Electrodeposition of Al, Al-Li Alloy, and Li from an Al-Containing Solvate Ionic Liquid under Ambient Conditions

Abstract

Herein, inspired by previous reports on the electrochemical reduction of Al in diverse electrolyte systems, we describe a novel Al-containing solvate ionic liquid (2:1 (mol/mol) mixture of ethylene carbonate (EC) and AlCl3) that allows low-temperature electrochemical deposition of Al and features the advantages of low cost, ease of preparation, and high electrochemical stability. Electrodeposition of Al-Li alloy and Li can also be realized in this system. Additionally, the above ionic liquid exhibited a saturated vapor pressure of 0.0012 kPa and a conductivity of 1.32 mS/cm at 298 K, which was acceptable for practical applications. To elucidate the electrochemical deposition mechanism, the ionic components of the 2:1 EC/AlCl3 system were characterized by a range of instrumental analysis techniques and theoretical calculations, and Lewis-acidic cations were identified as the electroactive species for Al electrodeposition. Notably, an Al-Li alloy could be obtained by co-deposition in the new solvate ionic liquid, and Li metal could also be electrodeposited on a high-purity Al plate in the form of Al4Li9 and Li3Al2 under ambient conditions using LiCl as a Li source. Al-containing solvate ionic liquids, which to an extent evolved from organic-salts, are of increasing interest. They are expected to gain more attention in the field of electrochemical metallurgy of active metals, due to their higher tunability and lower price.