A Low‐Cost and Air‐Stable Rechargeable Aluminum‐Ion Battery

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 H2 O and five succinonitrile molecules coordinate with one Al3+ ion. The optimized ratio of Al(ClO4 )3 ·9H2 O 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.