The carboxylic acid functionalized multi-walled carbon nanotubes/polyaniline nanotubes (PANI-NTs)/carboxylic acid functionalized single-walled carbon nanotubes electrodes for the flexible supercapacitors are fabricated by the layer-by-layer vacuum filtration. This strategy is aimed to assist powdery PANI-NTs to form a binder-free electrode, and meanwhile avoid sufficient contact between PANI-NTs and carbon nanotubes, ensuring abundant channels with a low tortuosity for enhanced electrolyte permeation and ion diffusion as well as large ion available surface area. Consequently, the assembled all-solid-state device achieves a high areal capacitance (258 mF cm−2 at current density of 0.5 mA cm−2), a superior energy density (3.82 m Wh cm−3 at a power density 33 mW cm−3) and favorable cycle stability (75.1% capacitance retention after 5000 cycles). Furthermore, the supercapacitor possesses outstanding flexibility and can be 180° bended up to 1000 times without loss of capacitance. Our works reveal that electrode structure design and fabrication procedures are also significant factors that greatly dominates electrochemical performance of supercapacitors.
