Lithium–sulfur (Li–S) batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability. The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density. However, the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases. Herein, we used diameters of 5.0 (D5) and 13.0 (D13) mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading (4.5 mg cm−2). The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large (D13) cathode. Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions, which results in inferior battery performance of the Li–S cell with large diameter cathode. This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading, carbon modified separators, organic electrolyte, and Li metal anode in a pouch cell, wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.