Multiple Redox\nSite π‑Conjugated Materials\nfor Aqueous Aluminum–Organic Battery Cathodes

In the field of rechargeable aqueous aluminum batteries\n(AABs),\ncarbonyl- and imine-based organic materials have received much attention\ndue to their design flexibility. However, such materials usually face\nproblems such as low capacity and poor stability. For this reason,\na simple dehydration condensation method was employed to design a\nredox-active organic material (ROM)-BQPT (benzo[i]benzo[6,7]quinoxalino[2,3,9,10]phenanthrol[4,5-abc]phenazine-5,10,16,21-tetraone)\nof π-conjugated structure enriched with multiple C=O and C=N\ngroups. Due to the introduction of more redox-active sites, BQPT can\nprovide an extremely striking capacity of 396.4 mAh g<sup>–1</sup> at 0.2 A g<sup>–1</sup>. Additionally, the abundant π–π\nstructural interactions endowed BQPT with good structural stability\nand low solubility. In addition, further theoretical calculations\nconfirm that the reorganization of the electron cloud and the expansion\nof the π-conjugated ligand improve the redox kinetics of BQPT.\nCombined with ex situ characterizations, its reaction mechanism with\nAl(OTF)<sub>2</sub><sup>+</sup> was elucidated. This study provides\na significant reference for the design of new types of ROMs.