Multi-dentate organic additives for simultaneous Zn2+ capturing and interfacial engineering toward stable aqueous zinc metal batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have recently attracted widespread interest due to their intrinsically high specific capacity and inherent safety. Nevertheless, the application of aqueous electrolytes introduces significant challenges, including zinc dendrite growth, side reactions, and fragile solid electrolyte interphase (SEI) layers. To overcome these challenges, this study proposes a novel multi-dentate electrolyte additive, 2,2′-bipyridine-6,6′-dicarboxylic acid, which features multiple coordination sites, including two carboxyl groups and two pyridinic nitrogen atoms. The multifunctional sites can significantly enhance the coordination effects with Zn²⁺ ions, while carboxyl ends can robustly anchor onto the zinc anode surface, and effectively stabilize the SEI layer during the electrochemical process. The electrochemical results indicate that symmetric cells incorporating this additive exhibit remarkably stable overpotentials during cycling and maintain stable galvanostatic plating/stripping performance for over 550 h at a high areal capacity of 5 mAh cm⁻² and a current density of 5 mA cm⁻². Furthermore, full cells employing the additive demonstrate stable cycling performance for over 1000 cycles with an outstanding coulombic efficiency of 99.89%. Accordingly, the incorporation of this electrolyte additive is expected to enable the advancement of AZIBs with enhanced stability and electrochemical performance.