Carbon-encapsulated NiO nanoparticle decorated single-walled carbon nanotube thin films for binderless flexible electrodes of supercapacitors

With the rapid development of flexible electronic devices, flexible supercapacitors with a high power density and long life are urgently required. The performance of a supercapacitor is highly reliant on its electrode materials. Nickel oxide is a promising electrode material because of its high capacity, but its poor conductivity poses a challenge for its use in high-performance energy storage devices. Here, we report a flexible single-walled carbon nanotube (SWCNT) film decorated with a high content of carbon-encapsulated Ni (CENi) nanoparticles prepared using a floating catalyst chemical vapor deposition technique. After air oxidation, carbon-encapsulated NiO nanoparticle decorated SWCNT (CENiO/SWCNT) films were obtained. When used as a binder-free flexible electrode, this material displayed unchanged specific capacitance after 500 bending cycles at an angle of 130°. Furthermore, a high specific capacitance of 1422 F g-1 and an excellent cycling stability (92% capacitance retention after 5000 cycles) were obtained, which can be ascribed to the good electrical conductivity and flexibility of the SWCNT scaffold as well as the high capacity of the firmly attached NiO nanoparticles in the hybrid electrode.