Selective Masking of Active Sites in Zinc Metal via Galvanic Replacement Reaction for Highly Reversible Ah-Level Zinc-I₂ Batteries

Zinc metal anodes suffer from severe dendrite formation and corrosion due to active Zn sites. Here, an ultrathin, hydrophobic copper phosphate (CP) membrane is introduced that selectively masks active Zn sites with electrochemically inactive copper through a galvanic replacement reaction (Zn⁰ + Cu²⁺ = Cu⁰ + Zn²⁺). Copper is deliberately chosen for its higher redox potential (Cu²⁺/Cu⁰; +0.34 V vs SHE), which effectively inhibits both the corrosion reaction (H⁺/H₂; 0 V vs SHE) and dendrite formation (Zn²⁺/Zn⁰; −0.76 V vs SHE). In this way, the CP layer masks protrusions and grain boundaries on the zinc anode surface with inactive copper, blocking corrosion and dendritic growth, while its hydrophobic top layer reduces water activity at the interface. Benefiting from the deactivated anode surface, the resulting CP/Zn anode demonstrates exceptional stability, sustaining over 11,000 plating/stripping cycles at 10 mA cm⁻² with an average Coulombic efficiency of 99.98 %. Moreover, a CP/Zn||I₂ full cell with an N/P ratio of 1.85 achieves an energy density of 187 Wh kg⁻¹_electrodes, while a 1.2-Ah pouch cell validates its practical feasibility. This work highlights the importance of designing suitable surface chemistry to protect the Zn metal anode and indicates promising applications in other metal anodes.