In Situ Protective Interface Construction via a Cyano‐Ether Additive for Durable Zinc Metal Anodes

Aqueous zinc‐ion batteries (AZIBs) are promising for energy storage but are hindered by Zn anode instability, including dendrites, hydrogen evolution, and corrosion. We introduce 1,2,3‐tris(2‐cyanoethoxy)propane (TCEP), a multi‐cyano molecule with flexible ether chains, as an additive. Theoretical and experimental results show TCEP preferentially adsorbs on Zn due to higher HOMO and lower LUMO levels than H 2 O, enabling in situ formation of a robust organic–inorganic hybrid SEI that regulates Zn 2+ deposition, suppresses dendrites, and mitigates side reactions. Thus, Zn//Zn symmetric cells achieve >4900 h cycling at 2 mA cm −2 and 1 mAh cm −2 , and >300 h at 68.4% depth of discharge. Zn//Cu half‐cells deliver 99.6% average Coulombic efficiency after 1300 cycles. Moreover, Zn//MnO 2 full cells retain 141.56 mAh g −1 after 700 cycles, and Zn//NH 4 V 4 O 10 pouch cells retain 86.9% capacity after 680 cycles. This work demonstrates that rational cyano‐based additive design offers a promising interface strategy for high‐stability, practical aqueous zinc batteries.