Imine-based covalent organic framework containing benzoquinone active units as a cathode material for lithium-ion batteries

Redox-active covalent organic frameworks (COFs) have received much attention as promising cathode materials for rechargeable metal-ion batteries. Desirable properties such as ordered nanopores, structural diversity and environmental friendliness make them potential substitutes for the conventional inorganic layered cathodes. However, the rational design of redox active sites within the molecular backbone is challenging and remains a lack of diversity. Here, we design an imine-based covalent organic framework containing multiple benzoquinone active units. The Li||COF cells show two redox pairs associated with the benzoquinone–dilithium benzenediolate transformation at the edges and vertices of DCBH-TABQ-COF. A remarkably high theoretical specific capacity of 379.0 mAh g⁻¹ is attained regarding all the carbonyl active sites. Despite these impressive features, DCBH-TABQ-COF merely achieves a specific capacity of 60 mAh g⁻¹ during the initial discharge and shows significant capacity decline at a high current density of 2000 mA g⁻¹. This electrochemical failure is attributed to the structural defects caused by imperfect Schiff base polycondensation.