Rational design of MXene/MWCNT/TOCNF film for flexible supercapacitor

Two-dimensional (2D) MXenes are widely acknowledged as highly adaptable materials for flexible supercapacitors due to their high electronic conductivity, tunable surface chemistry, structural adaptability, and excellent mechanical strength. However, pure MXene nanosheets have a tendency to stack together, which decreases the mechanical and electrochemical properties for flexible devices. Herein, inspired by the structure of modern architecture, MXene/MWCNT/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical-mediated oxidized cellulose nanofibers (TOCNFs) (MMT) composite film (MMT-X, the content of MWCNT and TOCNFs is X% of the total weight of the film) is manufactured using a simple vacuum filtration method. In MMT, two-dimensional (2D) MXene is severed as nanometer "bricks", one-dimensional (1D) TOCNFs is used as a nanometer "mortar" between MWCNTs and MXene based on synergistic electrostatic forces and hydrogen bonding to build a three-dimensional (3D) composite structures with excellent mechanical strength. The flexible MMT-8 film is used as a supercapacitor electrode with specific capacity 856 F cm-3. Furthermore, at a volume power density of 335.5 W L-1, the assembled flexible all-solid-state supercapacitor (ASSC) could provide a volumetric energy density of 11.64 Wh L-1 with good cycle stability.