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

Abstract

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 Al‐MOF, commonly called (Al)MIL‐53. To obtain a high‐adsorption capacity to lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8), we present an effective strategy to incorporate sulfiphilic metal ion (Cu 2+ ) with high‐binding energy to Li 2 S x into the framework. Through a one‐step hydrothermal method, Cu 2+ is homogeneously dispersed in Al‐MOF, producing a bimetallic Al/Cu‐MOF as advanced cathode material. The macroscopic Li 2 S 4 solution permeation test indicates that the Al/Cu‐MOF has better adsorption capacity to lithium polysulfides than monometallic Al‐MOF. The sulfur‐transfusing process is executed via a melt‐diffusion method to obtain the sulfur‐containing Al/Cu‐MOF (Al/Cu‐MOF‐S). The assembled Li‐S batteries with Al/Cu‐MOF‐S yield improved cyclic performance, much better than that of monometallic Al‐MOF 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 Cu 2+ into porous MOF, will provide a novel and powerful approach for efficient sulfur host materials.