A facile method that improves the initial specific capacity and capacity retention rate of lithium-sulfur (Li-S) batteries, using silica-back-coated nickel foam has been studied. A new cathode collector in which silica is back-coated onto the nickel foam is fabricated by a facile method that utilizes an ultrasonicator for reducing the electrolyte viscosity at the surface of the sulfur electrode using a polysulfide absorbent. The nickel foam provides more reaction sites than an aluminum current collector does, thus allowing the back-coated silica to absorb the polysulfides. This synergetic effect of nickel foam and silica suppresses the increasing viscosity of the electrolyte and leads to a higher initial specific capacity (1341 mAh/g) at a 0.2-C rate and a higher capacity retention rate after 150 cycles (85%), relative to pristine Li-S batteries (951 mAh/g and 79%, respectively).