Separator-Built-in ANF/MXene Composite Film Electrodes by Vacuum Filtration for Mechanically Robust Stretchable Supercapacitors

Stretchable supercapacitors (SCs) have been widely acknowledged as promising energy storage solutions in the field of functional wearable and biomedical electronics. In this work, aramid nanofibers (ANFs) and MXene (Ti 3 C 2 T x ) were integrated into a mechanically robust Janus-structured composite film via a facile one-step vacuum-assisted filtration approach. Structurally, the ANF/MXene film electrodes featured a highly conductive MXene network on one side and a fibrous ANF-enriched surface on the other. This design integrated a built-in separator, synergistically combining high conductivity with mechanical strength. Results showed that at the optimal 3:8 ANF/MXene ratio, the composites electrode achieved 2247.2 S/m conductivity, 61.53 MPa tensile strength, and a large specific capacitance of 246 F/g (0.05 A/g). The as-assembled separator-free SC exhibited a specific capacitance of 32.6 F/g at 0.05 A/g and exceptional charge–discharge cycling stability demonstrated by 112.7% capacitance retention after 2000 cycles, which can be attributed to electrochemical activation effects. Additionally, the electrodes exhibited excellent flexibility and foldability. Using a prestraining-then-buckling approach, the symmetric SC became stretchable, enduring crumpling and restretching without degradation. The stretchable SC maintained a stable operation under 20 crumpling-stretching deformation cycles. This work provides a promising strategy for fabricating stretchable energy storage devices for wearable electronics.