Aluminum Bis(trifluoromethanesulfonyl)imide as a Chloride-Free Electrolyte for Rechargeable Aluminum Batteries

Aluminum bis(trifluoromethanesulfonyl)imide (Al(TFSI)3) was synthesized by a simple substitution reaction and investigated as the Al3+ source for the electrolyte of a rechargeable Al battery. The electrochemical window was extended to 3.6 V with the electrolyte containing Al(TFSI)3 in AN, whereas it was ∼2.5 V with the conventional electrolyte for the Al rechargeable battery. A reversible electrochemical Al deposition/dissolution reaction was observed on a Mo plate electrode with small overpotential less than 0.5 V. NMR and Raman spectra identified the main Al species in the electrolyte as Al(TFSI−)x(AN)6-x3-x (x = 1 ∼ 6).