A Novel Moisture-Insensitive and Low-Corrosivity Ionic Liquid Electrolyte for Rechargeable Aluminum Batteries

Rechargeable aluminum batteries (RABs) are extensively developed due to their cost-effectiveness, eco-friendliness, and low flammability and the earth abundance of their electrode materials. However, the commonly used RAB ionic liquid (IL) electrolyte is highly moisture-sensitive and corrosive. To address these problems, a 4-ethylpyridine/AlCl₃ IL is proposed. The effects of the AlCl₃ to 4-ethylpyridine molar ratio on the electrode charge–discharge properties are systematically examined. A maximum graphite capacity of 95 mAh g⁻¹ is obtained at 25 mA g⁻¹. After 1000 charge–discharge cycles, ≈85% of the initial capacity can be retained. In situ synchrotron X-ray diffraction is employed to examine the electrode reaction mechanism. In addition, low corrosion rates of Al, Cu, Ni, and carbon-fiber paper electrodes are confirmed in the 4-ethylpyridine/AlCl₃ IL. When opened to the ambient atmosphere, the measured capacity of the graphite cathode is only slightly lower than that found in a N₂-filled glove box; moreover, the capacity retention upon 100 cycles is as high as 75%. The results clearly indicate the great potential of this electrolyte for practical RAB applications.