Ni-doped Fe-MOF@rGO nanohybrid as a functional separator for ultra-long cyclability in lithium-sulfur cells

The slow conversion kinetics of polysulfides and undesired shuttling behavior significantly limit the practical feasibility of lithium-sulfur (Li-S) batteries. In light of this, a functional separator made of a composite material consisting of nickel/iron metal-organic frameworks supported on reduced graphene oxide (Ni/Fe-MOF@rGO) with numerous defects is proposed to produce heightened-performance Li-S batteries. Ni-doping Fe-MOF can improve the Li-S cell's electrochemical performance during charge-discharge cycles by increasing the number of metallic sites on the surface, enhancing electrical conductivity, and improving metal synergy. As a result of chemical interaction and physical adsorption, the polysulfide shuttle effect is diminished. Thus, the Li-S cell with electrocatalytic separators of Ni/Fe-MOF@rGO-PP generates 735, 678, 590, 431, and 403 mAh g⁻¹ after 250, 500, 750, 1000, and 1250 cycles, respectively, at 1.0 C, validating the low-capacity degradation per cycle with high long-cyclic. Furthermore, when the cell is operated under harsh conditions (4.3 mg_sulfur cm⁻² and electrolyte/sulfur (E/S) ratio is 7.0 µL mg⁻¹), the resulting capacity is still outstanding even after multiple charge and discharge cycles (4.0 mAh cm⁻² after the 250th cycle). This implies that the utilization of Ni/Fe-MOF@rGO has the potential to function as an improved separator within commercially available Li-S cells.