Redox active covalent organic framework-based conductive nanofibers for flexible energy storage device. (January 2021) - Kong, Xueying
Abstract: Covalent organic frameworks (COFs) constitute a family of crystalline porous polymers that are being studied for electrochemical energy storage. However, their low electrical conductivity and poor processability have largely limited their electrochemical performances and practical applications. Here, we develop an interfacial synthesis method to grow few-layered 2D redox-active COFs (DAAQ-TFP COF) on the surface of carboxylated carbon nanotubes (c-CNTs) in order to fabricate core-shell c-CNT@COF nanofibers, for which the thickness and the morphology of the COF nanolayers can be finely controlled. When using the c-CNT@COFs as electrode material, the tailored nanostructure with high electrical conductivity allows efficient electron transfer, while the few-layered structure of the COF promotes fast electrolyte ion diffusion in the near-surface region, which results in an efficient utilization of the redox active sites in COF. More significantly, c-CNT@COFs with nanofibrous structure show good processability and can be assembled into freestanding and flexible nanopapers with the assistance of Cladophora cellulose. Given the good electrochemical performance and excellent flexibility, the nanopaper electrodes are assembled into flexible hybrid capacitors, showing high areal capacitance and extremely long lifetime. This study provides a new pathway for the development of next generation sustainable and flexible energy storage devices based on COFs and cellulose materials. Graphical abstract: Image 1 Highlights: Redox-active COF nanolayers with controlled morphology and thickness were fabricated on the surface of CNT. The obtained c-CNT@COF nanofibers showed high electrical conductivity and good processability. Interweaving the c-CNT@COF nanofibers with Cladophora cellulose and CNTs formed freestanding and flexible nanopapers. The nanopaper electrodes were assembled into flexible and foldable hybrid capacitors.