Highly conductive, twistable and bendable polypyrrole-carbon nanotube fiber for efficient supercapacitor electrodes

Carbon nanotubes (CNTs) are a promising candidate for flexible and wearable electronic applications. Here, we report a conductive, twistable and bendable CNT composite fiber with core-shell structure for efficient supercapacitor electrode, where the CNT bundles are coated with a thin layer of polypyrrole (PPy) (denoted as PPy@CNT). The electrochemical properties of the fiber electrode depend on the content and distribution of the PPy. The PPy@CNT fiber exhibits a high specific capacitance of 350 F g(-1) and high stability in cyclic testing. The outstanding electrochemical performance originates from the high conductivity of the coreshell structured PPy@CNT composite, which makes charge transfer easily between PPy and CNTs. The PPy@CNT fiber is also stable under bending and twisting.