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.