A novel covalent organic framework with high-density imine groups for lithium storage as anode material in lithium-ion batteries

A novel hexaaminobenzene-based triangular topology covalent organic framework (HAB-COF) was first synthesized and studied as an anode material in the lithium-ion batteries. Benefiting from its conjugated structure and high-density C=N groups designed in the skeleton, the electrons transport and insertion/extraction of metal ions in HAB-COF got effectively promoted. Remarkably, upon a capacity-increasing and/or activation process, the HAB-COF organic electrode delivered high reversible capacities and excellent cycle life with a specific capacity of 1255 mAh g−1 at 1 A g−1 after 1100 cycles. Based on the analysis of cycled electrodes at different cycles, a stepwise-deepen thirty-electron lithiation mechanism of the covalent organic framework was speculated involving C=N bonds and steadily activated aromatic C=C groups. This work proves the potential of structure-designed COFs as electrode materials for high-capacity lithium-ion batteries, as well as deepens the fundamental understanding of storage mechanism.Graphical abstractA novel covalent organic framework (HAB-COF) with high-density imine groups is synthesized and studied as an anode in the lithium-ion batteries. Upon a capacity-increasing process, the HAB-COF organic electrode delivers excellent cycle performance with a specific capacity of 1255 mAh g−1 at 1 A g−1 after 1100 cycles and even 1927 mAh g−1 at 0.1 A g−1. A thirty-electron lithiation mechanism involving C=N and aromatic C=C groups is proposed for the HAB-COF.