LiNO ₂ Additive Enables Faster Formation of Li ₃ N‐Rich Interphase with High Ionic Conductivity for Cycling Stable Lithium Metal Battery

ABSTRACT Lithium metal anodes (LMAs) are ideal for next‐generation high‐energy‐density batteries, owing to their low redox potential and high theoretical capacity. However, the formation of unstable solid electrolyte interphases (SEIs) induces severe interfacial instability, which fundamentally limits practical implementation. Lithium nitride (Li 3 N) has emerged as an SEI critical component due to its exceptional ionic conductivity and mechanical robustness, yet achieving high Li 3 N content in SEI remains challenging, as conventional additives (e.g., LiNO 3 ) predominantly yield low‐conductivity Li 2 O during decomposition, severely limiting Li 3 N enrichment. To address this, we develop LiNO 2 as a novel electrolyte additive. Possessing higher nitrogen content than LiNO 3 , LiNO 2 can preferentially decompose faster and preferentially to form a Li 3 N‐rich SEI film, thereby enhancing interfacial ion transport and significantly improving battery performance. Electrochemical testing demonstrates: LiNO 2 ‐modified Li||Li symmetric cells achieve >700 h stable plating/stripping; Li||Cu cells exhibit a high Li plating/stripping Coulombic efficiency of 98.52%; Li||NCM811 full cells retain >88% capacity after 200 cycles, outperforming conventional carbonate and LiNO 3 ‐containing electrolytes. This work elucidates the advantages of LiNO 2 as a newly developed electrolyte additive for constructing a rich Li 3 N SEI for high‐performance lithium metal batteries.