A polymeric nanocomposite interlayer as ion-transport-regulator for trapping polysulfides and stabilizing lithium metal

Inserting an interlayer between cathode and separator represents a feasible approach for potentially addressing two severe issues in lithium-sulfur batteries: diffusion of polysulfides and growth of lithium dendrites. Thus far, there is a lack of cost-effective strategies to fabricate and characterize the interlayers, as well as a comprehensive understanding of their roles. Herein, we design, fabricate, characterize and gain understanding of an advanced battery interlayer capable of addressing the above two critical issues simultaneously. This porous-structured interlayer with a design of integrating polysulfide-blocking function, good mechanical properties and good adhesion to separator is fabricated by coating a functional porous polymeric nanocomposite on the separator. These functions/properties are realized via a rational combination of two polymers (a "functional" polymer of ultra-high molecular weight poly(ethylene oxide) and a "structural" polymer of poly(vinylidene fluoride)) with conductive fillers. The synergistic effect from the two polymers and the resulting porous structure make the interlayer an excellent ion-transport-regulator, which can benefit trapping the dissolved polysulfides, and more importantly, improve the stability of the lithium metal anode. Further, through comprehensive characterizations on the interlayer, the structure-property-performance relationships for the multifunctional interlayer are established, which favors the development of advanced energy storage devices pursuing controllable and express ion-transport between two electrodes.