A Microporous Covalent-Organic Framework with Abundant Accessible Carbonyl Groups for Lithium-Ion Batteries

A key challenge faced by organic electrodes is how to promote the redox reactions of functional groups to achieve high specific capacity and rate performance. Here, we report a two-dimensional (2D) microporous covalent-organic framework (COF), poly(imide-benzoquinone), via in situ polymerization on graphene (PIBN-G) to function as a cathode material for lithium-ion batteries (LIBs). Such a structure favors charge transfer from graphene to PIBN and full access of both electrons and Li⁺ ions to the abundant redox-active carbonyl groups, which are essential for battery reactions. This enables large reversible specific capacities of 271.0 and 193.1 mAh g^-1 at 0.1 and 10 C, respectively, and retention of more than 86 % after 300 cycles. The discharging/charging process successively involves 8 Li⁺ and 2 Li⁺ in the carbonyl groups of the respective imide and quinone groups. The structural merits of PIBN-G will trigger more investigations into the designable and versatile COFs for electrochemistry.