Revealing the Long-Term Stability of Amide-Based Electrolytes for Aluminum Electrodeposition Under Dry Air

Developing nonaqueous electrolytes that enable aluminum electrodeposition in the presence of oxygen remains a challenge. Our previous study revealed oxygen-induced electrodeposition failure in 1-ethyl-3-methylimidazolium chloride–AlCl 3 electrolytes, whereas aluminum electrodeposition remained feasible in acetamide–AlCl 3 even under dry air. Comparative analyses indicated that reactions involving electrochemically reduced oxygen play a critical role in differentiating the electrodeposition behavior of these electrolytes. However, oxygen-induced degradation may not appear in a single electrochemical test and can accumulate during repeated electrodeposition, potentially being overlooked by conventional short-term screening. This study examines amide-based AlCl 3 electrolytes, urea–AlCl 3 and benzamide–AlCl 3 , as candidates for durable electrolytes in dry air and demonstrates the necessity of long-term stability tests to detect oxygen-induced failure. Cyclic voltammetry indicated largely reversible aluminum deposition and dissolution for both electrolytes under argon and dry air, and the resulting aluminum films exhibited nearly identical morphology in both atmospheres after short-term tests. In contrast, pronounced oxygen effects emerged during repeated electrodeposition in dry air: uniform film morphology was maintained in urea–AlCl 3 , whereas gradual degradation occurred in benzamide–AlCl 3 . These results demonstrate that short-term experiments can miss oxygen-induced failure, highlighting the need for long-term electrodeposition tests to reliably evaluate aluminum electrolytes in dry air.