Acetone CoSolvent Reconstructs the Zn²⁺ Solvation Sheath for Ultra-Stable Zinc-Ion Battery

The uncontrollable growth of zinc metal dendrites and the water-induced parasitic reaction in pure aqueous electrolyte cause the poor cycling stability of zinc ion battery. Herein, a stable electrode/electrolyte interface with a dendrite-free zinc anode is developed by adding acetone into the aqueous electrolyte. The as-formed water/acetone hybrid solvent effectively optimizes the Zn²⁺ solvation structure (coordinated water changes from 6 to 4) and induces the uniform zinc ion deposition through the high adsorption energy with the Zn (002) surface. It also stabilizes the zinc metal by reducing the corrosion reaction (hydrogen evolution) with water and the formation of a basic zinc salt by-product. As a result, the symmetrical cell with the acetone/water electrolyte exhibits a superior stability of 3700 h (154 days) at 1 mA cm⁻². The battery with the Na₂V₆O₁₆·3H₂O cathode delivers an 84.1% capacity retention after 1000 cycles at 1.0 A g⁻¹. The organic/aqueous electrolyte provides a new insight into understanding the relationship between solvation structure, electrode/electrolyte interface, and the performance of the zinc ion battery.