A Self‐Regulated Interface Enabled by Multi‐Functional pH Buffer for Reversible Zn Electrochemistry

Abstract Aqueous Zn‐ion batteries with mild acidic electrolytes are considered the promising energy storage solutions due to their outstanding merits of high energy density and cost‐effectiveness. However, the rampant dendrite growth and severe parasitic reactions caused by a series of factors such as irregular Zn 2+ transport pathway and pH variation would result in poor cycling stability. Herein, a self‐regulated interface strategy implemented by ammonium persulfate ((NH 4 ) 2 S 2 O 8 , denoted as APS) multifunctional additive is proposed to simultaneously address the above issues. The zincophilic NH 4 + preferentially adsorbs on the Zn protuberance to exclude water molecules and shield the “tip effect,” thus inhibiting side‐reactions and inducing uniform Zn deposition. Moreover, NH 4 + and S 2 O 8 2− can dynamically adjust H + and OH − concentrations in a pH self‐buffer manner, thus effectively mitigating hydrogen evolution reaction and formation of by‐products. Consequently, with the existence of APS additive, Zn anode exhibits ultrahigh coulombic efficiency (CE) of 99.9% over 9000 cycles and ultra‐long lifespan of 4300 h at 5 mA cm −2 . Furthermore, even under high NH 4 V 4 O 10 mass loading (9.4 mg cm −2 ) and thin zinc foil (10 µm), the assembled NH 4 V 4 O 10 //Zn pouch cell with APS additive can still maintain stably over 210 cycles, demonstrating its excellent value for application.