Assembly of Metal-Organic Chemical Conversion Layers as Ion Sieves along with Exposing Zn(002) Planes for Stable Zn Metal Anode

The development of aqueous rechargeable Zn metal batteries, as one of the most promising large-scale energy storage technology, is hindered largely by dendrite growth and surface passivation of Zn metal anode, which are deleterious to the battery life and Coulombic efficiency (CE). This report demonstrates that ethylenediamine tetramethylenephosphonic acid can in situ coordinate with Zn (EDTMP-Zn) along with exposing (002) planes for highly reversible and stable Zn plating/stripping. The zincophilic EDTMP-Zn layer may serve as ion sieves that homogenize Zn ion flux at the Zn anode surface and consequently induce uniform deposition of Zn. The hydrophobic groups in such functional layer is thought to circumvent the Zn anode surface from corrosion and hydrogen evolution reaction. EDTMP15-Zn modified Zn anode (EDTMP15-Zn@Zn) delivers a lifespan exceeding 1400 h at 5 mA cm-2, and 1 mAh cm-2 for Zn||Zn symmetric cell and improved CE of 99.7% over 1000 cycles in a Zn||Cu cell. The full cell coupled with NH4V4O10 cathode demonstrates improved rate performance and cycle stability. The zincophilic and hydrophobic ethylenediamine tetramethylenephosphonic acid-Zn complex layer is constructed on Zn anode surface to regulate ion flux and prevent active water from contacting with Zn, thereby inhibiting the dendrites growth and suppressing the side reactions. More exposed (002) planes during complexation also contribute to reversible and stable Zn deposition.image