Coaxial fabrication of Ni-Co layered double hydroxide into 3D carbon nanotube networks for high-performance flexible fiber supercapacitors

Asymmetric fiber-shaped supercapacitors (FSCs), especially those using pseudocapacitive materials, have been considered one of the most promising candidates for high-performance electrochemical devices. Herein, we design a flexible, asymmetric FSC consisting of carbon fiber (CF) as the substrate, multiple and alternate Ni-Co layered double hydroxide/mono-dispersed carbon nanotube (CNT) coaxial layers ([Ni-Co LDH-x/CNT-y]@CF) as the positive electrode materials and tremella-derived activated carbon@CF (TDC-z@CF) as the negative electrode material. The 3D Ni-Co LDH/mono-dispersed CNT networks enable the high mass loading of active materials, fast electron transfer, efficient ion diffusion, and mechanical stress release. TDC-z possesses large surface areas with hierarchical porous structures, thus demonstrating high capacitive performance. Based on that, the resulting FSC achieves a remarkable energy density of 26.20 Wh kg⁻¹, a power density of 7569.23 W kg⁻¹, and a superior cycling stability of 112.5% over 5000 cycles at a current density of 5 A g⁻¹. Several supercapacitors connected in series can also drive a portable LED device for over 10 min. Furthermore, the assembled device also exhibits excellent mechanical stability under various deformation conditions. These appealing properties make our FSCs an attractive candidate for powering wearable and flexible electronic devices.