High sulfur loading and long cycle life are the design targets of commercializable lithium–sulfur (Li–S) batteries. The sulfur electrochemical reactions from Li2S4 to Li2S, which account for 75% of the battery's theoretical capacity, involve liquid‐to‐solid and solid‐to‐solid phase changes in all Li–S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li2S4 to Li2S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott−Schottky junction of the heterostructure can facilitate charge transfer in the Li2S4 to Li2S2 liquid‐to‐solid reaction and Li+ diffusion in the Li2S2 to Li2S solid‐state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g−1 at the sulfur loading of 6 mg cm−2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8 mg cm−2 for 440 cycles at the 1 C rate. [ABSTRACT FROM AUTHOR]