Fe3O4 nanoparticles embedded in cellulose nanofibre/graphite carbon hybrid aerogels as advanced negative electrodes for flexible asymmetric supercapacitors

Fe3O4 is a negative electrode material with great development potential, but it remains a challenge for Fe3O4-based negative electrodes to attain excellent electrochemical performance and stability simultaneously with good flexibility, which limits their practical applications in high-performance flexible asymmetric supercapacitors (ASCs). In this study, a simple and scalable bottom-up strategy is presented to prepare three-dimensional (3D) porous CNF/MWCNT/GO-hybrid aerogels (HAs) based on one-dimensional (1D) cellulose nanofibers (CNFs) and multiwalled carbon nanotubes (MWCNTs) and two-dimensional (2D) graphene oxide (GO). After in situ embedding of Fe3O4 nanoparticles (∼200 nm) into the HA substrate, a high-performance flexible CNF/MWCNT/reduced-GO (RGO)/Fe3O4 electrode with a large capacitance of 1193 mF cm−2 and excellent rate capability as well as high durability has been synthesized. Moreover, when using this CNF/MWCNT/RGO/Fe3O4 as a negative electrode, the as-fabricated flexible ASC device exhibited a significant capacitance and energy density of 5.82 F cm−3 and 2.35 mW h cm−3, respectively. In addition, the flexible ASC device retained more than 94.7% of its initial capacitance after 5000 charge–discharge cycles. These results indicate that the proposed strategy can provide new opportunities for researchers to rationally design and prepare flexible ASC negative electrode materials with excellent capacitive properties, which will extend the application of such materials to the domain of portable and wearable electronics.