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 H 2 O 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 H 2 O 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 2+ and bond with solvated H 2 O molecules. Simultaneously, PCA - anions also induce the construction of H-bonds between free H 2 O molecules and them. Therefore, the activity of free and solvated H 2 O 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 H 2 O 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.