In Situ Electrochemical Formation of Multifunctional Li₃N/LiF Hybrid Interphase for Stable Lithium Metal Anodes

Lithium (Li) metal anodes face critical challenges of dendritic growth and poor cycling stability, largely due to the inherent trade‐off within the solid electrolyte interphase (SEI) between high ionic conductivity and robust mechanical/electron‐insulating properties. To resolve this dilemma, an anode‐wide, hybrid SEI that synergistically combines a Li 3 N‐rich phase for rapid ion transport with a LiF‐rich phase for mechanical stability and electronic insulation is designed and constructed. This unique interface is achieved via a novel two‐step process: a metallurgical treatment to pre‐seed a 3D lithiophilic scaffold with a Li 3 N precursor, followed by the in situ electrochemical formation of LiF during cycling. This architecture, featuring well‐matched ion/electron transport properties, facilitates the uniform Li plating/stripping kinetics and effectively suppresses dendrite growth. Consequently, the engineered anode demonstrates unprecedented stability, cycling for over 8000 h in a symmetric cell. In a full‐cell configuration, it maintains ≈93.1% of its capacity after 1000 cycles at a high rate of 10 C. Furthermore, an assembled pouch cell delivers a specific discharge capacity of ≈100 mAh g −1 after 300 cycles. This work presents a powerful strategy of combining metallurgical pre‐seeding with electrochemical formation to engineer multi‐functional, bulk‐integrated interfaces, paving the way for high‐rate, long‐cycling lithium metal batteries.