Small-molecule organic compounds have emerged as attractive candidates for energy storage in lithium-ion batteries because of their sustainability and modularity. To develop generalizable design principles for organic electrode materials (OEMs), we investigated the correlation between electrochemical performance and addition of functional groups that promote synergistic hydrogen bonding and π−π stacking using a series of quinone-fused aza-phenazines (QAPs) with different hydrogen bonding donor/acceptor arrays. The QAP containing the most hydrogen bonding groups (3) exhibits the best performance with discharge capacities of 145 mAh g −1 at 2C and with 82% capacity retention over 1000 cycles. The performance of 3 is attributed to the strategically incorporated hydrogen bonding groups, which facilitate strong intermolecular interactions and a tightly packed 2D structure. The intermolecular interaction strength was evaluated using variable temperature 1D 1 H NMR and 2D 1 H− 1 H NOESY (nuclear Overhauser effect spectroscopy), offering a new strategy to help understand and predict the performance of OEMs with hydrogen bonding motifs.

Organic electrode materials have emerged as attractive alternatives to electrodes in lithium-ion batteries produced from toxic and unsustainably sourced transition metals. However, low-molecular-weight organic compounds still lack the cycling stability and high-rate capability found in transition-metal electrodes. Herein, we report S-rich thiazyl moieties as a new design feature for small-molecule organic electrode materials. Our findings suggest that S-rich thiazyl moieties engender strong intermolecular interactions that contribute to the insolubility and fast charging of low-molecular-weight quinones. This is demonstrated by the contrasting performance of three isomorphic bisthiazolyl quinones in the solid state: the quinone with the strongest intermolecular interactions can be cycled at a high rate of 10 C for 400 cycles with a 94% capacity retention, while those with weak intermolecular interactions suffer from dissolution and low cycling stabilities (<20 cycles). Our study reveals that S-rich thiazyl moieties may be used to design low-molecular-weight organic electrode materials to achieve long cycle life and fast electrode kinetics.

This study demonstrates the viability of the thiolate/disulfide redox couple in AZIB applications, and provides an in-depth study on the electrochemical mechanism of Zn-thiolates electrode materials.

Organic electrode materials (OEMs) provide sustainable alternatives to conventional electrode materials based on transition metals. However, the application of OEMs in lithium-ion and redox flow batteries requires either low or high solubility. Currently, the identification of new OEM candidates relies on chemical intuition and trial-and-error experimental testing, which is costly and time intensive. Herein, we develop a simple empirical model that predicts the solubility of anthraquinones based on functional group identity and substitution pattern. Within this statistical scaffold, a training set of 18 anthraquinone derivatives allows us to predict the solubility of 808 quinones. Internal and external validations show that our model can predict the solubility of anthraquinones in battery electrolytes within log S ± 0.7, which is a much higher accuracy than existing solubility models. As a demonstration of the utility of our approach, we identified several new anthraquinones with low solubilities and successfully demonstrated their utility experimentally in Li-organic cells.

Small-molecule organic compounds have emerged as attractive candidates for energy storage in lithium-ion batteries due to their sustainability and modularity. To develop generalizable design principles for organic electrode materials (OEMs), we investigated the correlation between electrochemical performance and addition of functional groups that promote synergistic hydrogen bonding and π-π stacking using a series of quinone-fused aza-phenazines (QAPs) with different hydrogen bonding donor/acceptor arrays. The QAP containing the most hydrogen bonding groups (<b>3</b>) exhibits the best performance with discharge capacities of 145 mAh g^-1 at 2C with 82% capacity retention over 1000 cycles. The performance of <b>3</b> is attributed to the strategically incorporated -OH and -NH₂ groups, which facilitate strong intermolecular interactions and a tightly packed 2D structure. The intermolecular interaction strength was evaluated using variable temperature 1D ¹H NMR and 2D ¹H-¹H NOESY, offering a new strategy to help understand and predict the performance of OEMs with hydrogen bonding motifs.