development of practical catalysts, thereby facilitating the practical application of Li-S batteries.