Iminodiacetate Chelated Zinc Complex Electrolyte Enables High-Voltage and Long-Life Zinc-Based Flow Batteries

Conventionally, lowering the Zn plating/stripping potential relies on strongly alkaline electrolytes that convert Zn²⁺ into zincate species. However, such conditions often exacerbate Zn corrosion and severe dendrite growth. Here, we introduce an iminodiacetate (IDA^2-)-based coordination strategy that enables reversible Zn plating/stripping under mildly alkaline conditions (pH ∼12). The hexacoordinated [Zn(IDA)₂]^2- shifts the Zn plating/stripping potential to -1.17 V versus SHE. A demonstrated zinc-iodine flow battery delivers a voltage of ∼1.7 V with a peak power density of 561.5 mW cm^-2 and sustains cycling over 700 cycles at 100 mA cm^-2 with Zn areal capacity of 90 mAh cm^-2. This strategy is further validated in a zinc-iron redox flow battery, achieving an operating voltage of ∼1.6 V with average Coulombic efficiency of 99.3% over 750 cycles. Collectively, these results suggest that the proposed coordination chemistry offers a promising avenue toward the development of high-voltage long-life zinc-based redox flow batteries.