Self-Assembled Monolayer Enables a Nucleophilic Interfacial Layer for Highly Reversible Zinc Metal Anode

Aqueous zinc-ion batteries (AZIBs) are promising candidates for next-generation energy storage systems. However, the practical implementation is hindered by challenges associated with zinc (Zn) dendrite growth and parasitic side reactions. Here, we designed a self-assembled monolayer (SAM) using theanine (CA) to modify the Zn anode. As expected, CA can strongly interact with the Zn substrate through the carboxyl groups, forming a compact and uniform SAM. The amino and amide functional groups of CA exhibit high Zn affinity, effectively regulating Zn²⁺ flux and achieving uniform Zn deposition. The ultrathin interface provided by the CA monolayer acts as a barrier to water molecules, thereby suppressing hydrogen evolution reactions (HER) and minimizing the formation of undesirable byproducts. As a result, Zn anodes protected by a CA monolayer demonstrate exceptional durability, operating for over 2000 h at a current density of 5 mA cm^-2 and an areal capacity of 2 mAh cm^-2. Additionally, full cells paired with NH₄V₄O₁₀ cathodes also demonstrate superior reaction reversibility and high capacity retention. The CA-based SAM holds promise for overcoming critical challenges faced in Zn anode and advancing the development of stable and efficient AZIBs.