Effect of Imidazole on kinetics of zinc metal electrodeposition in aqueous solution

Abstract

Electrochemical energy storage systems are critical in certain ways for a smooth transition from non-renewable to renewable energy sources. Zn-based batteries are one of the promising alternatives to the existing state-of-the-art Li-ion battery technology, since Li-ion batteries pose significant drawbacks in terms of safety and cost-effectiveness. Zn (reduction potential: -0.76 V vs. SHE) has a higher theoretical capacity compared to that of Li (820 mAh/g and 5854 mAh/cm3), which is certainly less expensive, safer, and more earth-abundant. The formation of dendrites, hydrogen evolution, and the formation of a ZnO passivation layer on the Zn anode are the primary issues in the development of rechargeable zinc batteries.The role of imidazole as an electrolyte additive in 2M ZnCl2 to prevent dendrite formation during zinc electrodeposition is investigated in this study. To characterise the efficacy and identify the appropriate concentration of imidazole, LSV and CA with in-situ monitoring of the electro-deposited zinc are used. The addition of 0.025 wt% imidazole to 2M ZnCl2 increases the cycle life of Zn-symmetric cells cycled at 1mA/cm2 for 60 minutes of plating and stripping from 90 to 240 hours. A higher value of the nucleation overpotential in the presence of imidazole suggests that imidazole gets adsorbed on the surface of zinc and suppresses the zinc electrodeposition kinetics, thus suppressing the formation of dendrites. X-ray tomography demonstrated short-circuit as the main-plausible failure mechanism of Zn symmetric cells, which is caused by dendrite formation. It was observed that the electrodeposition of zinc is more homogeneous when imidazole is present, and its presence in the electrolyte inhibits the production of a passivating coating (ZnO) on the Zn surface, preventing corrosion.