Fully dry-processed electrodes for highly reversible aqueous zinc powder-based batteries

Aqueous zinc-ion batteries have advanced rapidly, but practical deployment is limited by excessive negative-to-positive (N/P) ratios (>50), decreasing the energy density. Zinc powder anodes can lower N/P, yet their high specific surface area accelerates parasitic reactions and shortens lifespan. Here we report a high-loading and highly reversible dry-processed zinc powder anode with a non-electrochemically driven solid-electrolyte interphase (SEI). The dry process retains a homogeneous distribution of a sodium phosphate SEI precursor throughout the anodes, triggering spontaneous formation of a zinc phosphate-based SEI upon electrolyte contact that suppresses hydrogen evolution and zinc corrosion. Coupling this anode with dry-processed cathodes (90 mg cm^-2; 12.5 mAh cm^-2) yields the fully dry-processed aqueous zinc battery. A pouch cell delivers 88.8% capacity retention after 530 cycles at N/P ∼ 3, outperforming prior zinc powder systems despite ∼20-fold higher cathode loadings and providing a scalable path to high-energy-density aqueous zinc batteries for practical grid-scale storage.