Carbonized paper-supported electrode with covalent organic framework layers on carbonized cellulose fibers for supercapacitor application

As a class of crystalline porous polymers, covalent organic frameworks (COFs) have shown great application potential in electrochemical energy storage due to their high specific surface area, porous structure, and multiple redox-active sites. However, there are some challenges for practical application of COFs, such as low electrical conductivity, easy stacking, weak mechanical strength, and poor processability. In this study, 2,6-diaminoanthraquinone-1,3,5-triformylphloroglucinol COF is synthesized on dialdehyde cellulose fibers with hyperbranched polyamide-amine (HPAMAM) as a stabilizer. After carbonization, the COF is uniformly and stably supported on the conductive carbon fibers (CCFs) for preparing composite paper electrode (CCF-HPAMAM-COF paper). The carbonized fibers provide mechanical support for the COF and improve the electron transfer efficiency. While the COF layers shorten the ion diffusion path for high utilization of redox-active sites due to their porous structure, the CCF-HPAMAM-COF paper exhibits high volume-specific capacitance (66.7 F/cm3 at 0.5 mA/cm2), good rate capability (capacitance retention of 82% with 10 times current density), and a long lifetime (a charge-discharge stability of 93.7% after 10,000 cycles). This work develops a carbonized paper-supported electrode with stable loading of COFs on carbonized fibers for new generation sustainable supercapacitors.