Co-Fe phosphide@graphitic carbon nitride nanosheet modified separator for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is a promising next-generation energy storage devices due to its high theoretical capacity (1675 mAh g-1), environment-friendliness, low cost, and natural abundance. However, the shuttle effect and sluggish kinetics of lithium polysulfides (LiPs) hinder its commercialization. Herein, we report the synthesis of cobalt iron phosphide@graphitic carbon nitride nanosheet (CFP@CN) modified separator for Li-S batteries. The Li-S cell with CFP@CN separator (CFP@CN-PP) exhibits a high specific capacity of 786.4 mAh g-1 at 1 C. Furthermore, the Li-S cell with CFP@CN-PP can still retain a discharge capacity of 528.3 mAh g-1 and a capacity decay rate of only 0.084% per cycle after 650 cycles. And, the Li-S cell with CFP@CN-PP maintains high coulombic efficiency above 99% after 650 cycles. These results indicate that the CFP@CN with a large specific surface can alleviate the shuttle effect by strong chemical interaction with lithium polysulfides. Furthermore, thanks to high electrical conductivity of CFP@CN, the utilization of sulfur and redox kinetics can be improved. Our study offers useful insights into designing materials for modified separator of lithium-sulfur battery. •Cobalt iron phosphide@graphitic carbon nitride nanosheet (CFP@CN) was synthesized via electrostatic self-assembly.•The CFP@CN modified separator (CFP@CN-PP) for lithium-sulfur battery was prepared using vacuum filtration.•The CFP@CN-PP can alleviate the shuttle effect of lithium polysulfides (LiPs).•The Li-S batteries with CFP@PCN-PP exhibit a high rate and cycling performance.