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

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_0.8Co_0.1Mn_0.1O₂ 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.