Electrodeposition of Al from Dimethyl Sulfone-Aluminum Chloride Baths Under Dry Air

Abstract

Electrodeposition of Al requires the use of a non-aqueous bath, and it is usually carried out under an inert gas atmosphere such as nitrogen and argon using a glove box to protect the bath from absorbing moisture. However, the operation of the electrodeposition process under such conditions reduces the producibility and increases the cost, hindering its industrialization. If Al electrodeposition can be carried out in dry air, it would facilitate the operation and drastically lower the process cost. In this study, we examine the feasibility of the electrodeposition of Al under dry air using an organic bath, dimethylsulfone (DMSO2)-AlCl3 system (1-6). The electrodeposition of Al was carried out at 110°C under dry air with a dew point of ~−60°C in a dry chamber. The electrodeposition was also carried out under Ar atmosphere using a glove box, and the deposits obtained under the two atmospheres were compared. Cyclic voltammetry and XRD analysis of the deposits confirmed that the Al metal can be electrodeposited from the DMSO2-AlCl3 bath even in dry air. However, the Al film obtained in dry air tended to have black spots and a rough surface with scratch-like non-deposited portions. In contrast, a uniform, flat, silver-white Al film covering entirely the surface of the substrate is electrodeposited in Ar atmosphere under the same conditions, except for the atmosphere. This poor appearance of the Al film electrodeposited in dry air could be resolved by adding an additive to the bath. The current efficiency for the Al electrodeposition was slightly lower in dry air than that in Ar atmosphere, but it was still higher than 90%.