Highly Crystalline Polyimide Covalent Organic Framework as Dual-Active-Center Cathode for High-Performance Lithium-Ion Batteries.

Polyimide covalent organic framework (PI-COF) materials that can realize intrinsic redox reactions by changing the charge state of their electroactive sites are considered as emerging electrode materials for rechargeable devices. However, the highly crystalline PI-COFs with hierarchical porosity are less reported due to the rapid reaction between monomers and the poor reversibility of the polyimidization reaction. Here, we developed a water-assistant synthetic strategy to adjust the reaction rate of polyimidization, and PI-COF (COF) with topology consisting of dual active centers of ,,','-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA) and pyromellitic dianhydride (PMDA) ligands was successfully synthesized with high crystallinity and porosity. The COF possesses hierarchical micro-/mesoporous channels with the largest surface area (2669 m/g) in PI-COFs, which can promote the Li ions and bulky bis(trifluoromethanesulfonyl)imide (TFSI) ions in organic electrolyte to sufficiently interact with the dual active sites on COF skeleton to increase the specific capacity of cathode materials. As a cathode material for lithium-ion batteries, COF@50%CNT which integrated high surface area and dual active center of COF with carbon nanotubes via π-π interactions gave a high initial charge capacity of 233 mAh/g (0.5 A/g) and maintains at 80 mAh/g even at a high current density of 5.0 A/g after 1800 cycles.