Dynamic pH Regulation and Interfacial Ion Redistribution via Molecular Buffering for Dendrite-Free Zn Metal Anodes

Aqueous Zn ion batteries suffer from irreversible anode degradation caused by hydrogen evolution reaction (HER)-driven electrolyte alkalization and non-uniform Zn deposition. Here, a bi-functional buffer additive is proposed that synergistically couples pH regulation and interfacial ion-redistribution. The buffer additive maintains electrolyte with a self-regulated pH (≈3) through proton donor-acceptor equilibria, effectively scavenging hydroxyl ions to prevent Zn passivation, while inducing preferential Na⁺ adsorption at protrusions to enforce planar Zn deposition via charge screening effects. This dual mechanism enables an ultralow nucleation overpotential (24.5 mV) and an ultrahigh Coulombic efficiency (99.9% over 12 000 cycles) in Cu–Zn half cells. Full cells with NaV₃O₈ cathodes achieve 93% capacity retention after 3000 cycles at 10 A g⁻¹, while pouch cells (20.89 mg cm⁻² cathode) retain 81.6% capacity over 300 cycles at 1 A g⁻¹. This work establishes a universal paradigm for stabilizing Zn anodes through coupled thermodynamic and kinetic regulation, positioning Zn-ion batteries as viable candidates for grid-scale energy storage.