Multiple Redox Site π-Conjugated Materials for Aqueous Aluminum–Organic Battery Cathodes

In the field of rechargeable aqueous aluminum batteries (AABs), carbonyl- and imine-based organic materials have received much attention due to their design flexibility. However, such materials usually face problems such as low capacity and poor stability. For this reason, a simple dehydration condensation method was employed to design a redox-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) of π-conjugated structure enriched with multiple C=O and C=N groups. Due to the introduction of more redox-active sites, BQPT can provide an extremely striking capacity of 396.4 mAh g–1 at 0.2 A g–1. Additionally, the abundant π–π structural interactions endowed BQPT with good structural stability and low solubility. In addition, further theoretical calculations confirm that the reorganization of the electron cloud and the expansion of the π-conjugated ligand improve the redox kinetics of BQPT. Combined with ex situ characterizations, its reaction mechanism with Al(OTF)2+ was elucidated. This study provides a significant reference for the design of new types of ROMs.