Charge‐Tunable Coacervate Micelles for Separator Engineering in Lithium‐Sulfur Batteries

ABSTRACT The growing demand for high‐energy‐density storage in renewable energy and electric mobility applications has renewed interest in lithium‐sulfur (Li‐S) batteries owing to their ultrahigh theoretical specific energy, low cost, and environmental sustainability. However, their practical application remains severely constrained by the polysulfide shuttle effect, which causes self‐discharge and rapid capacity degradation. Here, for the first time, we report a separator modification strategy based on the adsorption of complex coacervate core micelles (C3Ms) that effectively suppresses polysulfide migration while promoting selective Li + transport. The C3Ms consist of an electrostatically assembled poly(acrylic acid)/poly(dimethylaminopropylacrylamide) core stabilized by a hydrophilic poly(N‐isopropylacrylamide)‐based corona, enabling uniform deposition on both the surface and the internal pore walls of commercial polypropylene separators through a simple solution‐based process. The resulting multifunctional coating immobilizes polysulfides via a combination of electrostatic interactions, steric confinement, and chemical adsorption. By tuning the surface charge of the micellar layer, the Li‐S cells equipped with a positively charged C3M‐modified separator exhibit markedly enhanced cycling stability, retaining 63% of the initial capacity after 400 cycles at 0.5 C. This work establishes complex coacervate core micelles as a versatile and scalable platform for separator engineering, providing a practical pathway toward high‐performance and durable lithium–sulfur batteries.