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.