Li_2CO_3をリチウム原料とするAl-Li合金の高効率電解製造 High efficient electrolytic production of Al-Li alloy by using Li_2CO_3 as a source of lithium
The behavior of Li<sub>2</sub>CO<sub>3</sub> in molten LiCl electrolyte has been studied to produce Al–Li alloys electrolytically by using Li<sub>2</sub>CO<sub>3</sub> as a source of Li. The Li<sub>2</sub>CO<sub>3</sub> is a promising raw material of lithium because of its low cost, non-hygroscopic property, high purity, etc. compared with LiCl. An anode compartment, which should prevent the cathode from the infiltration of the anolyte with keeping the electrical contact, was formed by using porous Al<sub>2</sub>O<sub>3</sub> crucible. By the electrolysis, lithium deposited at molten aluminum cathode to make an Al–Li alloy and the cathodic potential shifted to more positive potential than that of deposition of pure Li because of lower activity of Li in the alloy. On the other hand, the carbonate ion reacted with graphite anode and the anodic potential decreased by almost 1.2–1.3 V than that of Cl<sub>2</sub> evolution when feeding small pieces of Li<sub>2</sub>CO<sub>3</sub> into the anode compartment. Therefore, the potential required to obtain the Al–Li alloy is almost half of the theoretical decomposition potential of LiCl. Current efficiency of cathode was more than 90% which was comparable to the electrolysis using only LiCl electrolyte. Main component of the exhaust from the anode was CO<sub>2</sub> with small amount less than 3% of CO. Carbon consumption was almost the theoretical minimum which was 0.5 mol to one mol Li<sub>2</sub>CO<sub>3</sub>. These results suggest that the use of Li<sub>2</sub>CO<sub>3</sub> as a raw material of lithium is very effective to produce high-quality Al–Li alloy with low cost.
軽金属 48(3), 138-142, 1998-03-30
The Japan Institute of Light Metals