High-Voltage and Noncorrosive Ionic Liquid Electrolyte Used in Rechargeable Aluminum Battery

As a promising post-lithium battery, rechargeable aluminum battery has the potential to achieve a three-electron reaction with fully use of metal aluminum. Alternative electrolytes are strongly needed for further development of rechargeable aluminum batteries, because typical AlCl₃-contained imidazole-based ionic liquids are moisture sensitive, corrosive, and with low oxidation voltage. In this letter, a kind of noncorrosive and water-stable ionic liquid obtained by mixing 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]OTF) with the corresponding aluminum salt (Al(OTF)₃) is studied. This ionic liquid electrolyte has a high oxidation voltage (3.25 V vs Al³⁺/Al) and high ionic conductivity, and a good electrochemical performance is also achieved. A new strategy, which first used corrosive AlCl₃-based electrolyte to construct a suitable passageway on the Al anode for Al³⁺, and then use noncorrosive Al(OTF)₃-based electrolyte to get stable Al/electrolyte interface, is put forward.