Enhanced Electrochemical Kinetics with Highly Dispersed Conductive and Electrocatalytic Mediators for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising energy-storage devices because of their high theoretical energy densities. However, the practical application of Li–S batteries is still impeded by the poor cycling performance and rate capability at practical conditions. In order to improve the performance of practical Li–S batteries, a hierarchical Mo₂C nanocluster/carbon nanosheets hybrid based hollow spherical material (Mo₂C/CHS) is designed and prepared. The hollow spheres composed of stacked carbon nanosheets can facilitate the infiltration of electrolyte. The ultrasmall and highly conductive Mo₂C nanocrystals are confined in the carbon nanosheets and expose more active sites for anchoring and conversion of lithium polysulfides and increase the number of the nuclei for Li₂S₂/Li₂S precipitation. Benefitting from the synergistic effects, Mo₂C/CHS greatly promotes electrochemical kinetics in Li–S batteries with high sulfur loading (5 mg cm⁻²). Even under lean electrolyte conditions (E/S = 7 μL mg_sulfur⁻¹), the Li–S batteries with Mo₂C/CHS added exhibit a discharge capacity of 904 mAh g⁻¹ at the high current rate of 0.5 C, and with 894 mAh g⁻¹ maintained after 200 cycles. This work provides a fundamental understanding of the electrochemical processes and guides the rational design of host and additive materials for practical Li–S batteries.