Reconstructing hydrogen bond networks to enable highly reversible iron metal anodes

Abstract

Aqueous batteries with Fe metal anodes have great potential for large-scale energy storage in power grids due to their low cost, abundance of iron and safety. However, their practical application is limited by the competing hydrogen evolution reaction (HER) during cycling and low coulombic efficiency (CE). This work explores the feasibility of the strategy of reconstructing the hydrogen bond network to suppress the HER and improve the Fe plating/stripping efficiency. Acetamide (Ace) as the reconstructing agent is added into the Fe electrolyte. The experimental results indicate that adding 2.0 mol L⁻¹ (M) Ace into 0.5 M Fe electrolyte leads to higher average CE (95.75%) in Fe ‖ Cu half-cells compared to the Fe electrolyte without Ace (78.03%). Further, 2.0 M Ace electrolyte inhibits the growth of competing lattice planes, and forms more crystalline Fe nuclei and denser growth during plating leading to highly compact and reversible Fe anodes. Therefore, the all-iron battery (composed of Cu precoated Fe as the anode and a carbon plate as the cathode) with 2.0 M Ace anode electrolyte exhibits stable cycling performance. This study provides further development for reconstructing the hydrogen bond network electrolytes for high efficiency Fe metal anodes.