A Bifunctional Electrolyte Additive for Durable Ah-Level Alkaline Zinc–Nickel Batteries

Alkaline zinc–nickel batteries (AZNBs) have attracted increasing research interest due to their high power density, wide operating temperature, and environmental friendliness. However, their practical application is significantly hindered by issues such as zinc dendrite growth and hydrogen evolution. In this study, the chelating agent tetrasodium ethylenediaminetetraacetate (Na4EDTA) is introduced into the electrolyte. Characterization techniques and density functional theory (DFT) calculations demonstrate that EDTA anions adsorb onto the anode surface and coordinate with Zn2+ anions during discharge. This interaction modulates the formation rate of Zn(OH)42–, suppresses anode passivation, and promotes uniform zinc deposition. Leveraging its octahedral chelating architecture composed of four oxygen and two nitrogen atoms, it forms a highly stable complex with Zn2+ that dynamically displaces water molecules in the electrolyte. Benefiting from the dual-control effects of Na4EDTA, the Zn symmetric battery with the modified electrolyte exhibits a significantly enhanced cycling performance. Furthermore, an Ah-level zinc–nickel battery assembled with the Na4EDTA-modified electrolyte maintains high capacities even after 200 cycles, whereas the control battery fails after about 20 cycles. These findings offer valuable insights for the development and practical application of alkaline zinc-based electrolytes in energy storage systems.