Innovative electrochemical processing using molten salts

Abstract

Until recently, the only electrochemical applications using molten salts involved the direct electrolysis or electrorefining using molten salts in which the ion carrying the current was predominant in the molten electrolyte. In recent years, there has been a considerable amount of research into high temperature fuel cells and batteries and some of this technology is directly applicable to the molten salts processing of materials. Combining molten salts with solid electrolytes has led to novel processes for the preparation of sodium, magnesium and other metals. It is known that the alkaline earth chlorides dissolve substantial quantities of their own oxides, leading to electrolytes that are oxygen ion conductors, under certain conditions, and these electrolytes have been used to remove oxygen from oxide cathodes to give pure metals. Surprisingly, it has been found that when the cathodes consist of mixtures of alloys, the product is an alloy or intermetallic compound. This approach may offer a more cost effective way of preparing high value added materials. Intercalation of alkali and alkaline earth elements into oxides and graphite is discussed. The former could be used for the refining of metals and the latter for the preparation of carbon nanotubes.