The poor electronic and ionic conductivities of covalent organic frameworks (COFs) severely restrict the development of COF-based electrodes for practical rechargeable batteries, therefore inspiring more research interest from the direction of both material synthesis and technology. Herein, a dual-porous COF, USTB-6, with good crystallinity and rich redox-active sites is conceived and fabricated by the polymerization of 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino [2,3-a:2',3'-c]phenazine and 2,7-diaminopyrene-4,5,9,10-tetraone. In particular, the heterogeneous polymerization of the same starting materials in the presence of graphene affords uniformly dispersed COF nanosheets with a thickness of 8.3 nm on a conductive carbon substrate, effectively enhancing the electronic conductivity of the COF-based electrode. Such a graphene-supported USTB-6 nanosheets cathode when used in a lithium-ion battery exhibits a specific capacity of 285 mA h g-1 at a current density of 0.2 C and excellent rate performance with a prominent capacity of 188 mA h g-1 at 10 C. More importantly, a capacity of 170 mA h g-1 is retained by using the USTB-6 nanosheets cathode after 6000 cycles charge and discharge measurement at 5 C.
Keywords: cathodes; covalent organic frameworks; graphene; lithium organic batteries; nanosheets.
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