Hydronium-catching interface unlocks strongly acidic Zn metal batteries with high voltage and long-term stability

Abstract

Strongly acidic aqueous batteries promise high voltage and fast kinetics but are fundamentally limited by the instability of metal negative electrodes such as Zn. Here, we demonstrate reversible Zn plating/stripping at pH = 0 by regulating the hydronium accessibility at the electrode–electrolyte interface. A defect-engineered MOF-801 coating creates a confined interfacial microenvironment, where the hydrophobic pore entrances can exclude bulk water and the defect-derived –COOH/–OH groups selectively trap hydronium. This regulation reorganizes the inner Helmholtz layer into a hydronium-depleted configuration, inducing the partial Zn²⁺ desolvation, suppressing hydrogen evolution, and homogenizing the Zn²⁺ flux. Consequently, the MOF-protected Zn symmetric cells can achieve stable cycling for longer than 1660 h at 1 mA cm⁻² in the pH 0 electrolyte. The strategy further enables record performance in Zn–PbO₂ (2.35 V), Zn–MnO₂ (502.8 Wh kg⁻¹), and Zn-ion hybrid capacitors (30 000 cycles), extending the operational pH boundary of aqueous electrochemistry.