Scalable Cr(III) Passivation Engineering for Effectively Suppressing Zinc Escape Toward Practical Ah‐Level Aqueous Zinc‐Ion Batteries

The self‐corrosion of zinc anodes, caused by zinc atom escape and hydrogen evolution, remains a fundamental obstacle to the deployment of aqueous zinc‐ion batteries (AZIBs) in sustainable energy storage systems. Herein, we develop a scalable Cr(III) passivation strategy that constructs an ultrathin (∼100 nm), dense Cr 2 O 3 layer on the zinc surface, delivering the highest zinc chemical potential (6.96 eV) among various commercial passivation materials. This design establishes a steep chemical potential gradient, significantly elevating the energy barrier for zinc escape and thereby mitigating self‐corrosion under resting conditions. Moreover, strong electrostatic interactions between Cr 2 O 3 and [Zn(H 2 O) 6 ] 2+ accelerate Zn 2+ desolvation and migration, guiding zinc to deposit beneath the passivation layer while eliminating interference from solvated water molecules. Benefiting from its ability to inhibit static corrosion and stabilize the electrode interface during cycling, the electrode achieves remarkably stable operation over 7300 h. Furthermore, full‐cell integration with commercial MnO 2 shows negligible capacity fading over 200 cycles in a 1 Ah hard‐shell battery, and an unprecedented device energy density of 45 Wh kg −1 is achieved at an ultrahigh capacity up to ∼4 Ah. This work establishes an effective interfacial design that alleviates resting‐state corrosion and enhances cycling stability for promoting the practical application of AZIBs.