Understanding and Controlling the Nucleation and Growth of Zn Electrodeposits for Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries (AZBs) have been proposed as one of the most promising electrical energy-storage systems due to their low cost, high safety, environmental friendliness, and high energy density. However, their application is impeded by the Zn dendrite growth, which may puncture the separator, causing an internal short circuit. Although numerous efforts have been devoted to alleviating dendrite issues by structural design, surface modification, or electrolyte optimization, there are few works focusing on the fundamental research to understand the formation of Zn dendrites, which is critical to address the dendrites issue. In this work, we have systematically investigated the nucleation and growth behaviors of Zn on a stainless steel substrate. We reveal the dependence of Zn growth morphology on cycling conditions (current density and areal capacity) and further elucidate the intricate correlation with cycle life. It is observed that higher current density corresponds to higher nuclei density with a smaller size of zinc deposits and lower areal capacity render smaller zinc flakes, which contributes to the long cycle life of Zn-ion batteries. Based on these findings, a seeding protocol is then proposed to improve the uniformity and compaction of the Zn electrode. The methodology and findings here can potentially be applied to study the nucleation and growth of other metals.