Heterointerface Engineering for Stepwise Catalysis of Polysulfides in High Sulfur Loading Lithium-Sulfur Batteries

Catalyzing polysulfides conversion is essential for mitigating the shuttle effect and sluggish kinetics in lithium-sulfur (Li-S) batteries, yet single-component catalysts struggle to sustain activity throughout the complex sulfur redox process. Herein, a nanoflower-structured CoS/Co₉S₈ heterojunction derived from a MOF template is designed as an advanced sulfur host. The built-in electric field at the p-n interface facilitates rapid charge transfer and directional migration of polysulfides, while the distinct catalytic properties of CoS and Co₉S₈ enable stepwise conversion of lithium polysulfides from S₈ to Li₂S. Coupled with its hierarchical porous architecture, the host achieves high sulfur loading (84 wt.%) and efficient capture-diffusion-conversion of polysulfides. As a result, the assembled Li-S cell delivers a high discharge capacity of 1295.9 mAh g^-1 at 0.2 C, an ultralow decay rate of 0.069% per cycle over 300 cycles at 2 C, and a remarkable volumetric capacity of 1082.07 mAh cm^-3 under high sulfur mass loading. This work demonstrates a synergistic morphology and interface engineering strategy to realize high-energy-density Li-S batteries with long-term stability.