Investigating the Zinc Deposition Behavior in Aqueous Zinc-Ion Batteries with PEG/Cellulose/ZnCl₂ Water-In-Salt Electrolytes via a Homemade Visualized Three-Electrode Tubular Cell

Abstract

Zinc (Zn) metal anodes have been extensively investigated in aqueous Zn-ion batteries (AZIBs). Nevertheless, severe dendrite issues caused by uneven ion diffusion and Zn deposition greatly influence the stability and safety of AZIBs. Herein, a novel three-electrode tubular cell assembled from simple materials is constructed for both electrochemical measurement and visual characterization. Measured by the tubular cell, a water-in-salt electrolyte (WiSE) exhibits excellent ionic conductivity (33.29 mS cm –1 ) and reduced corrosivity, which is prepared by incorporating cellulose and polyethylene glycol (PEG) into concentrated zinc chloride (ZnCl 2 ) solution. The results reveal that the functional groups of cellulose and PEG in WiSE can regulate the solvation structure of Zn 2+, thereby alleviating consecutive side reactions and inhibiting the formation of byproducts. The inherent ion channels formed by the polymer chains and the physical barriers constructed by PEG on the Zn surface further facilitated the uniform deposition of Zn 2+ along the (002) crystal plane, enabling the Zn symmetric battery to achieve an ultralong cycle life of 1000 h at a current density of 2 mA cm –2 .