The main challenges facing Li-S batteries stem from the low conductivity of sulfur and the dissolution of lithium polysulfides. This study addresses these issues by synthesizing Fe3C@C nanofibers through electrospinning followed by heat treatments, which are then applied as an interlayer in Li-S cells. The pre-oxidation temperature is adjusted to achieve the desired material properties, in which Fe3C nanoparticles are embedded in graphitic carbon nanofibers, resulting in a high specific surface area and mesopore volume. This configuration provides excellent polysulfide adsorption and catalytic properties for their further conversion. Consequently, when used as an interlayer, the electrochemical performance of the cell, including discharge capacity (first: 1174.1 vs. 850 mAh g−1 at 0.1C), stability (852.4 vs. 400 mAh g−1 after 100 cycles), and rate-capability (620 vs. 100 mAh g−1 at 2C), is significantly enhanced compared to cells without interlayer.