A functional separator coated with sulfonated metal-organic framework/Nafion hybrids for Li-S batteries

A functional separator is designed to improve the utilization of sulfur and to inhibit polysulfide shuttling for high performance lithium-sulfur (Li-S) batteries. Here, we demonstrate a functional separator which is obtained by coating sulfonated UiO-66 metal-organic framework (MOF)/Nafion on a polyethylene separator. This modified separator suppresses the polysulfide diffusion due to a molecular sieving and electrostatic repulsion effect and facilitates the redox kinetics of sulfur conversion because of a fast charge transport by sulfonic groups tethered to the MOF and Nafion. Thus, the Li-S cells based on the MOF/Nafion hybrid-coated separator achieve a discharge capacity of 1127.4 mA h g⁻¹ at 0.1C, a capacity retention of 66.8% at 3C relative to 0.1C, and a cycling stability of 75.5% over 200 charging/discharging cycles. These values are much greater than those of pristine and Nafion-coated separators, which confirms the superiority of MOF/Nafion hybrid coating layers for the design of functional separators.