Adaptive Zincophilic-Hydrophobic Interfaces via Additive Engineering for Robust Zinc-Based Flow Batteries

Zinc-based flow batteries (Zn-FBs) have emerged as promising candidates for large-scale energy storage (ES) systems due to their inherent safety and high energy density. However, dendrite formation and water-induced parasitic reactions at the Zn anode critically compromise long-term operational stability. While aqueous Zn battery additives have been extensively explored, systematic selection criteria for high-areal-capacity Zn-FBs remain absent. Here, we establish zincophilicity and interfacial hydrophobicity as dual descriptors for additive screening. A dimensionless parameter η, defined as the ratio of the adsorption energy on Zn to the binding energy of free water molecules, identifies 1-ethylpyridinium bromide (EPD) as the most optimal pyridinium additive with the highest η value. Mechanistic studies reveal that EPD spontaneously assembles into a dynamic electric-field-responsive interface, which self-adapts to morphological perturbations during electrodeposition and guides Zn2+ flux along equipotential contours, preventing surface roughening. The in situ formed zincophilic-hydrophobic interphase alters interfacial chemistry by displacing reactive water molecules, achieving dual suppression of hydrogen evolution and dendrite propagation. Implementation of this strategy in Zn–Br2 flow batteries enables ultrastable cycling over 4000 cycles (166 days) at 40 mA cm–2, delivering a cumulative plating capacity of 80 Ah cm–2─about 11.4-fold improvement over the baseline system (7.0 Ah cm–2). This work demonstrates an adaptive interface engineering strategy that directs ion redistribution, advancing the development of reliable electrolytes for sustainable metal-based flow batteries.