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

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 | |Zn0.25V2O5·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. Zinc-ion batteries are promising for safe energy storage but suffer from zinc dendrite growth. Here, authors find that the balance between electrochemical reaction kinetics and mass transfer is crucial for suppressing dendrites and enabling stable Zn negative electrodes.