Bipolar Covalent Organic Frameworks Crafting Core–Shell Heterostructured Cathode for High–Performance Lithium–Organic Batteries

ABSTRACT Covalent organic frameworks (COFs) with tunable molecular structures and ordered porous channels have emerged as promising cathode materials for lithium–organic batteries. However, their practical application is still hindered by low operating voltages, limited specific capacities, and sluggish charge transport kinetics. In this work, a new carbon nanotube@bipolar COF (CNT@COF) core–shell heterostructure cathode was rationally crafted through the synergistic integration of molecular and microstructural engineering. The robust 3D hybrid architecture features a conductive CNT core and COF shells enriched with p–/n–type nitrogen electroactive sites, enabling rapid electron/ion transport while maximizing electrochemical utilization. Consequently, the CNT@COF cathode exhibits a high reversible capacity of 226.5 mAh g ⁻¹ , outstanding rate capability (137 mAh g ⁻¹ at 5 A g ⁻¹ ) and long–term cycling stability (82.5% at 5 A g ⁻¹ over 5000 cycles), outperforming most previously reported COF–based organic cathodes. The charge storage mechanism is further revealed by ex situ X–ray photoelectron spectroscopy, operando Fourier transform infrared spectroscopy, and theoretical calculations, involving PF ₆ ⁻ anions interacting with C–N bonds during p–type oxidation and Li ⁺ cations binding to C = N bonds through n–type reduction. Moreover, the assembled symmetric batteries exhibit both high–energy and high–power densities and operate effectively even under low–temperature conditions.