Constructing Ion-Selective Coating Layer with Lithium Ion Conductor LLZO and Binder Li-Nafion for Separator Used in Lithium-Sulfur Batteries

In the study of lithium-sulfur batteries, the shuttle effect of polysulfide ions is widely regarded as the most critical factor in the battery performance deterioration. In this article, with the strategy of ion-selection, a method of preparing a coating layer with solid-phase conduction for a separator was used to suppress such an effect. The coating layer was based on calcined ceramic Li7La3Zr2O12 (LLZO) and formed through a simple coating method to be thin but dense. The gap between particles was filled with lithiated Nafion (Li-Nafion) which could block polysulfide ions through coulombic interactions of sulfonate groups and allowed the lithium ion conduction. The properties of compactness and the ion-selection formed a double barrier effect, manifested as the fact that the estimated lithium ion transport number achieved 0.79. Correspondingly, the lithium-sulfur batteries assembled with the ion-selective conduction separators had better lithium deposition behavior and exhibit brilliant cycling performances and capacity retention.