Free-standing Ni-microfiber-supported carbon nanotube aerogel hybrid electrodes in 3D for high-performance supercapacitors

Macroscopic Ni-microfiber-supported carbon nanotube aerogels (CNAGs) have been developed and demonstrate great potential as supercapacitor electrodes. The macroscopic carbon nanotubes (CNTs) are controllably prepared by a catalytic chemical vapour deposition method through CNT growth on a sinter-locked microfibrous structure (SMF) consisting of 5 vol% 8 μm Ni fibers. Polyimide is coated onto the CNTs rooted on the SMF-Ni by an impregnation/polymerization method and is subsequently carbonized by pyrolysis to create self-supporting CNAGs/SMF-Ni composite electrodes, wherein the Ni-fiber network serves as current collector and the CNTs grown on the Ni fiber act as nano conducting wires to link the charge-storage carbon aerogel (CAG) particles. This novel approach permits desirable large-area fabrication and provides a unique combination of high CNAG-loading (up to 71.0 wt%; CAG/CNT: 1.44 wt/wt), binder-free feature, excellent electrical conductivity, large surface area, macro-/meso-/micro-sized hierarchical porous structure and high permeability. A typical hybrid consisting of 68.5 wt% CNAG (CAG/CNT: 1.17 wt/wt) delivers not only a good capacitance (e.g., 359 F per gram CAG) at high rates but also excellent long-cycle life (5% loss after 300 cyclic voltammogram cycles and then almost unchanged through 1000 cycles).