Synergetic effect of block and catalysis on polysulfides by functionalized bilayer modification on the separator for lithium-sulfur batteries

Abstract

One crucial problem hindering the commercial application of lithium-sulfur batteries with high theoretical specific energy is the ceaseless shuttle of soluble lithium polysulfides (LiPSs) between cathodes and anodes, which usually leads to rapid capacity fade and serious self-discharge issues. Herein, a unique bilayer coating strategy designed to modify the polypropylene separator was developed in this study, which consisted of a bottom zeolite (SSZ-13) layer serving as a LiPS movement barrier and a top ZnS layer used for accelerating redox processes of LiPSs. Benefiting from the synergetic effect, the bilayer-modified separator offers absolute block capability to LiPS diffusion, moreover, significant catalysis effect on sulfur species conversion, as well as outstanding lithium-ion (Li+) conductivity, excellent electrolyte wettability, and desirable mechanical properties. Consequently, the assembled lithium-sulfur cell with the SSZ-13/ZnS@polypropylene separator demonstrates excellent cycle stability and rate capability, showcasing a capacity decay rate of only 0.052% per cycle at 1 C over 500 cycles.