Symmetry-driven isotropic hydration suppresses degradation of anthraquinone positional isomers in aqueous organic flow batteries via dipole cancellation

Abstract Bimolecular degradation, via π-stacking, radical coupling, and desulfonation, severely limits the operational lifetime of anthraquinone-based anolytes in aqueous redox flow batteries. Molecular symmetry can promote protective, isotropic hydration around the electroactive core, yet this strategy remains underexplored. Herein, we establish a design principle: a symmetric, near-zero-dipole core nucleates a dense, uniformly bound hydration shell that sterically blocks bimolecular degradation. To test it, we synthesized anthraquinones with dipole moments from 25.4 to 0.0004 D. Only the perfectly symmetric 1,5-diaminoanthraquinone (15AQS) forms a complete, tightly packed hydration shell, stabilized by ~19 H-bonds per molecule, nearly double that of its analogue. Experimentally, 15AQS shows outstanding stability: capacity fade is just 0.00018% per cycle, 100× lower than benchmark 1,4- 2,6- and 2,7-derivatives, and delivers a peak power density of 342 mW·cm-2 at 0.5 M. Multimodal characterization confirms the hydration shell immobilizes –NH protons and shields the electron-rich C3 site from dimerization. Collectively, this study establishes a predictive, computationally tractable design rule, from core symmetry to isotropic hydration and then to degradation blockade, for enhancing the intrinsic longevity of organic energy-storage molecules.