The influence of LiCl coexistence with Al electrodeposition was investigated in a dimethyl sulfone, DMSO 2 , bath containing AlCl 3 at 403 K. The electrochemical behaviors of Li and Al ions were examined using Pt electrodes in the bath and the deposition mechanism was analyzed by cyclic voltammetry, CV, with an Al reference electrode in the bath. The coexistence of LiCl in the AlCl 3 -DMSO 2 bath inhibited the cathodic current corresponding to Al deposition in the CV experiment. The amount of

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... . 500 μmol Al deposits was obtained in constant potential electrolysis for 1 h at -2 V in the bath with 10 mol% AlCl 3 . However, it decreased to 140 μmol Al in the bath with 10 mol% AlCl 3 and 5 mol% LiCl. It was clarified that LiCl addition led to the formation of Li(DMSO 2 ) + more than the formation of ( ) 3 2 3 Al DMSO + from NMR measurement for the baths. This results in the suppression of Al deposition because LiCl inhibits the formation of ( ) 3 2 3 Al DMSO + complex ions, which is said to be necessary for Al electrodeposition.