Sustained Release of Underpotential Deposition Initiators for Ah‐Level Zinc Metal Batteries

Electrolyte additives effectively stabilize aqueous zinc‐ion batteries (AZIBs), yet their depletion during long‐term cycling leads to eventual battery failure. Here, we address this common issue through sustained release of underpotential deposition initiators from an artificial solid electrolyte interphase (SEI) to achieve the long‐term operation. This SEI, comprising nickel hydroxide and nickel‐2‐methylimidazole complexes embedded in a hydrophobic dodecylphosphonic acid (DPA) monolayer via ion‐layer epitaxy, releases Ni2+ ions on‐demand when local pH rises due to corrosion. In this way, the protection through sustained and controlled release of underpotential deposition initiator over long‐term operation is achieved. Concurrently, the hydrophobic DPA layer restricts direct water contact, effectively suppressing side reactions. Consequently, the engineered Ni@DPA‐coated Zn electrode demonstrates remarkable stability, enduring over 37 500 cycles at 50 mA cm−2. Zn–I2 full cells retain exceptional cycling performance for over 30 000 cycles at 45 mA cm−2, achieving an unprecedented energy density of 270 Wh kg−1. An Ah‐level pouch cell (1.5 Ah) delivers a high areal capacity (13.8 mAh cm−2), maintaining 83% capacity after 400 cycles. Demonstrating practical application, a Zn–I2 pouch cell can be directly charged by an external solar panel with photovoltaic conversion efficiencies up to 10.8%. This approach significantly advances AZIBs toward practical, high‐performance energy storage.