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Lithium–sulfur (Li–S) batteries suffer from sluggish sulfur redox reactions under high-sulfur-loading and lean-electrolyte conditions. Herein, a typical Co@NC heterostructure composed of Co nanoparticles and a semiconductive N-doped carbon matrix is designed as a model Mott–Schottky catalyst to exert the electrocatalytic effect on sulfur electrochemistry. Theoretical and experimental results reveal the redistribution of charge and a built-in electric field at the Co@NC heterointerface, which are critical to lowering the energy barrier of polysulfide reduction and Li2S oxidation in the discharge and charge process, respectively. With Co@NC Mott–Schottky catalysts, the Li–S batteries display an ultrahigh capacity retention of 92.1% and a system-level gravimetric energy density of 307.8 Wh kg–1 under high S loading (10.73 mg cm–2) and lean electrolyte (E/S = 5.9 μL mgsulfur –1) conditions. The proposed Mott–Schottky heterostructure not only deepens the understanding of the electrocatalytic effect in Li–S chemistry but also inspires a rational catalyst design for advanced high-energy-density batteries.