In Situ Polymerization of Ultra‐Thin and Defect‐Free Polyamide Layer for Effectively Impeding the Polysulfides Shuttle

Abstract Lithium‐sulfur (Li‐S) batteries present significant potential for next‐generation high‐energy‐density devices. Nevertheless, obstacles such as the polysulfide shuttle and Li‐dendrite growth severely impede their commercial production. It is still hard to eliminate gaps between individual particles on separators that serve as potential conduits for polysulfide shuttling. Herein, the synthesis of a nanoscale thickness and defect‐free cross‐linked polyamide (PA) layer on a polypropylene (PP) separator is presented through in situ polymerization. The PA modification layer can effectively impede the diffusion of polysulfides with a thickness of only 1.5 nm, as evidenced by the results of cyclic voltammetry (CV) and time‐of‐flight (TOF) testing. Therefore, the Li/Li symmetric battery assembled with the functional separator exhibits an overpotential of merely 12 mV after 1000 h of cycling under test conditions of 1 mA cm⁻²‐1 mAh cm⁻². Furthermore, the capacity degradation rate of the Li‐S battery is only 0.06% per cycle over 450 cycles at 1 C, while the Li‐S pouch cell retains 87.63% of its capacity after 50 cycles. This work will significantly advance the preparation and application of molecules in Li‐S batteries, and it will also stimulate further research on defect‐free modification of separators.