An Amphoteric Molecule Electrolyte Additive for Highly Stable Zinc Metal Anode

Abstract Aqueous zinc-ion batteries (AZIBs) possess inherent safety and cost-effectiveness, rendering them highly attractive for energy storage applications. However, their development is critically constrained by water-triggered parasitic reactions, namely, the inactive by-products and the hydrogen evolution reaction (HER). Herein, we propose tranexamic acid (TA) as an amphoteric electrolyte additive to mitigate the parasitic reactions. Theoretical and experimental analyses collectively demonstrate that TA molecules not only restructure the water–water hydrogen bond network but also actively integrate into the primary coordination shell of Zn2+, which effectively suppresses HER kinetics and promotes the uniform Zn deposition. Concurrently, the amphoteric nature of TA molecules serves as a pH buffer, which further inhibits the HER and prevents the precipitation of inactive by-products. As a result, the Zn–Zn symmetric cell delivers a prolonged cycle life over 4000 h (1 mA cm–2, 1 mAh cm–2) and 146 h at a high 80% Zn utilization rate (areal capacity of 40 mAh cm–2). Meanwhile, the TA additive enables reversible Zn plating and stripping for 1500 cycles with an average Coulombic efficiency of 99.7%. The assembled Zn–VO2 full cell further reveals robust capacity retention in a negative to positive capacity ratio of 1.5 after 200 cycles. This work elucidates a multifunctional electrolyte engineering approach toward next-generation AZIBs.