Covalent Organic Nanosheets with a Tunable Electronic Structure to Achieve Unprecedented Stability and High‐Performance in Sodium‐Ion Batteries

Abstract

Abstract This study develops a new type of fluorinated covalent organic nanosheets (CONs) as anode materials for sodium‐ion batteries by incorporating an electron‐withdrawing benzothiadiazole (BT) unit and F atom into the framework. These modifications lead to a reduced bandgap and electron density, generating strong permanent dipoles that increased Na + accessible sites within the self‐assembled solid‐state structure. To elucidate the effect of these electronic changes, the Na + storage performance of fluorinated D/A‐CON‐10‐F is compared to that of nonfluorinated D/A‐CON‐10. The reduced electron density in D/A‐CON‐10‐F weakens its interaction with Na + , yet enhances ion and charge carrier conductivities, leading to improved electrochemical performance. Notably, D/A‐CON‐10‐F exhibits a reversible discharge capacity of ≈637 mA h g −1 at 100 mA g −1 , maintaining structural stability over 5000 cycles with excellent rate capability. These results demonstrate that dipole engineering in CONs effectively enhances charge transport and long‐term stability, offering a promising strategy for next‐generation sodium‐ion battery anodes.