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 (DAAQ)-1,3,5-triformylphloroglucinol (TFP) COF is synthesized on dialdehyde cellulose fibers (DACF) with hyperbranched polyamide-amine (HPAMAM) as a stabilizer. After carbonization, the COF is uniformly and stably supported on the conductive carbon fibers (CCF) for preparing composite paper electrode (CCF/HPAMAM/COF paper). The carbonized fibers provide mechanical support for 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 its porous structure. The CCF/HPAMAM/COF paper exhibits high volume specific capacitance (66.7 F cm-3at 0.5 mA cm-2), good rate capability (capacitance retention of 82% with 10 times current density), and long lifetime (charge-discharge stability of 93.7% after 10000 cycles). This work develops a carbonized paper-supported electrode with stable loading of COFs on carbonized fibers for new generation sustainable supercapacitors.