Ultrahigh-power all binder-free hybrid supercapacitors based on single-crystal hexagonal nanorods of molecular sieve VSB-5 hierarchical electrodes

Abstract

BackgroundMolecular sieve Versailles Santa Barbara-5 (VSB-5) is a highly porous nanomaterial for electrochemical supercapacitor. MethodsA facile hydrothermal method is used to directly synthesize VSB-5 nanorods onto the Nickel Foam (NF). Significant findingsIn this work, one-dimensional single-crystal hydrogen nickel phosphate hydroxide hydrate (Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]·12H2O, also denotes as VSB-5, hexagonal nanorods arrays are successfully synthesized on NF via a hydrothermal method, and applied them as positive electrodes for hybrid supercapacitor (HSC). The resultant open framework of VSB-5 with unique nanochannels provides the synchronous advantages of a large surface area with numerous active sites for enhancing faradic redox reactions and abundant pathways for promoting electrolyte ions diffusion, thus leading to excellent energy storage behavior. Furthermore, the HSC is fabricated by paring the direct growth of carbon nanotubes (CNTs) on NF as the electrical-double-layer-capacitor negative electrode. Both the VSB-5/NF and CNTs/NF electrodes are binder-free hierarchical structures, owning the lowest interfacial resistivities between active materials and current collects, avoiding the aggregation issues to allow the facile diffusion of electrolyte for maximally utilizing the surface area. The resultant all binder-free VSB-5/NF//CNTs/NF HSC shows remarkable electrochemical performance, which delivers a maximum energy density of 46.9 W h kg−1 at a power density of 1225 W kg−1 with excellent capacity retention of 98.18% after 10,000 cycles.