Cross‐Linked Amine Interface Engineering Strategy for High Performance Anode‐Free Lithium‐Metal Batteries With High‐Loading Cathodes

ABSTRACT Anode‐free lithium‐metal batteries (AFLMBs), wherein Li is plated onto a bare Cu current collector during the initial charge, feature a simplified architecture and high energy density. However, in AFLMBs employing high‐mass‐loading cathodes, the intrinsically poor lithiophilicity of bare Cu induces uncontrolled dendrite growth, irreversible lithium loss, and an unstable solid electrolyte interphase (SEI), resulting in rapid capacity decay and a low Coulombic efficiency (CE). Herein, an ultrathin, cross‐linked polyethylenimine (PEI) coating is proposed as a simple yet effective interfacial engineering strategy to stabilize the anode–electrolyte interface through dual mechanisms. Abundant amine groups coordinate strongly with Li⁺, promoting homogeneous nucleation and vertical deposition while restricting lateral diffusion. The flexible polymer matrix acts as a robust barrier against parasitic reactions and corrosion. Consequently, Cu||Li half‐cells with PEI‐coated Cu sustain 350 cycles at 0.5 mA cm −2 and 0.5 mAh cm −2 , delivering an average CE of 95.29%. Full cells with high‐loading LiFePO 4 cathodes (26.52 mg cm −2 ) retain 57.65% of their initial capacity (3.26 to 1.87 mAh cm −2 ) after 100 cycles. These findings highlight nanoscale polymer coatings as a promising strategy for constructing stable artificial SEI layers in AFLMBs, yielding high‐energy and durable Li‐ion batteries.