Toward long-life Zn anode using highly polar electrolyte additives

Abstract

Unstable Zn interface caused by rampant dendrite growth and parasitic side reactions always hinders the practical application of aqueous zinc metal batteries (AZMBs). Herein, tyrosine (Tyr) with high molecular polarity was introduced into aqueous electrolyte to modulate the interfacial electrochemistry of Zn anode. In AZMBs, the positively charged side of Tyr can be well adsorbed on the surface of Zn anode to form a water-poor layer, and the exposed carboxylate side can be easily coordinated with Zn²⁺, favoring inducing uniform plating of Zn²⁺ and inhibiting the occurrence of water-induced side reactions. These in turn enable the achievement of highly stable Zn anode. Accordingly, the Zn anodes achieve outstanding cyclic stability (3000 h at 2 mA cm⁻², 2 mA h cm⁻² and 1300 h at 5 mA cm⁻², 5 mA h cm⁻²), high average Coulombic efficiency (99.4% over 3200 cycles), and high depth of discharge (80% for 500 h). Besides, the assembled Zn||NaV₃O₈·1.5H₂O full cells deliver remarkable capacity retention and ultra-long lifetime (61.8% over 6650 cycles at 5 A g⁻¹) and enhanced rate capability (169 mA h g⁻¹ at 5 A g⁻¹). The work may promote the design and deep understanding of electrolyte additives with high molecular polarity for high-performance AZMBs.