Sub-nanometer cobalt clusters embedded carbon networks to promote the kinetics of polysulfide conversion

Abstract

The sluggish oxidation-reduction kinetics of sulfur and the shuttle effect of polysulfides are the bottlenecks restricting the practical application of lithium-sulfur batteries. In this study, subnanometer cobalt clusters were embedded into the cross-linked network of carbon sheets framework as high-efficiency sulfur host materials to promote the kinetics of polysulfides conversion for lithium-sulfur batteries. In such composite structure, the carbon network provides a rapid electron transfer pathway for interfacial electrochemical reaction. Co and N atoms can chemisorb polysulfides by forming Co-S and Li-N bonds with polysulfides, and catalyze the conversion of polysulfides. Such structure exhibits excellent rate performance and cycle stability during the cycle of lithium-sulfur battery. The capacity decay rate per cycle is only 0.061% for 500 cycles at 1 C, and the capacity retention rate is 69.4%. The composite structure developed in this work is a promising and high-efficiency sulfur host for lithium-sulfur batteries.