Functional separator, which bridges anode, electrolyte and cathode together, has the potential to offer a good solution for efficient polysulfide diffusion inhibition and anode protection of Li-S battery. Herein, a novel ultra-thin multifunctional separator is prepared by a facile coating of colloidal dispersion of Nb2O5 /reduced graphene oxide nanocomposites (rGO) onto porous polypropylene (PP) matrix. Benefiting from the physical blocking effect of rGO layer and chemisorption of Nb2O5, the shuttle of polysulfides has been greatly suppressed. Meanwhile, the rGO layer functioning as a conductive upper current collector can improve the sulfur utilization, while the Nb2O5 with high activity promotes the transformation of sulfur-containing species. With the assistant of Nb2O5-rGO function layer, the sulfur cathode shows significantly improved electrochemical performance with a high specific capacity of 1328 mAh g(-1) at 0.2C and 754 mAh g(-1) retained after 200 cycles. The sulfur cathode also exhibits excellent rate capability and stable Coulombic efficiency of 91% without the addition of LiNO3 in the electrolyte. Moreover, the presence of thin Nb2O5-rGO layer also prevents the lithium surface corrosion and the dendrite growth in the lithium anode. (C) 2020 Published by Elsevier Inc.