Bimetallic Metal-Organic Framework with High-Adsorption Capacity toward Lithium Polysulfides for Lithium–sulfur Batteries

The practical application of Li-S batteries is largely impeded by the "shuttle effect" generated at the cathode which results in a short life cycle of the battery.To address this issue,this work discloses a bimetallic metal-organic framework（MOF） as a sulfur host material based on AI-MOF,commonly called（AI）MIL-53.To obtain a high-adsorption capacity to lithium polysulfides（Li2 Sx,4 ≤x≤8）,we present an effective strategy to incorporate sulfiphilic metal ion（Cu2+） with high-binding energy to Li2 Sx into the framework.Through a one-step hydrothermal method,Cu2+ is homogeneously dispersed in AI-MOF,producing a bimetallic AI/Cu-MOF as advanced cathode material.The macroscopic Li2S4 solution permeation test indicates that the AI/Cu-MOF has better adsorption capacity to lithium polysulfides than monometallic AI-MOF.The sulfur-transfusing process is executed via a melt-diffusion method to obtain the sulfur-containing Al/CuMOF（AI/Cu-MOF-S）.The assembled Li-S batteries with Al/Cu-MOF-S yield improved cyclic performance,much better than that of monometallic AlMOF as sulfur host.It is shown that chemical immobilization is an effective method for polysulfide adsorption than physical confinement and the bimetallic Al/Cu-MOF,formed by incorporation of sulfiphilic Cu2+ into porous MOF,will provide a novel and powerful approach for efficient sulfur host materials.