Ultrathin Cobalt Phthalocyanine@Graphene Oxide Layer-Modified Separator for Stable Lithium–Sulfur Batteries

Rechargeable lithium-sulfur (Li-S) batteries have aroused great attention due to their high energy density and low cost. However, Li-S batteries suffer from rapid capacity decay owing to the shuttle effect of the intermediate polysulfides. To tackle this issue, functional separators with the ability to absorb polysulfides play a vital role to block them from passing through the separator. Herein, an ultrathin and lightweight layer of graphene oxide (GO) loaded with Co phthalocyanine (CoPc) is fabricated on a polypropylene (PP) separator. The thickness of CoPc@GO is about 200 nm with a low areal mass of 22 μg cm-2. CoPc is uniformly dispersed on GO sheets through π-π interactions, which inhibits the shuttle effect and facilitates the conversion of the intermediate polysulfides. In consequence, the battery with a CoPc@GO-PP separator exhibits good cycling stability with a low-capacity decay rate of 0.076% per cycle at 1 C over 400 cycles and a high specific capacity of 919 mA h g-1 after 250 cycles at 0.5 C.