Self-assembled polypyrrole nanotubes/MoS2 quantum dots for high performance solid state flexible symmetric supercapacitors

A new kind of chitosan–polypyrrole nanotube/molybdenum disulphide (CS–PNT/MoS2) nanocomposite is fabricated for the first time via a facile two-step in situ chemical polymerization and hydrothermal method, and successfully applied in flexible charge storage supercapacitor (SC) devices. The CS–PNT/MoS2 nanocomposite represents a good SC electrode material by inheriting the properties of good electrical conductivity of MoS2 and enhanced pseudocapacitive activity of polypyrrole nanotubes (PNTs). The incorporation of chitosan (CS) increases the cycling stability of the CS–PNT/MoS2 nanocomposite by reducing the aggregation of MoS2 quantum dots and enhancing the surface area and porous structure of the nanocomposite, which facilitates the diffusion of the solvent and faradaic process. The CS–PNT/MoS2 nanocomposite exhibits a highest specific capacity (Csp) of 759 C g−1 and a solid state flexible symmetric supercapacitor (SSC) was assembled using CS–PNTs/MoS2, which achieved a high-power density of 7680 W kg−1 at an energy density of 32.12 W h kg−1 and also good cycling stability with a capacity retention of 91.2% after 10 000 cycles at 10 A g−1. Remarkably, the SSC device showed enhanced flexibility and stability and can retain up to 97% of its initial capacity under various bending positions, clearly suggesting that the fabricated solid-state SSC device is exceptionally flexible and can be deformed without compromising its structural integrity and energy storage ability. These findings suggest that CS–PNTs/MoS2 represents a promising electrode material for flexible supercapacitors.