Highly Reversible, Grain-Directed Zinc Deposition in Aqueous Zinc Ion Batteries

Achieving highly reversible Zn metal anodes is a crucial step in advancing the performance of aqueous zinc ion batteries. However, despite the relative stability of Zn metal in aqueous environments, Zn metal is plagued by deterrents such as dendritic growth, H-2 evolution, and corrosion. This mainly stems from the absence of a stable solid-electrolyte interphase (SEI), an inevitable consequence of moderate concentration aqueous electrolytes. In response to such issues, herein, an artificial SEI formed from cross-linked gelatin is introduced by coating the surface of Zn metal. The presence of the gelatin layer significantly changes the deposition morphology of Zn, where its plated surface is much more uniform and dense compared to bare Zn metal. Interestingly, grain-directed electrodeposition can be observed in which the crystallographic orientation of the underlying Zn metal substrate determines the directionality of electrochemically plated Zn. This mode of growth results in a highly uniform and dense surface, translating to enhanced electrochemical stability.