Zincophilic Natural Organic Electrolyte Additives Enable Highly Reversible Zinc Metal Anodes

Disordered dendritic growth and numerous side reactions have long plagued researchers, severely reducing the cycling stability of aqueous zinc-ion batteries (AZIBs) and posing a key barrier to commercialization. To address this, l-theanine was used in this work as a natural and effective electrolyte additive. Its zincophilic groups adsorb on the zinc anode, guiding Zn²⁺ to deposit uniformly along the (002) crystal plane and effectively suppressing side reactions like hydrogen evolution reaction and corrosion, thereby significantly enhancing battery cycling stability. Results show that with l-theanine as an electrolyte additive, Zn//Zn symmetric cell stably cycled for 1093 h at 5 mA cm^-2 and 5 mA h cm^-2, about 14.4 times longer than that without the additive. Zn//Cu half-cell also retained an average Coulombic efficiency of 97.6% over 267 cycles. Furthermore, Zn//V₂O₅ full cells demonstrate remarkable cycling stability over 4000 cycles at 2 A g^-1 and maintain excellent capacity retention across a wide temperature range from 20 to 60 °C. These findings offer a feasible and effective strategy for developing electrolyte additives for AZIBs.