Hydride-Enhanced Plating and Stripping of Aluminum from Tri-flate -Based Organic Electrolytes

In the quest for developing rechargeable Al batteries, reversible Al electrodeposition in the absence of active-halides is con-sidered an immense challenge. For this reason, the choice of electrolyte has been primarily limited to the highly corrosive chloroaluminate systems based on AlCl3. In this work, we demonstrate reversible room-temperature Al plating from an ac-tive-halide-free organic electrolyte based on Al(OTF)3 and compare it to the AlCl3-based organic electrolytes. Cyclic volt-ammetry measurements on a gold working electrode reveal oxidative stability of ca. 1.8 V (vs Al/Al3+), and a side reaction likely involving the oxidative generation of H2. From insights obtained by DFT and FTIR, a mechanism for the underlying electrochemical process in the OTF–-based electrolytes is proposed. Al electrodeposition was confirmed by optical microsco-py, SEM and XRD. Characterizing the Al deposits from either the OTF–- or the Cl–-based electrolytes via depth-profile XPS analyses, we find that these deposits consist of metallic Al, Al2O3, and either AlF3 or AlCl3 contaminants arising from a reac-tion with the electrolyte components which occurs during the electrodeposition process.