Trace-Level Green Bio-Derived Amino Acid Molecular Leveling Agent Enables Dendrite-Free and Long-Lifespan Zinc Metal Anodes.

Abstract

The poor reversibility of Zn metal anodes, caused by dendrite growth and water-induced side reactions, hinders the commercialization of aqueous zinc-ion batteries (AZIBs). To address these issues, regulating Zn²⁺ solvation structure, controlling nucleation behavior, and constructing a robust solid electrolyte interphase (SEI) are crucial. Herein, a trace-level (10 mg mL^-1) bio-derived surface-leveling agent, N,N-dihydroxyethyl glycine (BICINE), is introduced to tailor the interfacial environment. With multiple coordinating groups, BICINE adsorbs onto the Zn surface, homogenizes nucleation, reconstructs solvation sheath, and induces a hybrid SEI. Meanwhile, it promotes the formation of a uniform cathode electrolyte interphase (CEI), stabilizing cathode morphology and preventing irreversible degradation. These synergistic effects suppress dendrite growth and parasitic reactions, enabling highly reversible Zn plating/stripping. Consequently, symmetric Zn||Zn cells demonstrate remarkable stability, with the capability to operate for over 5,300 h at 5 mA cm^-2/1 mA h cm^-2 and maintain stable performance at a high depth of discharge (88.2%). Asymmetric Cu||Zn cells exhibit exceptional Coulombic efficiency of 99.9% over 1,650 cycles. Even with a low N/P ratio of 3, Zn||NH₄V₄O₁₀ full cells retain 89.7% of their capacity after 250 cycles at 2 A g^-1. The low-cost BICINE strategy holds great promise for advancing the commercialization of AZIBs.