The corrosivity of chloride-based electrolytes is a major shortcoming in the practical realization of rechargeable aluminum batteries. Herein, the effect of Cl − on Al speciation and electrochemistry in tetrahydrofuran (THF) was measured by employing theoretical and experimental approaches for three systems: Al(OTF) 3 /THF, Al(OTF) 3 plus LiCl in THF, and AlCl 3 /THF. The high consistency between measured and computed spectroscopic aspects associated with Al(OTF) 3 /THF electrolyte provided both a rationale for understanding Al complex-ion formation in a Cl − -free environment and an approach for examining the effect of Cl − on Al speciation. Room-temperature Al plating was achieved from dilute solutions ([Al] = 0.1 M) at potentials ≥ 0 V (vs Al/Al 3+ ). Cl − is found to enable facile Al plating and SEM reveals that Al is electrochemically deposited as nanocrystalline grains.
Exploring reliable electrolytes for aluminum ion batteries requires an in-depth understanding of the behavior of aluminum ions in ethereal-organic solvents. Electrolytes comprised of aluminum trifluoromethanesulfonate (Al-triflate) in tetrahydrofuran (THF) were investigated computationally and experimentally. Optimized geometries, redox potentials, and vibrational frequencies of species likely to be present in the electrolyte were calculated by density functional theory and then measured spectroscopically and electrochemically. Aluminum appears to be electrochemically active in THF with a reduction onset near 0 V versus Al/Al 3+ . Spectroscopic measurements reveal explicit evidence for the presence of two concentrationdependent ionic environments for the triflate anions, namely, outer-shell ligands and Al-bound triflates. Additionally, ionic conductivities of ∼2.5 mS/cm were measured for these electrolytes ∼0.8M.
The corrosivity of chloride-based electrolytes is a major shortcoming in the practical realization of rechargeable aluminum batteries. Herein, the effect of Cl- on Al speciation and electrochemistry in tetrahydrofuran was measured by employing theoretical and experimental approaches for three systems: Al(OTF)3/THF, Al(OTF)3 plus LiCl in THF, and AlCl3/THF. The high consistency between measured and computed spectroscopic aspects associated with Al(OTF)3/THF electrolyte provided both a rationale for understanding Al complex-ion formation in a Cl- free environment and an approach for examining the effect of Cl- on Al speciation. Room-temperature Al plating was achieved from dilute solutions ([Al] = 0.1M) at potentials ≥ 0V (vs. Al⁄Al3+). Cl- is found to enable facile Al plating and SEM reveals that Al is electrochemically deposited as nanocrystalline grains.
In the quest for developing rechargeable aluminum (Al) batteries, reversible Al electrodeposition in the absence of active-halide components (haloaluminate complexes such as, Al2Cl7–, AlCl4–, solvated AlCl3, and halide-anions such as, F–, Cl–) is considered an immense challenge. For this reason, the choice of electrolyte has been primarily limited to the highly corrosive chloroaluminate systems based on aluminum trichloride (AlCl3). In this work, we demonstrate reversible room-temperature Al plating from an active-halide-free (AHF) organic electrolyte based on aluminum trifluoromethanesulfonate (Al(OTF)3) and compare it to the AlCl3-based organic electrolytes. Cyclic voltammetry measurements on a gold working electrode reveal oxidative stability of ca. 1.8 V (vs Al/Al3+). From insights obtained by DFT and FTIR, ionic speciation in the electrolyte is explored, and mechanisms for the underlying electrochemical processes in the OTF–-based electrolytes are proposed. Al electrodeposition and stripping were confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray Diffraction (XRD) spectroscopy. Characterizing the Al deposits from either the OTF–- or the Cl–-based electrolytes via depth-profile X-ray Photoelectron Spectroscopy (XPS) analyses, we find that these deposits consist of metallic Al, aluminum oxide (Al2O3), and either aluminum trifluoride (AlF3) or aluminum trichloride (AlCl3) contaminants arising from a reaction with the electrolyte components which occurs during the electrodeposition process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.