<p>Aqueous Zn²⁺/Zn||MnO₂/Mn²⁺ batteries—operating via electrodeposition/dissolution—offer promising high-voltage, high-capacity grid-storage capabilities but require acidic conditions for MnO₂/Mn²⁺ conversion, and these induce problematic zinc corrosion. Here we present a global approach that identifies deep eutectic aqueous–organic electrolytes that strategically disrupt water’s hydrogen-bonding network, simultaneously enhancing MnO₂ reversibility at the cathode while enabling stable zinc cycling at the anode without water decomposition. Such non-flammable electrolytes regulate the cation solvation structure and phase of the deposited MnO₂ and its morphology, promoting layered structures with enhanced ion-transport pathways that significantly improve stripping efficiency. These deep eutectics increase the oxygen evolution overpotential well above the MnO₂ deposition potential, which completely suppresses unwanted O₂ evolution. Moreover, they alter the local environment at the cathode interface to create localized interfacial pH gradients that influence critical processes, including optimizing proton transport and MnO₂ stripping. Our Zn²⁺/Zn||MnO₂/Mn²⁺ dual-electrode-free battery achieves high Coulombic efficiency for extended cycling (&gt;5,000 cycles) without external acid addition, advancing high-energy-density zinc–manganese battery development through rational electrolyte design.</p>