In Situ Preparation of MXenes in Ambient-Temperature Organic Ionic Liquid Aluminum Batteries with Ultrastable Cycle Performance

A fluorine-free and water-free electrochemical preparation of MXenes is achieved in Lewis acidic molten salts at ambient temperature. In addition, the anode reaction of the MAX phase V2AlC is studied in the organic ionic liquid aluminum battery and the extraction voltages of the metal atoms Al and V in the MAX phase V2AlC are determined. This points out the direction for the constant-voltage electrochemical preparation of MXenes. Furthermore, the electrochemical performance of the etched V2AlC (E-V2AlC) in an aluminum battery is studied. The one-stop preparation-application process prevents the MXenes from contacting water and air, and the MXenes etched in the aluminum battery are more conducive to the intercalation/deintercalation of Al3+. Therefore, E-V2AlC exhibits excellent electrochemical performance in an aluminum battery. Under the conditions of a voltage window of 0.01-2.3 V (V vs Al/Al3+) and a current density of 500 mA g-1, the specific discharge capacity is about 100 mAh g-1 after 6500 cycles. In addition, the energy storage mechanism and Faraday energy storage method of E-V2AlC in an aluminum battery are studied. The diffusion coefficient D of Al3+ is determined by a galvanostatic intermittent titration technique. The reasons for its excellent electrochemical performance are clarified from the perspective of kinetics.