Tailoring the solvation shells of dual metal ions for high-performance aqueous zinc ion batteries

For a long time, the issue of dendrites in neutral/mild electrolyte-based aqueous zinc-ion batteries (AZIBs) has been a matter of concern. The dendrites resulting from this problem lead to short-circuit faults and significantly reduce the cycle life, which is quite troublesome. Here, we induce uniform Zn deposition by utilizing the enhanced electrostatic shielding effect of a hybrid additive of Na2SO4 and EDTA. The limited tip-blocking effect of Na+ is due to the higher exchange reaction rate constant (kex) of water molecules in the solvation shell. The coordination of EDTA can provide a more stable solvation shell for Na+, ensuring a stronger blocking effect on Zn deposition at the tip. This enhanced electrostatic shielding effect effectively suppresses the growth of Zn dendrites. In addition, EDTA also enters the solvation shell of Zn2+ and displaces some coordinated water molecules, allowing for more reversible Zn plating/stripping without significant side reactions occurring at the Zn anode.