Multifunctional Amphoteric Additive Alanine Enables High‐Performance Wide‐pH Zn Metal Anodes

Interfacial pH fluctuation is one of the primary reasons for issues related to Zn metal anodes. Herein, polar amphoteric alanine, as a multifunctional electrolyte additive, is designed to regulate the electric double layer (EDL) and solvation structure. Alanine with self-adaptation capability to pH can stabilize electrolyte pH. Due to more negative adsorption energy, alanine preferentially adsorbs on the Zn surface and repels water molecules within the EDL. Alanine-enriched EDL effectively shields the surface tips, homogenizes interfacial electric field distribution, and promotes preferential deposition of horizontal flaky Zn. Alanine-enriched EDL limits the contact between water and the Zn anode. Alanine additive decreases the quantity of water molecules in the Zn²⁺ solvation sheath and disrupts H-bond networks in the electrolyte. Consequently, a dense and textured Zn deposition is achieved. Corrosion and side reactions are suppressed. Cycling stability of symmetrical cells attains 2700 h at 3 mA cm^-2/1 mAh cm^-2 and 2050 h at 5 mA cm^-2/1 mAh cm^-2. Average coulombic efficiency reaches 99.8% over 4500 cycles at 5 mA cm^-2/1 mAh cm^-2. Even within KOH alkaline electrolytes, alanine additive still improves the cycling lifespan of symmetrical cells to 100 h at 0.5 mA cm^-2/0.5 mAh cm^-2.