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

Abstract 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, Zn 3 (PO 4 ) 3 ·4H 2 O (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 Zn 0 , 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 P 2 O 5 , Zn 0 , and Zn(OH) 2 . Meanwhile, the local reaction between P 2 O 5 and H 2 O reproduces H 3 PO 4 , which provides a condition to reproduce Zn 3 (PO 4 ) 2 ·4H 2 O via a reaction between H 3 PO 4 and metallic Zn on the Zn metal anode. This cyclic reformation of Zn 3 (PO 4 ) 2 ·4H 2 O progressively prevents dendrites over the long‐term, even at high rates. The compatibility is verified in NaV 3 O 8 ||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.