Influence of Substrates on the Electrochemical Deposition and Dissolution of Aluminum in NaAlCl4 Melts.

The deposition and dissolution of aluminum in NaAlCl4 melts saturated with NaCl have been investigated by voltammetryand potentiometry for different electrode materials at 175°C. The tungsten and glassy carbon electrodes are shownto be electrochemically inert in the melts, whereas copper is electrochemically active; it dissolves into the melts at a lowanodic potential. On a nickel substrate, nickel dichloride will be formed at a potential of ca. 1.0 V vs. an aluminum referenceelectrode. The reversibility (of deposition and dissolution of aluminum) is found to be strongly affected by currentdensity and the coulombic charges used for glassy carbon electrodes, mainly because of poor adhesion of the deposits tothe substrate. The reversibility is noticeably affected by the magnitude of deposition current density for the tungsten electrodes,while it remains high on the nickel electrode under all conditions investigated. Nickel and, to some extent,tungsten electrodes proved to be appropriate as working anodes in the Al/NaCl-AlCl3/Ni battery system.