Curvature defect engineering towards a high-performance COF-based cathode in lithium-ion batteries

Covalent organic frameworks (COFs), a type of function-oriented porous material, show great potential in rechargeable batteries owing to well-defined ion channels and a flexible framework design. However, the active sites in COFs are almost impossible to fully utilize because of insufficient electron transport or ion diffusion. Here, a defect-rich COF@CNT cathode (RBT-COF@CNT-50) was designed using curvature defect engineering to enhance the electrochemical reaction kinetics. The synergistic effect of the defect-rich D-A framework with the CNT-interlaced network endows RBT-COF@CNT-50 with a higher electron conductivity of 2.65 × 10^-4 S m^-1. The emergence of additional defect decorated with polar functional groups in RBT-COF@CNT, induced by the curvature effects, contributes to faster ion diffusion. Consequently, RBT-COF@CNT-50 delivers a higher reaction rate of 1.22 × 10^-6 mol s^-1 m^-2. As expected, RBT-COF@CNT-50 reveals a high specific capacity of 302 mAh g^-1 at 0.1 A g^-1. It also exhibits excellent long-term cycling performance with 148 mA g^-1 at 2 A g^-1 for 2000 continuous cycles and 124 mA g^-1 with a capacity attenuation rate of 0.004% per cycle at 10 A g^-1, outperforming most reported COF/carbon composite cathodes. This work offers in-depth insights into the construction of high-performance COF-based cathodes by enhancing electrochemical reaction kinetics with curvature defect engineering.