Slowing Down Zinc Electrodeposition Kinetics Can Maximize and Compromise Anode Stability: How Slow Is Too Slow?

Area of Science:

• Electrochemistry
• Materials Science

Background:

• Aqueous zinc metal batteries (AZMBs) offer safe and low-cost grid storage solutions.
• Poor zinc anode reversibility, due to hydrogen evolution and dendrites, hinders AZMB performance.
• Additive-induced kinetic suppression can paradoxically lead to anode instability in AZMBs.

Purpose of the Study:

• To establish a framework for optimizing additive concentration in AZMB electrolytes.
• To elucidate the mechanistic origin of anode instability beyond critical additive concentrations.
• To provide a rational basis for designing stable AZMB electrolytes.

Main Methods:

• Systematic tuning of solvation environments in ZnSO4, ZnCl2, and Zn(OTf)2 electrolytes.
• Investigation of the interplay between electrodeposition, nucleation-growth, and corrosion kinetics.
• Analysis of zinc deposition morphology and hydrogen evolution suppression.

Main Results:

• An optimal kinetic window for additive concentration was identified, enhancing AZMB stability.
• Within this window, (002)-oriented zinc deposition suppressed hydrogen evolution, improving reversibility.
• Beyond the optimal window, reduced deposition kinetics led to corrosion-dominated behavior and accelerated hydrogen evolution.

Conclusions:

• Electrolyte stability in AZMBs arises from a synergistic balance of deposition, nucleation, and corrosion kinetics.
• The established framework guides electrolyte design for improved AZMB performance and longevity.
• This approach is generalizable for additives modulating Zn2+ solvation without impacting mass transport.