Rechargeable Iron-Ion Battery Using a Pure Ionic Liquid Electrolyte

Yansong Zhao; Yingpeng Zhen; Tobias Boström

doi:10.1021/acsomega.1c06170

Rechargeable Iron-Ion Battery Using a Pure Ionic Liquid Electrolyte

ACS Omega. 2022 Jul 7;7(28):24082-24090. doi: 10.1021/acsomega.1c06170. eCollection 2022 Jul 19.

Authors

Yansong Zhao¹, Yingpeng Zhen², Tobias Boström³

Affiliations

¹ Department of Safety, Chemistry and Biomedical Laboratory Sciences, Faculty of Engineering and Science, Western Norway University of Applied Sciences (HVL), 5020 Bergen, Norway.
² Department of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway.
³ Renewable Energy Group, Department of Physics and Technology, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway.

Abstract

A rechargeable iron-ion battery (Fe-ion battery) has been fabricated in our laboratory using a pure ionic liquid electrolyte. Magnetic ionic liquids of 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl₄) and 1-methyl-3-octylimidazolium tetrachloroferrate (OmimFeCl₄) are synthesized and utilized as electrolytes in this work. The chemical structure of the two ionic liquids (ILs) is investigated using Raman analysis. In addition, the physical and thermal stability properties of the ionic liquid (IL) BmimFeCl₄, including density, viscosity, melting point, and decomposition temperature, are investigated using a density meter, viscosity meter, differential scanning calorimeter, and thermogravimetric analyzer. Moreover, the electrochemical properties, including electrochemical window, and ionic conductivity of the IL BmimFeCl₄ are investigated using an electrochemical instrument and a conductivity meter. It is found that the magnetic IL BmimFeCl₄ has good physical and electrochemical properties to be utilized as an electrolyte for iron-ion battery fabrication. Iron-containing materials, including pure iron foil, carbon-coated iron nanoparticles, and iron powder, are used as a cathode in the Fe-ion battery. The anode of the Fe-ion battery is graphite. Electrochemical properties of full cells are investigated, including cyclic voltammetry curves and specific charge-discharge capacity. The Fe-ion battery is a unique rechargeable ion battery with magnetic ions. In addition, pure IL BmimFeCl₄ is utilized as an electrolyte in this Fe-ion battery. IL BmimFeCl₄ is stable and almost nonvolatile. Therefore, an Fe-ion battery with a pure IL electrolyte is safer than that with an organic electrolyte. An Fe-ion battery using a pure IL electrolyte is a promising battery with many potential applications.