Co-based and Cu-based MOFs modified separators to strengthen the kinetics of redox reaction and inhibit lithium-dendrite for long-life lithium-sulfur batteries

In this study, two kinds of MOFs nanoparticles including ZIF-67 and Cu-BTC (HKUST-1) were synthesized and the MOFs modified gel F-doped poly-m-phenyleneisophthalamide (PMIA) nanofiber membranes were successfully prepared through blend electrospinning of these synthesized MOFs nanoparticles and PMIA solution. And the electrochemical performance and safety for Li-S cells with the MOFs modified gel PMIA nanofiber separators were systematically researched. Under the synergistic role of F-doped emulsion and MOFs nanoparticles, the modified PMIA-based membranes can produce relatively high porosity, reduced aperture and good electrolyte uptake. And the merits endow the separator with prominent thermal stability, mechanical strength and ionic conductivity, which lays a solid footing stone for high-performance and advanced-safety Li-S battery with fast ion transportation, reduced polarization, good interfacial compatibility and strong catalysis. The batteries with ZIF-67 and Cu-BTC (HKUST-1) modified membranes exhibited high first-cycle discharge capacity of 1267.5 and 1272.2 mAh g(-1), outstanding discharge capacity retention of 698.1 and 752.6 mAh g(-1) and super-high Coulombic efficiency of 99.75% and 99.82% after 500 cycles at 0.5 degrees C rate, respectively. The outstanding electrochemical properties and safety for the batteries assembled were ascribed to the greatly prevented "shuttle effect" of dissolved lithium polysulfides based on the physical capturing of high-order lithium polysulfides via the prepared jelly-like gel state and strongly chemical adsorbing to lithium polysulfides, and fast redox kinetics based on the strong catalytic conversion. This work proves that the addition of functional MOFs nanoparticles similar with ZIF-67 and Cu-BTC (HKUST-1) in gel F-doped PMIA membrane can inhibit the "shuttle effect" of polysulfides and reduce the growth of lithium dendrites to some extent, which will prompt a great development of Li-S battery with high performance and reassuring safety.