Electrodes derived from carbon fiber-reinforced cellulose nanofiber/multiwalled carbon nanotube hybrid aerogels for high-energy flexible asymmetric supercapacitors

Developing electrodes with excellent electrochemical and mechanical properties is the key to achieve state-of-the-art flexible asymmetric supercapacitors (ASCs). This work proposes a facile and scalable strategy to prepare high-performance flexible electrodes based on carbon fiber-reinforced cellulose nanofiber/multiwalled carbon nanotube-hybrid aerogels (CF-CNF/MWCNT-HAs). The three-dimensional (3-D) porous structure, excellent conductivity, binder-free nature, and high strength of the CF-CNF/MWCNT-HAs enable it to serve as a powerful platform for constructing flexible electrodes with outstanding capacitive performance. The as-prepared CF-CNF/MWCNT/MnO2 positive electrode and CF-CNF/MWCNT/active carbon (AC) negative electrode display remarkably high areal-specific capacitances (1745 and 1273 mF/cm2 at a current density of 1 mA/cm2, respectively). In addition, the carbon fiber-reinforced electrode also presented an excellent mechanical property with a maximum stress up to 27.9 MPa. The as-fabricated CF-CNF/MWCNT/MnO2//CF-CNF/MWCNT/AC flexible ASC device exhibits significant capacitance and energy density of 19.4 F/cm3 and 8.93 mWh/cm3, respectively. Additionally, this flexible ASC device can retain more than 96.7% of its capacitance after 3000 charge-discharge cycles. These results will enable us to fabricate flexible solid-state ASC devices from CF-CNF/MWCNT-HAs, and to expand its applications in the fields of portable and wearable electronics.