Amide-based Al electrolytes and their application in Al metal anode-organic batteries

Abstract

Aluminum rechargeable batteries are seen as a next-generation battery technology based on abundant materials. However, the current standard Al electrolytes are based on expensive ionic liquids. In this paper, the potential use of three AlCl₃/amide-based electrolytes is investigated as a low-cost alternative from the perspective of Al metal anode and organic cathode compatibility. Our investigation shows the promising electrochemical performance of amide electrolytes and specific differences between the electrolytes depending on amide alkyl chain length. In particular, amides with longer alkyl chains show better plating/stripping efficiency and lower overpotential compared to the shorter acetamide one. Similarly, organic cathode capacity retention is the best for the electrolyte with the longest alkyl chain. However, the cathode capacity retention is subpar to the standard ionic liquid-based Al electrolyte although it undergoes the same electrochemical mechanism of carbonyl bond reduction. Interestingly, there is no deterioration of the anthraquinone redox peak through the appearance of a side peak at a lower potential in amide-based electrolytes, which is observed in standard electrolyte based on ionic liquid. Amide-based electrolyte display promise for practical applicability, however, the low oxidation stability of amide-based electrolytes is identified as one of their key limitation and should be addressed in future work.