Dynamic Proton Activity Regulation via Brønsted Bases Enables Durable and High-Energy-Density Zn||MnO₂ Batteries

Acidic Zn||MnO₂ batteries offer exceptional promise for grid-scale storage due to high theoretical energy and power densities, yet their practical deployment is fundamentally limited by conflicting proton activity requirements at the electrodes: the MnO₂ cathode demands high H⁺ concentration to drive reversible two-electron Mn²⁺/MnO₂ conversion, while the Zn anode suffers severe hydrogen evolution corrosion (HEC) under these conditions. We resolve this incompatibility by designing a dynamically regulated weak-acid electrolyte using strategically introduced Brønsted bases. The tuned proton affinity kinetically suppresses acid dissociation at the Zn/electrolyte interface to mitigate HEC, while sustaining high-voltage Mn²⁺/MnO₂ conversion at the MnO₂ cathode. This intrinsic kinetic regulation achieved without electrolyte decoupling, protective interphases, or uncontrolled pH drift enables designed Zn||MnO₂ cells to achieve an ultrahigh energy density of 951 Wh kg⁻¹ (based on MnO₂ cathode mass) and exceptional cycling stability (80% capacity retention after 200 cycles at 0.5 A g⁻¹). This work establishes a practical, scalable electrolyte platform for durable high-performance Zn||MnO₂ batteries. © 2026 The Author(s).