Multidimensional Nanostructural Engineering of MXene-Based Composite Films for High-Performance Supercapacitors

Advanced two-dimensional (2D) MXenes have been extensively researched as electrode materials for flexible supercapacitors due to their excellent electronic performance and flexibility. Herein, a facile and effective approach is adopted to synthesize a polypyrrole@bacterial cellulose/MXene (PPy@BC/MXene) hybrid film through a plunge-freezing and vacuum-assisted filtration self-assembly strategy. We have constructed an ordered "building frame structure" with MXene as the "beam and slab" and polypyrrole@bacterial cellulose (PPy@BC) as the "pillar." Benefiting from this vertical bridge, rapid interlaminar electroconductivity, unimpeded ion diffusion channels, and sufficient reactivity, the synthesized PPy@BC/MXene-25% electrode has achieved a high specific capacitance of 807 F g–1 at 0.05 mA cm–2 and a capacitance retention of 97.51% after 10 000 cycles at 20 mA cm–2. Besides, PPy@BC/MXene-25% exhibits high strain at break (∼10.8%) and high tensile strength (∼310 MPa). Moreover, the asymmetric microsupercapacitor PPy@BC/MXene-25%//MXene is assembled with PPy@BC/MXene-25% as the anode, which presents an average capacity of 464 F g–1 at 0.05 mA cm–2. The specific energy density of the PPy@BC/MXene-25%//MXene capacitor has achieved 135.3 μWh cm–2 at a power density of 435.4 μW cm–2 at 0.5 mA cm–2. The novel approach exploits a new way to design conductive freestanding flexible electrodes with significantly enhanced electrochemical properties.