Can metallic lithium be electrochemically extracted from water, the universal solvent?

Abstract

The electrochemical extraction of reactive metals, such as Li, Mg, Al, Ti, and rare-earth metals, from different electrolyte systems at low temperatures has been a longstanding challenge in the field of electrochemical extractive metallurgy. Water is an excellent green solvent; therefore, the electrodeposition of aqueous solutions of reactive metals would be more sustainable than traditional approaches involving molten salts and organic solvents. Inspired by the successful application of water-in-salt electrolytes for battery chemistry, we attempted the electrochemical extraction of metallic Li from water via its deposition on different substrates. We found that Li can be electrodeposited in the form of Li-based alloys and hydroxides, as identified by X-ray diffraction and X-ray photoelectron spectroscopy analysis, under certain conditions, and the mechanisms behind the observed electrochemical behaviour are discussed using different characterisation techniques and density functional theory calculations. In addition, the prospects for the electrodeposition of reactive metals from aqueous solutions are considered, and suggestions for further study are made. Thus, this work provides important insights regarding the electrochemical extraction of reactive metals from water at room temperature, and we believe that this work forms a basis for the development of safer batteries, as well as advanced electrodeposition and electrometallurgy technology.