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

Abstract

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_TPDA-PMDA) with <b><i>kgm</i></b> topology consisting of dual active centers of <i>N</i>,<i>N</i>,<i>N</i>',<i>N</i>'-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA) and pyromellitic dianhydride (PMDA) ligands was successfully synthesized with high crystallinity and porosity. The COF_TPDA-PMDA possesses hierarchical micro-/mesoporous channels with the largest surface area (2669 m²/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_TPDA-PMDA@50%CNT which integrated high surface area and dual active center of COF_TPDA-PMDA 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.