Mitigating Concentration Polarization via Ion‐Sieving Interlayer Towards Long‐Life 510 Wh Kg −1 Lithium Metal Pouch Cells

Abstract Uncontrolled transport of lithium‐ion and anion induce concentration polarization and Li dendrite growth, severely hindering the development of high‐energy‐density Li‐metal batteries, especially under high current densities (≥3 mA cm −2 ). Herein, we report an interfacial ion‐sieving strategy to immobilize anions and guide uniform lithium‐ion transport for stable Li‐metal batteries by introducing a poly(2‐acryloyloxyethyltrimethylammonium chloride‐co‐polyethylene glycol monomethyl ether methacrylate) (PAP) interlayer on Li metal anode. The quaternary ammonium groups effectively anchor anions and suppress their migration, while polyether chains facilitate homogeneous lithium‐ion transport and diffusion. This synergistic effect increases the lithium‐ion transference number, mitigates interfacial concentration polarization, and inhibits dendrite growth even at 5 mA cm −2 . Impressively, we demonstrate a 7 Ah PAP‐Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 pouch cell with ultra‐high energy density (510 Wh kg −1 ) and remarkable capacity stability (84.2%, 180 cycles), even under lean electrolyte (1.19 g Ah −1 ) and high current density (3 mA cm −2 ). Our findings highlight the potential of ion‐sieving interlayer as a promising strategy for the development of stable Li‐metal batteries.