Molecule Isolation Protective Interface Formed by Planar Additive for Stable Sodium Metal Anodes

Sodium (Na) metal is an ideal anode for Na-based batteries because of its high specific capacity and low potential. However, interface issues such as side reactions with the electrolyte and uneven deposition severely hinder its practical application. Here, we report a zinc phthalocyanine (ZnPc) electrolyte additive with a planar molecular structure that can form a dense molecular layer when tightly adsorbed on the Na metal anode surface. Such a planar molecular layer can suppress side reactions between the anode and the electrolyte as well as homogenize Na + flux to reduce dendrite growth. As a result, the molecular isolation interface formed by ZnPc adsorption on the surface of the Na metal anode enhances the interface stability and the cycling performance of the Na metal anode, with the average Coulombic efficiency of the half-cell of 99.95% after 350 stable cycles at 1 mA cm –2 for 1 mAh cm –2 . Moreover, the assembled Na||Na 3 V 2 (PO 4 ) 3 full-cell with this additive delivers excellent stability over 120 cycles, proving the effectiveness of the ZnPc additive in practical application.