Reconstructing Zn²⁺ Storage Pathways Enables Ultrastable High-Rate Zn-Air Flow Batteries

Despite their high theoretical energy density (1086 Wh kg^-1) and environmental compatibility, aqueous Zn-air flow batteries suffer from critical performance limitations at high current densities, including intensified concentration polarization, uncontrolled Zn dendrite growth, and hydrogen evolution reaction (HER) and corrosion, primarily driven by active water molecules and inadequate Zn²⁺ regulation in conventional electrolytes. Here we report a Bayesian optimization-guided electrolyte design employing alginic acid (AA) as a bifunctional additive to regulate both interfacial and bulk electrolyte chemistry. Under alkaline conditions, AA molecules coordinate with Zn²⁺ and further dynamically self-assemble, constructing reversible alginate-Zn²⁺ colloidal reservoirs instead of irreversible ZnO accumulation. Meanwhile, AA preferentially adsorbs on the Zn surface, modulating local ion flux and nucleation behavior to promote uniform Zn stripping/plating and mitigate dendrite growth, corrosion, and hydrogen evolution. This strategy achieves 2400 h of stable cycling at 20 mA cm^-2, significantly outperforming conventional systems. More broadly, this work demonstrates how data-driven electrolyte optimization combined with bio-derived polymer additives can reshape Zn²⁺ storage chemistry and mitigate the intrinsic current density-stability trade-off in Zn-air batteries.