Stabilizing Zn metal anode by interfacial self-assembled zincophilic metal-organic complex conversion layers

The reversibility and stability of aqueous Zn metal batteries is largely constrained by the wild Zn dendrites growth and sever side reactions. A stable electrode/electrolyte interface is a necessity for Zn anodes. In the present work, a metal-organic complex conversion layer (CCL) is in situ constructed on the Zn anode surface via the complexation effect through adding 30 mg L- 1 2-Hydroxyphosphonoacetic acid (HPAA) in 2 M ZnSO4 4 electrolyte (ZnSO4+30 4 +30 mg L- 1 HPAA). Calculations and experiments reveal that a zincophilic HPAA-Zn layer is formed on the Zn anode surface by chemical adsorption of HPAA with P-OH group, which is in favor of providing even diffusion and distribution of zinc ions to promote uniform Zn deposition. The HPAA with abundant functional groups could also disrupt the hydrogen bond and reduce water activity to suppress the water-related side reactions. As a result, Zn||Zn symmetric cell using ZnSO4+30 4 +30 mg L- 1 HPAA electrolyte displays a stable Zn plating/stripping for 1200 h at 10 mA cm-- 2 and 1 mAh cm-- 2 . A high average Coulombic efficiency of 99.8 % over 1000 cycles is achieved in corresponding Zn||Cu asymmetric cell. The Zn||NH4V4O10 4 V 4 O 10 full cell-based optimal electrolyte delivers a superior rate capability as well as an improved cycling stability over 1000 cycles.