Amorphous bimetallic-organic framework enable accelerated redox kinetics and polysulfide trapping for lithium-sulfur batteries

Severe polysulfide dissolution and shuttling during charging and discharging are the main challenges hindering the practical application of lithium-sulfur (Li-S) batteries. Constructing functional separators is considered as an economical and convenient way to suppress the shuttle effect and improve the kinetics of Li-S chemistry. In this work, partially ligand-deficient amorphous bimetallic MOF material (aFeNi-MOF) is designed via a ligand competition strategy and employed as a separator modifier. The aFeNi-MOF not only promotes the rapid transportation of ions, but also enhances the chemisorption and catalytic capability on sulfur species, enabling accelerated redox kinetics and polysulfide trapping in Li-S batteries. Consequently, the assembled coin cell using aFeNi-MOF-modified separator delivered a high reversible capacity of 931.1 mAh/g at 1C, a long cycle life of more than 500 cycles and a low capacity decay of 0.084 % per cycle. Meanwhile, the areal capacity of 3.70 mAh cm−2 can be achieved under a high sulfur loading of 4.5 mg cm−2 and low electrolyte usage, meeting the requirement of areal capacity for commercial applications of Li-S batteries.