Brominated flame retardants coated separators for high-safety lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have become highly promising next-generation secondary lithium batter-ies owing to their high theoretical energy density and abundance of sulfur. Nevertheless, the large-scale application of LSBs is still restricted by the shuttle effect of lithium polysulfide (LiPSs) and the potential fire hazard caused by flammable electrolytes. Herein, three electrolyte-insoluble brominated flame retar-dants (BFRs) are selected and coated on both sides of commercial polypropylene separators by a facile slurry coating method. The effects of the three BFRs on the safety and electrochemical properties of LSBs are characterized and compared. The coating modification separators greatly improves the flame retardancy of LSBs through radical elimination mechanism. The self-extinguishing time of the electrolyte is reduced from 0.66 s/mg to 0.20 s/mg. Moreover, it is demonstrated that the oxygen (O)-containing BFRs exert a significant adsorption capacity and are more advantageous than O-free BFRs in LSBs. In addition, octabromoether (BDDP) coated separator is more effective in trapping LiPSs than decabromodiphenyl ether (DBDPO) due to higher O content, which can mitigate the shuttle effect and enhance the cycle and rate performance of LSBs. This simple coating strategy for separators with BFRs offers a strongly com-petitive option for the large-scale production of high-safety LSBs.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

Coating commercial polypropylene separators with three brominated flame retardants greatly improves the flame retardancy of lithium-sulfur batteries and reduces the self-extinguishing time of the electrolyte through radical elimination mechanism. Oxygen-containing flame retardants exhibit a stronger adsorption capacity and are more advantageous in mitigating the shuttle effect and enhancing the cycle and rate performance of the batteries. This simple coating strategy offers a competitive option for large-scale production of high-safety lithium-sulfur batteries.