Bipolar Covalent Organic Frameworks Crafting Core-Shell Heterostructured Cathode for High-Performance Lithium-Organic...

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 PF₆ ^- 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.