Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies

Abstract

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed.

Scientific Challenges and Improvement Strategies of Zn‐Based Anodes for Aqueous Zn‐Ion Batteries

“…Huy et al discussed issues and prominent progresses of Zn anodes in aqueous. [18] Zhang et al summarized the analytical techniques for ZIBs. [19] Shi et al reviewed recent progresses and issues from the perspective of cathodes.…”

Electrolyte engineering strategies for regulation of the Zn metal anode in aqueous Zn‐ion batteries

“…Furthermore, due to the high safety demands of commercial batteries, aqueous‐compatible electrolyte batteries have begun to attract attention and thus suggest a further benefit of using a less reactive metal anode chemistry. Compared to other metal anodes that are compatible with aqueous electrolytes, such as Cu and Fe, Zn metals exhibit considerable merits, including stable electrochemical activity, low cost, and environmental friendliness 6–14 . The Zn metal anode in the aqueous zinc ion battery (AZB) has a suitable equilibrium potential (−0.76 V vs. standard hydrogen electrode) and delivers a high volumetric capacity of 5855 mAh cm −3 15–22 …”

Inhibition of Zinc Dendrites Realized by a β-P(VDF-TrFE) Nanofiber Layer in Aqueous Zn-Ion Batteries

“…However, due to the high cost, toxicity, and flammability of LIBs, environmentally friendly and nonflammable aqueous alternatives to LIBs have attracted considerable interest [ 8 , 9 , 10 , 11 , 12 ]. Among the various types of aqueous batteries, Zn-ion batteries (ZIBs) have been intensely studied as next-generation energy storage devices due to their high specific capacity (825 mAh g −1 ), low redox potential (−0.76 V vs. SHE), high abundancy of Zn metal, and low costs [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. However, Zn dendrite formation during battery operation can cause an internal short-circuit and lead to severe problems in terms of cell performance and safety.…”