Spatially Engineered Janus Separator Enables Bidirectional Regulation of Sulfur Electrochemistry and Lithium Deposition in High‐Energy‐Density Lithium–Sulfur Pouch Cells

Abstract Lithium–sulfur (Li–S) batteries are promising candidates for energy storage applications. However, their practical implementation is impeded by significant challenges, including the polysulfide shuttle and the pulverization of the lithium anode. Herein, this study presents an interfacial engineering through the development of a bifunctional separator based on polymer of intrinsic microporosity (PIM‐1). On the cathode side, the aminated PIM‐1 framework (APIM) establishes a dual physical–chemical regulation mechanism. Its rigid nanoporous structure facilitates the sieving of polysulfides through size exclusion, while the functionalized surface induces electrostatic repulsion and chemisorption to suppress polysulfide shuttling.This configuration simultaneously ensures unobstructed Li + transport. At the anode interface, the lithium hydroxycarboxylate PIM‐1 (LCPIM) optimizes the Li + flux by refining the microporous architecture, enhancing Li + binding‐desorption, and homogenizing ion migration pathways. This dual‐functional architecture addresses the challenges of active material shuttling and interfacial degradation of anodes by simultaneously regulating ion flux and stabilizing dual electrodes. This approach achieves a Coulombic efficiency exceeding 99.7% and maintains capacity retention over 600 cycles. Janus separators demonstrate viability in 3 Ah pouch cells (9.6 mg cm −2 sulfur loading, double‐sided, Electrolyte/Sulfur = 3.3), achieving 373 Wh kg −1 energy density at 0.2 C and demonstrating stable operation over 40 cycles.