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.