Ion solvation modulating via Imidazolidinyl urea additive for stable Zn2+deposition

The development of energy conversion and storage equipment is a necessary guarantee for social development, and aqueous Zn-ion batteries have become a promising alternative to Li-ion batteries due to its high safety, environmental friendliness, and low cost. However, aqueous Zn-ion batteries suffer from the dendrite growth and parasitic reactions, which hinder the wide application of the batteries. In this paper, imidazolidinyl urea (IDU) is added to aqueous electrolytes because of the special structural properties of IDU. The effects of IDU as an additive on battery stability are elucidated through theoretical modelling, calculations, and experimental validation. Firstly, the effect of concentration on the ion transport properties of the electrolyte was obtained by modelling and calculating the Zn2+ diffusion coefficient and ionic conductivity of electrolytes with different concentrations of IDU added. In addition, the optimal IDU addition concentration was achieved by verification of cycling experiments in Zn symmetric cells. Moreover, it was confirmed using in situ deposition experiments that the addition of IDU could participate in the coordination of Zn2+ into the solvated layer of Zn2+, thereby accelerating the desolvation process of Zn2+, and further improving the uneven deposition of Zn on the negative electrode surface and the growth of dendrites. Finally, it was verified that the IDU addition could enhance the cycle life and stability of the battery, maintaining an efficiency of about 95 % and a specific capacity of discharge of 90 mAh center dot g-1 after more than 1000 cycles in a full cell assembled from Zn flakes and improved iodine electrodes.