LAUSR

Rechargeable aluminum‐ion batteries (AIBs) are promising for large‐scale energy storage due to the abundant reserves, low cost, and high capacity of the Al anode. However, the development of AIBs is currently hindered by the usage of AlCl3/1‐ethyl‐3‐methylimidazolium chloride electrolyte, which is expensive, highly corrosive, and extremely air‐sensitive. Herein, a new hydrated eutectic electrolyte (HEE) composed of hydrated aluminum perchlorate and succinonitrile for low‐cost, noncorrosive, and air‐stable AIBs is reported. Crystal water in the hydrated aluminum perchlorate plays a vital role in forming the HEE, in which one H2O and five succinonitrile molecules coordinate with one Al3+ ion. The optimized ratio of Al(ClO4)3·9H2O to succinonitrile is 1:12. When combining with the self‐doped polyaniline cathode, the associated AIB delivers a high discharge capacity of 185 mAh g−1 over 300 cycles; and the charge/discharge mechanism in the HEE is studied experimentally and theoretically. The HEE is nonflammable, air‐stable, and noncorrosive, thus enabling good air tolerance and facile fabrication of AIBs.