The Construction of Anion-Induced Solvation Structures in Low-concentration Electrolyte for Stable Zinc Anodes.

Aqueous zinc-ion batteries (ZIBs) are promising large-scale energy storage devices because of their low cost and high safety. However, owing to the high activity of HO molecules in electrolytes, hydrogen evolution reaction and side reactions usually take place on Zn anodes. Herein, additive-free PCA-Zn electrolyte with capacity of suppressing the activity of free and solvated HO molecules was designed by selecting the cationophilic and solventophilic anions. In such electrolyte, contact ion-pairs and solvent-shared ion-pairs were achieved even at low concentration, where PCA anions coordinate with Zn and bond with solvated HO molecules. Simultaneously, PCA anions also induce the construction of H-bonds between free HO molecules and them. Therefore, the activity of free and solvated HO molecules is effectively restrained. Furthermore, since PCA anions possess a strong affinity with metal Zn, they can also adsorb on Zn anode surface to protect Zn anode from the direct contact of HO molecules, inhibiting the occurrence of water-triggered side reactions. As a result, plating/stripping behavior of Zn anodes is highly reversible and the coulombic efficiency can reach to 99.43 % in PCA-Zn electrolyte. To illustrate the feasibility of PCA-Zn electrolyte, the Zn||PANI full batteries were assembled based on PCA-Zn electrolyte and exhibited enhanced cycling performance.