Non‐fluorinated Zinc Anions: A Low‐Cost Environmental Approach for Reversible Zinc Electrochemistry

Abstract

AbstractRechargeable zinc batteries (RZBs) are of immense interest as low‐cost and sustainable energy storage devices. However, formation of Zn dendrites, Zn corrosion, and undesired side reactions in aqueous electrolytes as well as the use of costly fluorinated salts in organic electrolytes, have hindered the commercialization of RZBs. In this work, a cost‐efficient and environmentally friendly, non‐aqueous electrolyte comprised of zinc dicyanamide (Zn(dca)2) in dimethyl sulfoxide (DMSO) is shown to support the electrochemical cycling of zinc. Fourier‐transform infrared (FT‐IR) spectroscopy complemented with theoretical studies suggest that the solvation of Zn2+ is stabilized with both [dca]− anions and DMSO molecules at high concentrations (≥1.0 M) of the zinc salt content. Stable charge/discharge cycles in zinc symmetrical cells with low overpotentials (0.05 V) were especially observed for 1.0 M Zn(dca)2/DMSO over 90 cycles at 1.0 mA cm−2 with scanning electron microscopy (SEM) images confirming the formation of a dense and smooth zinc morphology on metal anode surface post‐cycling. X‐ray photoelectron spectroscopy (XPS) also shows that the presence of zinc nitride (Zn3N2) helps form a stable SEI layer in the presence of 1.0 M and 2.5 M systems, making [dca]‐based electrolytes highly promising candidates in rechargeable zinc batteries.