Dissolution Inhibition via Intramolecular N···I Halogen Bond Enables High-Loading Zn-Organic Battery

The development of aqueous zinc-ion batteries faces persistent challenges in reconciling high mass-loading capabilities with extreme tolerance, particularly for organic cathodes prone to dissolution in aqueous electrolyte. Here, we present a halogen-bonded azo-based cathode material, 4,4'-azopyridine-iodide (AZPY-I), engineered through iodine-mediated molecular stabilization of pyridinic nitrogen sites. Analyses reveal that AZPY-I adopts a robust π-π conjugated framework stabilized by directional N···I halogen bonds, achieving ultralow solubility (<0.5 mg mL-1 in H2O) while introducing dual redox-active sites with six-electron transfer capability (N═N and I2 moieties). The Zn||AZPY-I cell delivers a near-theoretical capacity of 202 mAh g-1 with a high mass loading of 22.8 mg cm-2 at 0.5 A g-1, sustaining a 92% capacity retention over 150 cycles. At an ultrahigh current density (8 A g-1, ∼34.5 C), the cell demonstrates exceptional cyclability for 150,000 cycles with 0.00032% capacity decay per cycle. This work establishes halogen-bonded molecular engineering as a universal paradigm for designing dissolution-resistant organic electrodes, bridging molecular crystallography with practical battery metrics.