Nature of Zinc‐Derived Dendrite and Its Suppression in Mildly Acidic Aqueous Zinc‐Ion Battery

Aqueous zinc‐ion batteries (ZIBs) are attractive in energy storage due to the use of aqueous electrolytes that ensures safety and ease of handling all parts in air. However, catastrophic zinc dendritic growth on zinc metal anodes impedes their practical application. Herein, Zn3(PO4)3·4H2O (ZP)‐coated zinc metal anode is introduced to effectively suppress the dendrite growth and the chemical state of the dendrites that are composed of metallic Zn0, ZnO, and Zn(OH)2 is elucidated first. Significant improvement is observed for the ZP‐coated zinc metal symmetric cell. Operando synchrotron tomography demonstrates that the ZP‐coating layer ensures uniform deposition of zinc‐derived compounds by the ZP layer that scarifies itself through decomposition to P2O5, Zn0, and Zn(OH)2. Meanwhile, the local reaction between P2O5 and H2O reproduces H3PO4, which provides a condition to reproduce Zn3(PO4)2·4H2O via a reaction between H3PO4 and metallic Zn on the Zn metal anode. This cyclic reformation of Zn3(PO4)2·4H2O progressively prevents dendrites over the long‐term, even at high rates. The compatibility is verified in NaV3O8||ZP‐coated zinc anode cell over 1000 cycles. As a result, this finding presents a practical way for uniform deposition of Zn that can be applicable to aqueous and nonaqueous ZIBs. A Zn3(PO4)2·4H2O coating layer on Zn metal anodes effectively suppresses severe dendritic growth during long‐term stripping/plating tests. The cyclic reformation of the Zn3(PO4)2·4H2O coating layer guarantees maintenance of the modified surface and greatly prolongs cycling in Zn||Zn symmetric cell test at a high current density of 20 mA cm−2 for 15 600 cycles.