A preferentially adsorbed layer on the Zn surface manipulating ion distribution for stable Zn metal anodes

Although one of the most promising grid-scale energy storage systems, aqueous zinc metal batteries are plagued by water corrosion, interfacial side reactions and dendrite growth, which result in the increase of local pH and byproduct formation on the zinc anode, thus deteriorating the coulombic efficiency (CE) and cycle life of zinc electrodes. Herein, we propose a modulation strategy by constructing a preferentially adsorbed layer on the Zn surface and altering the solvation structure of Zn2+ to ensure uniform ion transport through introducing a bifunctional electrolyte additive, butyrolactam (BA). As demonstrated using experimental results, DFT calculations, and theoretical simulations, sustained water consumption and dendrite growth issues are efficiently resolved and highly reversible Zn plating/stripping is achieved. By virtue of this bifunctional additive, the symmetric cells deliver long-term stability for 6200 h at 0.5 mA cm-2, 3900 h at 1 mA cm-2, 2000 h at 2 mA cm-2 and 800 h at 10 mA cm-2. Even at a high current density of 80 mA cm-2, the symmetric cells present stable cycling over 1000 cycles. Compared to the baseline electrolyte, the BA-based electrolyte shows excellent zinc stripping/plating performance with an improved coulombic efficiency. The assembled Zn-V2O5 and Zn-I2 full cells show enhanced rate capability and cycling stability. The proposed synergistic modulation concept in this work might provide a promising alternative for developing stable Zn anodes. A bifunctional electrolyte additive enabling stable Zn metal anodes.