Stabilizing Zinc Electrodes with a Vanillin Additive in Mild Aqueous Electrolytes

Metallic zinc (Zn) is an attractive anode material to use for building an aqueous battery but suffers from dendritic growth and water-induced corrosion. Herein, we report the use of vanillin as a bifunctional additive in aqueous electrolyte to stabilize the Zn electrochemistry. Computational, spectroscopic, and electrochemical studies suggest that vanillin molecules preferentially absorb in parallel on the Zn surface to homogenize the Zn²⁺ plating and favorably coordinate with Zn²⁺ to weaken the solvation interaction between H₂O and Zn²⁺, resulting in a compact, dendrite-free Zn deposition and a stable electrode-electrolyte interface with suppressed hydrogen evolution and hydroxide sulfate formation. In the formulated 2 M ZnSO₄ electrolyte with 5 mM vanillin, the Zn anode sustains high areal capacity (10 mAh cm^-2 at 1 mA cm^-2) and remarkable cycling stability (1 mAh cm^-2 for 1000 h) in a Zn|Zn cell and high average Coulombic efficiency (99.8%) in a Zn|Cu cell, significantly outperforming the cells without vanillin. Furthermore, the vanillin additive supports stable operation of full Zn|V₂O₅ batteries and is readily generalized to a Zn(CF₃SO₃)₂-based electrolyte. This work offers a facile and cost-effective strategy of electrolyte design to enable high-performance aqueous Zn batteries.