Controlling the polysulfide diffusion in lithium-sulfur batteries with a polymer membrane with intrinsic nanoporosity

Abstract

Polysulfide-shuttle has been a critical concern for the advancement of lithium-sulfur (Li-S) batteries. Celgard membranes that are generally used in Li-S batteries exhibit a porous structure with a pore dimension generally on the micrometer scale. During cell operation, soluble lithium polysulfide species can easily migrate from the cathode through the porous separator and react with the lithium-metal anode. Such an unexpected chemical reaction induces a cascade of negative effects on the overall performance of Li-S batteries. Use of ion-selective membranes with reduced pore size provides a promising approach to suppress the migration of polysulfide species. In this study, a membrane based on a polymer with intrinsic nanoporosity (PIN) with a pore size of <1.0 nm is explored as a separator in Li-S batteries to mitigate the polysulfide-shuttle problem. The PIN membrane exhibits a unique structure with pore dimensions of less than 1.0 nm, which allows the transport of Li-ions, but effectively blocks the migration of dissolved polysulfides. As a result, the cycling performance of Li-S batteries is significantly improved. In addition to demonstrating a PIN-membrane Li-S battery, the structural characteristics of the PIN membrane have been characterized by a series of experimental methodologies and molecular dynamics (MD) simulations.