Synchronized regulating Zn2+ depositing/stripping processes to achieve ultra-stable aqueous zinc metal batteries

Abstract

The dendrites and parasitic reactions of zinc anodes constitute the critical bottleneck limiting the stable cycling of aqueous zinc-ion batteries. Regulating the depositing process of zinc ions and regulating the stripping process of zinc ions are both important to circumvent these parasitic reactions and zinc dendrites. However, there is still a lack of simple strategies that can effectively regulate the deposition and stripping behaviors of zinc ions on two opposite electrodes simultaneously. To address this challenge, we engineer copper disodium ethylenediaminetetraacetate (EDTA-CuNa₂) as a multifunctional electrolyte additive to efficiently and synchronously regulate both Zn²⁺ depositing and stripping processes. On the deposition side, Cu²⁺ maintains persistent exposure of zincophilic alloy sites, reducing the overpotential of zinc nucleation, while Na⁺ suppresses the growth of zinc dendrites via electrostatic shielding effects. On the stripping side, the interfacial molecular layer arranged by adsorbed EDTA^4- ligands facilitates uniform zinc stripping and prevents the proximity of sulfate ions to the electrode, which evades the formation of electrode surface defects caused by disordered Zn²⁺ stripping as well as the generation and aggregation of alkali by-products, thus maintaining the flatness of the stripping surface. The synergistic effect of the two aforementioned functions results in excellent cycling stability: Zn||Zn symmetric batteries manifest the stable cycling over 2500 h at 30 mA cm^-2/1 mAh cm^-2, and Zn||Cu half-batteries maintain >3700 cycles at 1 mA cm^-1/0.5 mAh cm^-2. This research delivers an exemplification for electrolyte additive-enabled uniform zinc deposition and stripping, carving out a novel pathway for realizing highly stable zinc-metal batteries.