Investigation of the Hybrid Electrolyte 12 M Zn(NO₃)₂·4H₂O-ACN for Use in Zinc-Ion Batteries

Document Type : Original Articles

Author

Farzad Soleimani

Department of Metallurgy Engineering, Payame Noor University, Tehran,

10.22067/jmme.2025.92130.1187

Abstract

"Water-in-salt" electrolytes, with their wide electrochemical stability window, are a significant advancement in aqueous batteries and supercapacitors. However, their efficiency is often hindered by the slow diffusion kinetics of metal ions like lithium or zinc. To overcome this limitation, a hybrid aqueous/non-aqueous electrolyte can be formed by introducing an organic co-solvent into the aqueous solution. This approach accelerates the diffusion of metal ions and resolves kinetic challenges. In this study, the physicochemical characteristics of the hybrid electrolyte system (1-x) 12 M Zn(NO₃)₂·4H₂O-xACN were examined. The addition of 10 wt% acetonitrile to the aqueous 12 M Zn(NO₃)₂·4H₂O improved the solvation structure, restricted O-H bonding, reduced the number of free O-H bonds, and strongly hydrated Zn²⁺ ions, leading to enhanced electrical conductivity. Electrochemical tests with CuHCF electrodes showed high reversibility, an initial capacity of 91 mAh/g, and over 90% capacity retention after 100 cycles. Rate capability analysis revealed significant kinetic improvements, with 80% capacity retention even after a 20-fold charge rate increase in the presence of 10 wt% acetonitrile. Furthermore, electrochemical impedance spectroscopy (EIS) confirmed a 20-fold increase in the Zn²⁺ ion diffusion coefficient compared to the aqueous electrolyte.

Keywords

Zinc-Ion Battery

Hybrid Electrolyte

Solvation Structure

Electrochemical Reaction Kinetics

Subjects

• Electrochemistry

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