Towards Chloride-Free Organic Electrolytes for Rechargeable Aluminum Batteries

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.