Lithium–sulfur batteries (LSBs) are promising alternative energy storage devices to the commercial lithium-ion batteries. However, the LSBs have several limitations including the low electronic conductivity of sulfur (5 × 10−30 S cm−1), associated lithium polysulfides (PSs), and their migration from the cathode to the anode. In this study, a separator coated with a Ketjen black (KB)/Nafion composite was used in an LSB with a sulfur loading up to 7.88 mg cm−2 to mitigate the PS migration. A minimum specific capacity (C s) loss of 0.06% was obtained at 0.2 C-rate at a high sulfur loading of 4.39 mg cm−2. Furthermore, an initial areal capacity up to 6.70 mA h cm−2 was obtained at a sulfur loading of 7.88 mg cm−2. The low C s loss and high areal capacity associated with the high sulfur loading are attributed to the large surface area of the KB and sulfonate group (SO3 −) of Nafion, respectively, which could physically and chemically trap the PSs.