Side-Chain Symmetry Breaking in Naphthalene Diimides Decouples High Concentration From Cycling Stability in Neutral Aqueous Organic Redox Flow Batteries

Neutral aqueous organic redox flow batteries (AORFBs) offer a promising pathway for transitioning renewables from supplementary to primary energy sources. However, their advancement is constrained by the limited long-term cycling stability and sluggish redox kinetics of materials under high-concentration conditions. Although introducing hydrophilic groups can mitigate these issues, highly symmetric molecular architectures often impose performance penalties. In this study, a series of asymmetrically modified naphthalene diimide derivatives were synthesized via a one-pot symmetry-breaking strategy, which diol-dex-NDI achieves a high solubility of 1.82 M. Density functional theory and Molecular dynamics simulations reveal that diol-dex-NDI preferentially adopts a dynamic antiparallel π–π stacking mode, enhancing thermodynamic stability while effectively suppressing molecular aggregation. In situ Raman spectroscopy uncovers hydration shell dynamics during electron transfer, showing a 35% reduction in desolvation energy barrier compared to dex-NDI. Furthermore, π–π and dipole interactions with the electrode enhance adsorption energy and accelerate electron transfer. This molecular design also strengthens the key C─N bond, as evidenced by increased bond dissociation energy, thereby intrinsically improving resistance to electrochemical degradation. Leveraging these advantages, 1.0 M (2 M e⁻) diol-dex-NDI/MiAcNH-TEMPO-based AORFB delivers stable performance over 620 cycles without notable capacity decay. This work highlights the potential of symmetry-breaking molecular engineering for practical AORFB applications.