Simultaneous regulation on solvation shell and electrode interface for sustainable zinc-based flow batteries

The practical implementation of Zn-based flow batteries encounters the challenges associated with uneven deposition of Zn ions and undesirable side reactions. Here, a hybrid Zn-based electrolyte system composed of ZnBr₂, ethylene glycol (EG), H₂O and potassium gluconate (KGlu) is developed as anolyte to modulate the solvation structure and interface engineering for a sustainable Zn-based flow battery. The EG molecules could exclude water molecules outside the solvation structure, inhibiting the water-induced side reactions and Zn corrosion. Moreover, the incorporation of potassium gluconate constructs an artificial stable anionic interface for dendrite-free Zn deposition. Chemical stability and hydrogen evolution potential tests demonstrate that the activity of water molecules could be suppressed in the EG-containing hybrid electrolyte. Deposition morphologies and Zn//Zn symmetric flow battery tests also reveal that gluconate anions preferentially adsorbed on zinc anode could effectively facilitate uniform zinc deposition. As a result, the Zn-based flow battery with the proposed hybrid electrolyte delivers a stable cycling performance over 200 cycles and high reversibility with an average CE of over 97.4 % at 20 mA cm⁻², exhibiting a peak power density of 103.2 mW cm⁻². This work provides a universal electrolyte design strategy for realizing a sustainable Zn-based flow battery.