Mechanistic study demonstrates that symmetric dipole cancellation in anthraquinones enables protective isotropic hydration, highlighting a design pathway for stable aqueous flow batteries.
Key Points
To determine whether molecular symmetry and dipole cancellation in anthraquinone positional isomers can drive protective isotropic hydration shells that prevent bimolecular degradation.
Synthesized anthraquinone derivatives exhibiting molecular dipole moments ranging from 25.4 D down to 0.0004 D.
Evaluated battery cycling performance, capacity fade rate, and peak power density at 0.5 M concentration in an aqueous flow battery format.
Conducted multimodal characterization to evaluate hydration shell structure, hydrogen bonding network size, and steric protection of reactive sites.
The symmetric isomer 1,5-diaminoanthraquinone (15AQS) formed a dense, isotropic hydration shell stabilized by approximately 19 hydrogen bonds per molecule.
15AQS exhibited a capacity fade rate of 0.00018% per cycle, which was 100-fold lower than that observed for 1,4-, 2,6-, and 2,7-derivatives.
Aqueous flow cells using 15AQS delivered a peak power density of 342 mW·cm⁻² at 0.5 M by sterically shielding the electron-rich C3 position from dimerization.