Computational design of phenazine derivative molecules as redox-active electrolyte materials in alkaline aqueous organic flow batteries

Phenazine derivatives represent an important class of emerging redox-active organic electrolyte materials in aqueous flow batteries for sustainable energy storage applications. But when serving as the anolyte or catholyte, the working voltage is relatively low in comparison to their inorganic counterparts. Moreover, most of the reported phenazine-based electrolyte materials have insufficient water-solubility, which plague their application to aqueous flow battery systems. Here, we investigated the redox potentials and solvation free energies for phenazine derivatives containing various electron-donating or electron-withdrawing groups at different substitution positions by applying density functional theory calculations combined with a thermodynamic Born-Haber cycle. The calculation results are validated with experimental data. On the basis of our calculations, we identified several promising anolyte and catholyte candidates for alkaline aqueous organic flow batteries. The information obtained from this study can provide useful clues for designing high-performance redox-active electrolyte materials to promote the practical application of aqueous organic flow batteries.