PPy-constructed core–shell structures from MOFs for confining lithium polysulfides

Abstract

For sulfur host materials in Li–S batteries, the structure is important for suppressing the shuttle effect and buffering the volume expansion. A polypyrrole (PPy)-coated core–shell structure is obtained with porous MIL-96-Al as the skeleton by a melt-diffusion method and a water-phase polymerization process, named as MIL-96-S-PPy. The strong chemical interaction between the lithium polysulfides (LPS) and the PPy shell can prevent the diffusion of LPS from the cathode to the anode. The electron-rich PPy shell can bond with electropositive Li⁺ in LPS by a polar–polar interaction and buffer the volume expansion. Moreover, the porous MIL-96-Al can provide free space for sulfur impregnation, resulting in improved coulombic efficiency and sulfur utilization. With the help of the PPy-coated core–shell structure, the initial specific capacity could achieve 1233.8 mA h g⁻¹ at 0.5 C. This work provides a new perspective to design a core–shell structure as a high-performance sulfur cathode for advanced Li–S batteries.