Balanced electrochemical reaction kinetics and mass transfer for stable zinc negative electrode.

Abstract

The formation of zinc dendrites is a significant obstacle to commercializing zinc-ion batteries. Although the discrepancy between the fast electrochemical reaction kinetics and the comparatively sluggish mass transfer leads to the formation and growth of dendrites, a profound understanding of how the relationship between the two factors influences dendrite formation is essential. Here, through investigating a series of urea derivatives for regulating Zn²⁺ plating, we find that achieving a better balance between electrochemical reaction kinetics and the mass transfer rate is crucial for effectively suppressing dendrite formation. A dimensionless constant, K, is proposed to quantify the balance between these two factors. As a result, the electrolyte with N, N-dimethylurea has the highest K value, enabling cumulative capacities of 11,000 mAh cm^-2 for Zn | |Zn cells and 7,500 mAh cm^-2 for Zn | |Cu cells achieved at a current density of 10 mA cm^-2. Furthermore, the Zn | |Zn_0.25V₂O₅·nH₂O pouch cell with a mass loading of 60 mg cm^-2 delivers a capacity of 6.95 Ah and demonstrates stable cycling performance using the modified electrolyte. This work provides theoretical insights into governing the formation and growth of zinc dendrites.