Polyimide-based covalent organic frameworks with dual redox-active centers as a high-performance anode for lithium-ion batteries

Organic materials have become emerging electrode materials for lithium-ion batteries due to their high capacity, sustainability and molecular tunability. However, their commercial application faces bottlenecks such as insufficient conductivity and potential dissolution in organic electrolytes. Here, a polyimide-based covalent organic framework (TA-NTCDA) containing dual-redox active sites was synthesized by using melamine and 1,4,5,8-naphthalenetetracarboxylic anhydride as monomers. The π-conjugated structure of TA-NTCDA not only accelerates charge transfer, but also inhibits its dissolution in organic electrolytes. The abundant carbonyl and triazine units in TA-NTCDA provide a large number of active sites for the deionization/intercalation of lithium ions, which can effectively increase the theoretical specific capacity. As the anode of lithium-ion batteries, TA-NTCDA demonstrated high capacity and long cycle stability, with a specific capacity of 1283 mAh·g⁻¹ after 250 cycles at a current density of 0.25 A·g⁻¹. Even at a high current density of 2.5 A·g⁻¹, the TA-NTCDA electrode still exhibited excellent stability. Its capacity reached a peak of 860 mAh·g⁻¹ after 300 cycles and was still able to maintain a high level of 634 mAh·g⁻¹ after 600 cycles. In addition, theoretical calculations revealed the applicability of TA-NTCDA as an anode material and the binding ability of different active sites to lithium ions. This study provides an effective strategy for the design of high-performance polyimide-based electrode materials.