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. A new moisture‐insensitive and low‐corrosivity Al2Cl7−‐free 4‐ethylpyridine/AlCl3 ionic liquid electrolyte is proposed. In situ synchrotron X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy mapping confirm that a stage‐3 graphite intercalation compound forms at the end of charging and that the deintercalation of AlCl4− occurs upon discharging, allowing a reversible capacity of 95 mAh g−1 and great cycleability.