A porous carbon structure (PCS) is considered as an ideal electrode material for lithium–sulfur (Li–S) batteries, owing to its flexible texture, large surface area, and high electrical conductivity. In this work, we use food-grade yeast as the carbon precursor, which is proliferated in glucose solution, carbonized with a NaCl template to yield a sheet-like carbon structure, and reactivated at different temperatures with KOH. The porous carbon material is then applied as the sulfur host of the Li–S battery cathode, and the electrode is systematically characterized by means of SEM, TEM, XRD, Raman, XPS, thermogravimetric (TG), nitrogen gas adsorption–desorption, and electrochemical measurements. The results show that the PCS obtained at 800 °C has an ultra-high surface area of 2410 m2 g−1 and exhibits excellent performance for a Li–S battery cathode. The initial discharge capacity of the PCS-800/S cathode is 1502 mAh g−1, which accounts for 90% of the theoretical capacity value.