Li–S batteries are regarded as one of the most promising energy-storage devices due to their high theoretical energy density, five times higher than that of lithium-ion batteries (2600 vs. ∼500 W h kg⁻¹). However, the polysulfide shuttle effect is the primary challenge for future applications of Li–S batteries. Herein, a novel barrier layer material, nonstoichiometric W₁₈O₄₉ nanowires, is reported to alleviate the undesirable shuttle effect, thereby largely boosting the specific capacity and cyclability of Li–S batteries. Without particular cathode design, the introduction of W₁₈O₄₉ nanowires enables the commercially available micro-sized sulfur cathode with 70% sulfur loading to deliver a respectable initial discharge capacity of 1142 mA h g⁻¹ and retain a specific capacity of about 809 mA h g⁻¹ after 50 cycles, even at a current density of 0.5 A g⁻¹. To the best of our knowledge, such a capacity fading for Li–S batteries based on high loading of commercial micro-sized sulfur has been rarely reported.