Design Strategy for Small-Molecule Organic Cathodes: Regulated Active Groups Enable High Capacity and Voltage in...

Organic materials demonstrate significant potential as electrodes for aqueous batteries, owing to their high theoretical capacity, structurally tunable frameworks, and sustainable material accessibility. Small-molecule organic electrode materials enable better active-site accessibility but remain challenged by the dissolution in aqueous electrolytes, which deteriorates cycling stability, and poor conductivity due to limited conjugation. Here, we designed an organic small-molecule cathode material (DPPZ-CN) featuring functional pyridine, pyrazine, and cyano groups. Its highly conjugated fused N-heteroaromatic structure provides strong intermolecular interactions and high reactivity, resulting in improved stability, capacity, and conductivity. The electron-withdrawing cyano group further modulates electron delocalization and molecular orbitals, enhancing electronic conductivity and operating voltage. Through combined theoretical and experimental studies, including operando synchrotron FT-IR, in situ Raman, ex situ XPS, and ¹H NMR, we demonstrate that DPPZ-CN facilitates efficient dual-cation storage (Al³⁺/H⁺), thereby reducing Al³⁺ cation repulsion and induced structural distortion. As a result, the Al//DPPZ-CN battery exhibits outstanding capacity, a well-defined voltage plateau, and an extended lifespan in organic aluminum batteries with aqueous and seawater electrolytes, highlighting its potential for operation in challenging environments.