Gradient‐Engineered Ultra‐Thin Lithium Metal Anodes with a Li–Si–N Alloy‐Based Lithiophilic Current Collector Interphase

Li metal anodes, with high theoretical capacity (3860 mAh g −1 ) and low redox potential, are promising for high‐capacity rechargeable batteries. Especially, ultra‐thin Li metal anodes can improve energy density and minimize lithium excess. However, their poor processability leads to non‐uniform Li layers and unstable plating/stripping behavior. In this study, we present a current collector interphase (CCI)‐based strategy using a Cu foil coated with a lithiophilic Si 3 N 4 layer, followed by molten Li dip‐coating to form around 20 μm Li layer. Furthermore, the scalable dip‐coating method, compatibility with large‐area current collectors (up to 100 cm 2 ), and stable cycling in pouch cells demonstrate the practical viability of the proposed SNLMA design for commercial lithium metal batteries. During the process, an in‐situ Li–Si–N alloy gradient interphase forms at the interface, enhancing wettability and mechanical integrity. This unique gradient CCI provides synergistic lithiophilicity and structural stability, enabling high‐performance Li metal batteries. The resulting Li x Si y and Li x N y phases reduce nucleation barriers and enable uniform Li deposition. As a result, the Si 3 N 4 –Li anode paired with a high‐loading LCO cathode (22 mg cm −2 ) achieved 83% capacity retention after 100 cycles. This work offers a scalable and practical CCI design for next‐generation Li metal batteries.