Efficient separators with fast Li-ion transfer and high polysulfide entrapment for superior lithium-sulfur batteries

Abstract

A facile and general vacuum-filtration approach is employed to coat hierarchical metal–organic framework-derived Co-C polyhedrons onto traditional separators for lithium − sulfur batteries. The resultant condensed separators with Co-C coating (Co-C@separator) can effectively decrease the pore size of commercial separators from 200 to 300 nm to 2.2–10 nm. The decreased pore sizes block the shuttling of lithium polysulfides (LiPSs) through the separator, thus solving the annoying ‘shuttle effect’ via physical confinement. Furthermore, the embedded Co nano-nodes in Co-C polyhedrons are capable of capturing LiPSs via strong chemical adsorption of soluble LiPSs. Through this advantage combined with the rapid Li-ion transport through the intragranular pores between the Co-C polyhedrons, a sulfur-rich cathode (72% sulfur) has achieved outstanding performance when using the Co-C@separator, delivering decent cycling stability (675 mAh g−1 after 300 cycles at 0.1 A g−1) and high rate performance (401 mAh g−1 after 600 cycles at 1.0 A g−1). This approach serves as a facile strategy for remedying the shuttle phenomenon in lithium-sulfur batteries.