CoSn Alloy-based Three-dimensional Ordered Multistage Porous Composite towards Effective Polysulfide Confinement and Catalytic Conversion in Lithium‐Sulfur Batteries

ABSTRACT Reasonable design of porous sulfur cathode can inhibit shuttle effect of lithium polysulfide (LiPS), accelerate redox kinetic and enhance the cycling stability, which is important to the development of lithium-sulfur (Li-S) battery. In this work, a multistage porous composite with three-dimensionally ordered macroporous (3DOM) CoSn alloy and embedded microporous Co decorated N-doped carbon (Co-NC)is rationally designed. The conductive CoSn alloy skeleton exhibits strong polar adsorption and effective catalytic activity towards polysulfide conversion, as well as fast electron transportation. Meanwhile, the 3DOM structure possesses sufficient volume space for ion migration and sulfur expansion. Additionally, the properly embedded Co-NC derived from ZIF-67 can offer abundant micropores and catalytic sites, promoting polysulfide trapping and LiPS conversion kinetics. Accordingly, the Li-S batteries fabricated with 3DOM Co-NC@CoSn exhibit remarkable stability with an ultralow capacity decay of 0.046 % per cycle over 500 cycles at 1 C. An impressive areal capacity of about 5.1 mAh cm−2 under high sulfur loading of 6.8 mg cm−2 is also achieved at 0.2 C, with a high capacity retention of 79 % over 100 cycles. The pouch cell maintains stable at 0.05 C, and the capacity decay is only 0.29 % per cycle. This design and synthesis strategy of cathodes has great prospects in the practical application of Li-S battery.