Preparation of a lithium–sulfur battery diaphragm catalyst and its battery performance

Abstract

Lithium–sulfur batteries (LSBs) with metal lithium as the anode and elemental sulfur as the cathode active materials have attracted extensive attention due to their high theoretical specific capacity (1675 mA h g⁻¹), high theoretical energy density (2600 W h kg⁻¹), low cost, and environmental friendliness. However, the discharge intermediate lithium polysulfide undergoes a shuttle side reaction between the two electrodes, resulting in low utilization of the active substances. This limits the capacity and cycle life of LSBs and further delays their commercial development. However, the number of active sites and electron transport capacity of such catalysts still do not meet the practical development needs of lithium–sulfur batteries. In view of these issues, this paper focuses on a zinc–cobalt compound catalyst, modifying it through heteroatom doping, bimetallic synergistic effect and heterogeneous structure design to enhance the performance of LSBs as a separator modification material. A carbon shell-supported boron-doped ZnS/CoS₂ heterojunction catalytic material (B–ZnS/CoS₂@CS) was prepared, and its performance in lithium–sulfur batteries was evaluated. A carbon substrate (CS) was prepared by pyrolysis of sodium citrate, and the boron-doped ZnS/CoS₂ heterojunction catalyst was formed on the CS using a one-step solvothermal method. The unique heterogeneous interface provides numerous active sites for the adsorption and catalysis of polysulfides. The uniformly doped, electron-deficient boron further enhances the Lewis acidity of the ZnS/CoS₂ heterojunction, while also regulating electron transport. The B–ZnS/CoS₂@CS catalyst effectively inhibits the diffusion of LiPS anions by utilizing additional lone-pair electrons. The lithium–sulfur battery using the catalyst-modified separator achieves a high specific capacity of 1241 mA h g⁻¹ at a current density of 0.2C and retains a specific capacity of 384.2 mA h g⁻¹ at 6.0C. In summary, B–ZnS/CoS₂@CS heterojunction catalysts were prepared through boron doping modification. They can promote the conversion of polysulfides and effectively inhibit the shuttle effect. The findings provide valuable insights for the future modification and preparation of lithium–sulfur battery catalysts.