Covalent Organic Nanosheets as Effective Sodium-Ion Storage Materials

Herein, we study the structure-dependent energy storage performance of network polymers (covalent organic nanosheets, CONs) prepared by Stille cross-coupling under conventional reflux and solvothermal conditions, showing that the specific surface area and self-assembled morphology of CONs could be effectively controlled by a careful choice of the synthetic route and monomer combination. The Na-ion storage capacity of the above nanosheets could be increased by enhancing their charge-carrier conductivity via enforcement of polymer backbone planarity or by increasing their specific surface area while maintaining backbone constitution. Comparison of anodes fabricated using six CONs showed that the electrode based on CON-16 exhibited the best cycling performance and rate capability, retaining a reversible discharge capacity of ～250 mA h/g after 30 cycles at a current density of 100 mA/g