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Lithium–sulfur (Li–S) batteries are considered a promising next generation alternative to lithium-ion batteries for energy storage systems due to its high energy density. However, several challenges, such as the polysulfide redox shuttle causing self-discharge of the battery, remain unresolved. In this paper, we explore the use of polymer etched ion-track membranes as separators in Li–S batteries to mitigate the redox shuttle effect. Compared to commercial separators, their unique advantages lie in their very narrow pore size distribution, and the possibility to tailor and optimize the density, geometry, and diameter of the nanopores in an independent manner. Various polyethylene terephthalate membranes with diameters between 22 and 198 nm and different porosities were successfully integrated into Li–S coin cells. The reported coulombic efficiency of up to 97% with minor reduction in capacity opens a pathway to potentially address the polysulfide redox shuttle in Li–S batteries using tailored membranes.