An Organic Small Molecule Electrode with Intermolecular Intercalation and Synergistic Effects for High-Rate Alkali Metal-Ion Batteries

Designable molecular structures, unique ion-coordination charge storage mechanisms, and resource sustainability enable organic electrode materials to become potential candidates for alkali metal-ion batteries (AMIBs). Herein, integrating the excellent π–π stacking ability of Hexaazatriphenylene units and strong electron-withdrawing properties of cyano (C≡N) groups into one moleuce, a π-conjugated organic compound 1,4,5,8,9,11-Hexaazatrip henylenehexacarbonitrile (HAT-CN) is synthesized and systematically investigated as electrodes in Li/Na/K-ion batteries. Explored by mechanism characterizations and density functional theory calculations, HAT-CN can provide nine redox-active sites for Na/K-ions to intercalate/de-intercalate, among which six Na/K-ions are distributed evenly to both sides of conjugated skeletons through intermolecular intercalation and three Na/K-ions are stored with the synergistic effect of C≡N groups. Employing HAT-CN as electrodes, AMIBs are found to exhibit high reversible capacities, excellent rate capabilities, and stable cycle performances. After 100 cycles at the current density of 100 mA g⁻¹, Na-ion batteries present 415.6 mAh g⁻¹ with a capacity fading rate of 1.2% per cycle. Meanwhile, K-ion batteries maintain 345 mAh g⁻¹ with a coulombic efficiency ≈100%. Li-ion batteries display superlithiation performances with ultra-high reversible capacity. This work emphasizes the necessity of comprehensively studying the electrochemical performance of organic electrodes in different secondary battery systems and is conducive to maximizing electrode functionality. © 2024 Wiley-VCH GmbH.