Green and low-cost acetate-based electrolytes for the highly reversible zinc anode

A highly concentrated solution of potassium, lithium and zinc acetate is proposed as green “Water-in-Salt” electrolyte (WiSE). In this halide-free electrolyte, investigated by classical Molecular Dynamics simulations, differential scanning calorimetry (DSC) and Raman spectroscopy, the water molecules are coordinated by the acetate anion as well as the various cations. As a result of the strong coordination of water molecules, the WiSE enables outstanding zinc (Zn) plating/stripping average Coulombic efficiency (CE) (99.6%) and long-term cycling stability. Dual ion cells using this electrolyte and featuring the Zn metal anode and either LiFePO4 (LFP) or spinel LiMn2O4 (LMO)-based cathodes deliver discharge capacity of 155 mA h g−1 and 121 mA h g−1 at 0.05C, respectively. The Zn/LFP cells demonstrate better cycling stability compared to Zn/LMO, which is attributed to the more stable crystal structure of LFP.