Rational Design of Co3s4-Con@N-Doped Carbon Hollow Spheres with Polar S-Co-N Bond as Bifunctional Host Materials for Lithium-Sulfur Batteries

Abstract

As one of the candidates for next-generation energy conversion systems, lithium-sulfur (Li-S) batteries have attracted extensive research interest due to their large capacity density and abundant raw materials. However, the huge volume expansion, the insulating nature of sulfur and polysulfide shutting issues, limit the further development of Li-S batteries. Herein, a MOF-derived CoN nanoparticles embed in N-doped carbon layer are successfully constructed on the surface of Co 3 S 4 hollow sphere to form the Co 3 S 4 -CoN@NC heterostructure with strong S-Co-N bonds, which act as bifunctional host materials for Li-S batteries and show strong adsorption and high-efficiency catalysis for lithium polysulfide (LiPSs). The hollow structure pre-stores a buffer space for the volume change of the electrode, which also limits the dissolution of polysulfides. In addition, the carbon layer can improve the overall structural strength and electrical conductivity of the material. Co 3 S 4 -CoN heterostructure with strong S-Co-N bonds can capture LiPSs and accelerate the conversion of LiPSs. Co 3 S 4 -CoN@NC exhibits a high initial specific capacity of 1542 mA h g −1 at 0.1 C and a stable capacity of 872.6 mA h g −1 at 0.5 C after 100 cycles with a high Coulombic efficiency of nearly 100%. This strategy provides inspiration for the design of electrode materials for Li-S batteries.

Keywords: Li-S batteries, Shuttle effect, hollow structure, Heterostructure, bifunctional materials