A multifunctional phenylalanine additive stabilizing zinc anodes in aqueous zinc ion batteries

Abstract

Aqueous Zn-based batteries, promising energy storage devices for grid-scale applications, are restricted by the limited reversibility of Zn anodes. This work explores the use of the aromatic amino acid phenylalanine (Phe) as a multifunctional additive in an aqueous electrolyte to enhance Zn anode stability. The electron-rich groups within the structure of Phe interact strongly with Zn²⁺ cations in the electrolyte, regulating the solvation sheath of Zn²⁺. These groups facilitate preferential adsorption of Phe molecules at the electrode–electrolyte interface, reshaping the inner Helmholtz plane and reducing water adsorption. The amphoteric nature of Phe, with the pH-buffering effect, enhances the anti-corrosion ability of zinc anodes, suppressing by-product formation. By adjusting the Zn plating/stripping kinetics, Zn/Zn symmetric cells achieve an extended cycle life of 2000 hours with an optimal concentration of 10 mM Phe. It is found that the efficacy of additives in improving zinc anode reversibility strongly relies on their interfacial engineering behavior. An optimal coulombic efficiency of 99.24% is achieved in Cu/Zn cells with 5 mM of Phe in the electrolyte. With good compatibility with the cathode material, zinc hexacyanoferrate/Zn full batteries using Phe electrolyte additives deliver ameliorated electrochemical performance. The results highlight Phe as a promising electrolyte additive for optimizing the stability of aqueous Zn-based batteries.