An π-conjugated organic cathode with multiple cyano-substituted for stable aqueous aluminum batteries.

Aqueous organic aluminum batteries (AOABs) are increasingly becoming a focal point for next-generation large-scale energy storage solutions due to their safety, reliability, and structural diversity. However, the development of organic molecules is hindered by their low electron affinity and slow molecular dynamics. To address these drawbacks, a high-electrophilicity organic molecule, DQP-6CN was synthesized. Surprisingly, the introduction of cyano-substituted compounds not only provided additional redox sites to increase specific capacity but also significantly enhanced stability during cycling by extending the π-conjugation. Ex-situ tests and density functional theory (DFT) revealed the unique coordination mechanism between the cyano group (CN) and Al(OTF) ions. Moreover, the introduction of the cyano group reduced coulomb repulsion between electrons by lowering the local electron density of the molecule, significantly improving the rate performance, as further validated by electrochemical testing and theoretical simulations. Consequently, it delivers a high discharge specific capacity of 279 mAh g at 400 mA g, excellent rate capability and high cycle life. This experiment demonstrates that cyano compounds as cathodes for aqueous aluminum batteries open a new research avenue for safer and more efficient aqueous storage systems.