A dual-functional rare earth halide additive for high-performance aqueous zinc ion batteries

Aqueous zinc ion batteries have received much attention due to their high theoretical capacity, inherent safety, and low cost. However, the growth of zinc dendrites and side reactions hinder its practical application. In this study, a rare-earth metal salt, europium chloride (EuCl 3 ), is used as a new electrolyte additive to regulate the uniform deposition of zinc and inhibit the interfacial side reactions. The EuCl 3 additive benefits for preferentially Zn 2+ deposition along the (002) crystal plane, as well as suppress the hydrogen evolution reaction (HER) at electrode-electrolyte interface. As a result, the capacity retention of the Zn//NaV 3 O 8 full cell assembled with the modified electrolyte much better than that without additives, showing a long-term cycling life and high coulombic efficiency at a current density of 10 A g −1 . This new dual-functional rare earth halide additive strategy provides great potential for the development of practical aqueous zinc ion batteries and other battery systems. • EuCl 3 was introduced for the first time to the electrolyte of zinc ion battery. • Eu 3+ forms a dynamic electrostatic shielding layer to regulate Zn 2+ deposition. • The optimized EuCl 3 electrolytes enable longer cycle life of zinc ion batteries.