Amino acid-based complexing agents for improved Zn anode performance in near-neutral aqueous Zn-air batteries

Abstract

Aqueous electrolytes used in zinc-air batteries often face issues with low stability and unwanted side reactions, especially under alkaline conditions. This highlights the need for alternative electrolyte systems, such as nearneutral electrolytes. In this study, we explore the innovative use of amino-acid-based complexing agents, specifically glycine (Gly) and iminoacetic acid (IDA), to enhance the performance of Zn electrodes in a 2 M NaCl electrolyte. Unlike traditional additives, these amino acids serve a multi purpose: they coordinate with Zn2* ions in the bulk electrolyte and simultaneously regulate the interface between Zn and the electrolyte, while providing pH stability. Density functional theory (DFT) calculations indicate that this unique interaction alters the solvation shell of Zn2*, which helps reduce the formation of a passivation layer. In-operando X-ray computed tomography (XCT) further demonstrates that the amino-acid additives facilitate uniform Zn deposition and improve the cycling stability of the plating and stripping process. This work highlights the significance of solvation shell modulation in optimizing electrochemical performance and offers valuable insights for the development of near-neutral electrolyte-based Zn-air batteries.