Electrowinning of Lithium from LiOH in Molten Chloride

An investigation was carried out to determine the viability of electrowinning lithium from LiOH in molten chloride, with a view to developing a system for the storage and transportation of hydrogen using LiH as the storage medium. It was predicted from the chemical potential diagram for the Li–O–H system that Li metal cannot be electrowon from a LiOH-containing salt, as any Li generated by electrolysis will readily react with LiOH to form Li2O. Electrolysis in molten LiCl–42 mol% KCl or molten LiCl–17 mol% KCl–26 mol% CsCl was therefore utilized, in which LiOH was fed into an anode compartment separated from the Li metal deposited at the cathode by a porous magnesia diaphragm, thereby preventing the transportation of LiOH into a cathode compartment. Using this arrangement, Li metal was successfully obtained with a cathode current efficiency of 84–86%. The generation of CO2 at the graphite anode was also found to decrease with decreasing electrolysis temperature when using a chloride melt with a lower eutectic temperature.