Alloy‐Regulated Heterointerface Engineering for Kinetics‐Driven Sulfur Redox in Li‐S Batteries

Lithium‐sulfur (Li‐S) batteries offer exceptional theoretical energy density, yet their practical deployment is fundamentally constrained by sluggish sulfur redox kinetics and persistent shuttle of polysulfides. Here, we report a NiMo‐alloy‐assisted quantitative heterointerface engineering strategy that regulates the phase balance, interfacial abundance, and electronic coupling in Mo 2 C/MoC heterostructures. By tuning the Ni/Mo ratio as a continuous control parameter, NiMo incorporation drives controlled Mo 2 C→MoC phase reconstruction to maximize the density and accessibility of catalytically active Mo 2 C/MoC heterointerfaces, while the resulting NiMo domains primarily function as a structural modulator and metallic electron‐transport pathway, complementing the conductive nitrogen‐doped carbon framework. In situ/ex situ characterizations and density functional theory calculations reveal Mo 2 C/MoC heterointerfaces intrinsically exhibit the most favorable polysulfide adsorption strength and the lowest energy barriers for bidirectional sulfur conversion. As a result, Li‐S cells equipped with the catalytic separator deliver a high reversible capacity of 1477.8 mAh g −1 at 0.1 C and sustain long‐term cycling with an ultralow decay rate of 0.032% per cycle over 1000 cycles at 0.5 C, enabling an areal capacity of 15.2 mAh cm −2 at high sulfur loading. This work establishes a quantitative heterointerface design paradigm for regulating sulfur electrochemistry and provides general insights into heterostructure‐enabled catalysis in metal‐sulfur batteries.