High current density, efficient cycling of Zn2+ in 1-ethyl-3-methylimidazolium dicyanamide ionic liquid: The effect of Zn2+ salt and water concentration

The electrodeposition and dissolution of Zn2+ have been investigated in 1-ethyl-3-methylimidazolium dicyanamide [emim][dca] ionic liquid to support the development of Zn-based secondary batteries. Cyclic voltammetry indicates that the zinc salt dissolved in the ionic liquid (IL) is a critical factor in the observed Zn/Zn2+ electrochemistry. The Zn2+ salt anions were found to have varying interaction strengths with the dissolved Zn2+ species in the order dicyanamide < sulfate < chloride < acetate. The concentration of water was found to be a crucial parameter for obtaining a uniform, dendrite free morphology when depositing zinc at a potential of − 2.15 V vs. Fc0/+. When deposited on glassy carbon, Zn(dca)2 in [emim][dca] displays high current densities and efficiencies appropriate for use in energy storage applications and has been found to allow the deposition of zinc metal in uniform, non-dendritic morphologies.

► Anion and H2O effects on Zn/Zn(II) electrochemistry in ionic liquid were investigated.
► Doping salt anion was found to drastically effect Zn redox electrochemistry.
► 3 wt% H2O was found to yield uniform, smooth zinc metal deposits in ionic liquid.
► Absence of water yields poor, porous zinc metal deposits.
► Zn(dca)2/ionic liquid electrolyte yields very high current densities (45 mA cm− 2).