Lithium Metal Batteries Enabled by Ion Flux‐Regulating Coating on Separator

Abstract Separator modification is a facile approach for ensuring stable cycling of lithium metal batteries. Here, a hybrid polymer coated separator with high Young's modulus and ion conductivity is designed by integrating proton‐doped polyaniline (PANi) nanosheets with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP). Density functional theory (DFT) calculation confirms that the proton‐doped PANi nanosheets interact with TFSI ⁻ anions and its 2D confinement effect induces conformational transition of PVDF to the polar β phase. These synergistic effects optimize Li ⁺ transport. Besides, finite element simulations and in situ optical microscopy indicate that the conjugated structure of PANi promotes electron delocalization and homogenizes the potential across lithium anode surface, guiding a uniform Li ⁺ flux and dense lithium deposition. Moreover, the hybrid polymer coating leads to the formation of LiF‐enriched SEI on lithium metal surfaces. As a result, Li||Li symmetric batteries with the hybrid polymer coated separator exhibit stable cycling for over 2000 h at a current density of 10 mA cm⁻ ² . In additoin, Li||LFP batteries using the modified separator has a stable cycling for over 200 cycles at 3 C, maintaining a capacity of 99.25 mAh g⁻¹ with a high areal loading of 13.5 mg cm⁻ ² .