Functionalizing the interfacial double layer to enable uniform zinc deposition

Due to the unsatisfactory electrode/electrolyte interface, the metallic Zn dendrites and corrosion are easily induced, severely hindering the applications of zinc-ion batteries (ZIBs). Herein, a strategy that engineers the interfacial double layer by an extremely low concentration of sulfolane is proposed to tune the Zn stripping/plating behavior. It is revealed that the highly-polar sulfolane can predominately occupy the inner Helmholtz layer over water, and then regulate the upcoming Zn 2+ to directly deposit downward. Simultaneously, the widened Helmholtz layer can weaken the electric field intensity, which will generate more nucleation sites and reduce the nuclei radius, thereby promoting uniform zinc deposition as well. Moreover, corrosion byproducts can be inhibited since fewer water molecules can contact the Zn electrodes. Consequently, the battery performance can be naturally optimized. With an optimum amount of sulfolane, the Zn∥Zn battery can operate for more than 1,100 h under 1 mA cm −2 and 1 mAh cm −2 . And the as-constructed Zn∥NaV 3 O 8 ·1.5H 2 O battery demonstrates considerably higher cycling stability than that without sulfolane. Overall, this work has provided a deep insight into constructing a functional interfacial double layer to regulate zinc deposition, which can also act as a reference for other metal-based batteries.