A functional separator comprised of agglomerates of the ferroferric oxide (Fe3O4) nanoparticles and carbon coating, bonded together with carbon nanotube (CNT) is designed to enhance the electrochemical performance of Lithium/sulfur (Li/S) batteries. The strong interaction between polar Fe3O4 and lithium polysulfides effectively prevents the shuttling effect. Porous carbon coating layer and CNT network are further introduced into Fe3O4 nanoparticles to enlarge the specific surface area of the composite, improve its electronic conductivity, and boost the kinetic reactions. The confinement of polysulfides by Fe3O4 is supported by the results of density functional theory (DFT) calculations. Specifically, the Li/S cells exhibit an initial discharge capacity as high as 1542 mAh g-1 at 0.2 C, retain a long-term cyclability of 651 mAh g-1 at 1 C after 1000 cycles, and deliver a superior rate capability of 653 mAh g-1 even at 5 C. Notably, the cells with the carbon nanotube/Fe3O4 coated by carbon (CNT/Fe3O4@C) modified separator with high sulfur loading can also exhibit superior cycling performance, deliver a high areal capacity of 4.4 mAh cm-2 over 60 cycles. The present work provides a facile method for making Li/S batteries commercially viable.