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Lithium−sulfur batteries have great potential in the field of next-generation energy-storage devices owing to their high theoretical energy density. However, the polysulfide intermediates shuttling seriously result in fast capacity degradation and poor cycling stability, thus hindering their commercial applications. In this paper, we choose polyvinylidene fluoride containing polar functional groups in its polymeric chain as polymer carrier to construct the H 3 PW 12 O 40 firmly and uniformly decorated nanofibers membrane by electrospinning technique. Benefiting from the feature of "electron sponges", H 3 PW 12 O 40 can act as polysulfide mediator to significantly facilitate the liquid-liquid reaction kinetics of polysulfides in the electrode/separator interface. Besides, fewer cracks, pulverization and adhesion of dead lithium particles occurred in the lithium metal anode, demostrating a more homogeneous Li-ion flux distribution after using this membrane with three-dimensional network structure and abundant redox active sites. The cell with such bifunctional separator delivers a specific capacity of 966 mAh g−1 at 1.0 C, and retained a capacity of 682 mAh g−1 after 300 cycles, corresponding to an average capacity loss of 0.09% per cycle. [Display omitted] • The PW 12 -PVDF/PP separator could regulate the Li+ flux to induce Li nucleation. • The PW 12 -PVDF/PP separator improves the catalytic effect of the polysulfides. • The Li–S cell with PW 12 -PVDF/PP separator shows good electrochemical performances. [ABSTRACT FROM AUTHOR]