Modulation of water reactivity by ethyl acetate/water co-solvent for zinc-metal batteries

Abstract

The realization of durable aqueous zinc-metal batteries is hindered by uncontrollable Zn dendrite growth and serious parasitic reactions. Here, a miscible ethyl acetate (EA)/H2O co-solvent electrolyte is constructed by salting-in effect of Zn(OTf)2 to manipulate the solvation structures of Zn2+ and disrupt the original strong H-bond networks built by H2O. It reveals that EA molecules and OTf- jointly forms EA-H2O-OTf- co-dominated solvation sheath structure, weakening the coordination between Zn2+ and water molecules, meanwhile promoting Zn2+ immigration in reconstructed co-solvent H-bond environment. Besides, de-solvation water molecules with higher ionization barrier significantly inhibits H2O reactivity. Further, the introduced EA molecules are prone to preferentially adsorbed in Holmhertz Electrical Double Layers, which forms a hydrophobic interphase to regulate the uniform distribution of Zn2+ fluxes by steric structure. Therefore, it realizes dendrite-free zinc deposition with long plating/stripping stability of over 1300 h at 1 mA cm−2. In particular, the low temperature (600 cycles at −40 ℃) and ultra-long durable (20,000 cycles with 100 % capacity retention) electrochemical performance in Zn||Active Carbon zinc-ion capacitors, as well as long cycling stability (average coulombic efficiency of 99.91 % at 1 A g−1 after 1000 cycles) in Zn|| NaV3O8·1.5H2O batteries are also achieved.