Quantitative defect regulation of heterostructures for sulfur catalysis toward fast and long lifespan lithium-sulfur batteries

The advancement of lithium-sulfur (Li-S) batteries is severely retarded by lithium polysulfides (LiPSs) shuttling behavior and sluggish redox kinetics. Herein, the heterogeneous composite with defective Bi₂Se_3−x nanosheets and porous nitrogen-doped carbon (Bi₂Se_3−x/NC) is prepared by selenizing bismuth metal-organic frameworks as a multifunctional sulfur host. The highly efficient immobilization-conversion on LiPSs is realized by the synergistic effect of structure construction strategy and defect engineering. It is found that Bi₂Se_3−x with the suitable amount of selenium vacancies achieves the best electrochemical performance due to the advantages of its structure and composition. These results confirm the intrinsic correlation between defects and catalysis, which are revealed by computational and experimental studies. Due to these superiorities, the developed sulfur electrodes exhibited admirable stability and a fairly lower capacity decay rate of approximately 0.0278% per cycle over 1,000 cycles at a 3 C rate. Even at the high sulfur loading of 6.2 mg·cm⁻², the cathode still demonstrates a high discharge capacity of 455 mAh·g⁻¹ at 1 C. This work may enlighten the development of mechanism investigation and design principles regarding sulfur catalysis toward high-performance Li-S batteries.