Strengthened Zinc Anode by Trace Natural Amino Acid β-Alanine in Aqueous Electrolyte Inspired by Synial Membrane: An Experimental Survey

Zinc corrosion, hydrogen evolution reaction, uneven deposition, and dendrite growth on the zinc anodes are the key factors restraining the electrochemical performance and cycling stability of the aqueous zinc-ion batteries. In this study, learned from the synial membrane, a tiny amount of natural amino acid β-alanine (β-Ala, 0.089 wt %) was introduced as the additive in ZnSO₄ electrolyte for strengthening the kinetics of the zinc anode as well as enhancing the performance of zinc ions batteries. A number of modern surface techniques and surface electrochemical analyses were employed to reveal the fundamental reasons for the strengthened zinc anode by β-Ala in ZnSO₄ electrolyte. The results show that β-Ala could be adsorbed on zinc electrode surface through intermolecular chelation, which might regulate the chemical environments of the electrolyte and promote uniform deposition of zinc ions. Hence, the β-Ala adsorption film on zinc electrode could suppress the hydrogen evolution reaction and the formation of zinc dendrites, thereby significantly improving the deposition/stripping process of the zinc anode. In particular, the strong hydrogen bonding could restrain the migration of H₂O molecules approaching the zinc anode surface, preventing the invasion of water to the zinc electrode surface. Therefore, the addition of dilute β-Ala in the ZnSO₄ electrolyte might remarkably prolong the life span of Zn||Zn symmetric batteries to 5000 h under 1 mA cm^-2 and 1 mAh cm^-2, and to 450 h under 5 mA cm^-2 and 3 mAh cm^-2 at 298 K, which is much longer than the zinc-zinc symmetric cells including the bare ZnSO₄ electrolyte (only 95 h at 5 mA cm^-2 and 3 mAh cm^-2, and 200 h at 1 mA cm^-2 and 1 mAh cm^-2). Furthermore, β-Ala was found to significantly improve the cycling stability of Zn||Cu asymmetric cells and Zn||V₂O₅ full cells. This study provides an effective method for engineering electrolytes to inspire rechargeable zinc-ion batteries by selecting ideal natural biomolecules as the electrolyte additives.