Flame-retardant and thermal-stable separator trapping polysulfides for lithium-sulfur battery

The shuttle effects of polysulfides and abominable safety problems restrict the practical application of lithium-sulfur batteries. Herein, we report a polyimide-based Janus separator by a simple filtration method introducing MoO3 nanoparticles and MWCNTs-COOH. Using this separator, the lithium-sulfur battery delivers a reversible capacity of 1274 mA h g−1 at 0.2 C and a capacity 637 mA h g−1 at 5 C. Moreover, the separator is flame-retardant and thermal-stable without obvious shrinkage even at 300 °C. Experimental observations reveal that uniformly dispersed MoO3 nanoparticles and MWCNTs-COOH as a pore structure regulator can obviously decrease the pore diameter and porosity of electrospun polyimide (PI) skeleton for intercepting polysulfides. The synergistic effect between MWCNTs-COOH, MoO3 and polyimide fibers enables the faster kinetics and more efficient conversion of polysulfides.