Suppressing shuttle effect by large oxygen-containing crosslinked hyperbranched polyurethane as cathode encapsulated layer for high-performance lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries have attracted a lot of attention because of their high energy density, low cost, and environmental friendliness. However, shuttle effect is one of the most obstacles to make the poor cycling performance and inhibit the development of Li-S batteries. Herein, a kind of large oxygen-containing polymer coated cathode, named polyurethane coated carbon-nanotube/sulfur composites (PU@S-CNT), is prepared from sulfur capsulated by the reaction of hyperbranched polyether and diisocyanate via a simple “one-pot” strategy to impede the shuttle effect. This PU@S-CNT cathode can not only inhibit the dissolution of lithium polysulfides by physical barrier, but also can absorb the lithium polysulfides by the chemical effect. Especially, the cell with PU@S-CNT electrode shows an excellent initial cycling capacity of 892 mAh g−1 at 2C and remarkable capacity retention (a low decay rate of 0.051% per cycle at 2C after 450 cycles). More importantly, this coated cathode (PU@S-CNT) demonstrates a good inhibition of shuttle effect, high transmission speed of lithium ion and good cycle reversibility. This work exhibits the cross-linked hyperbranched polyurethane is used as coatings of the sulfur cathode for the first time, which can reveal a potential prospect of high-level heteroatom doped coated cathodes for high-performance lithium-sulfur batteries.