High-performance hybrid supercapacitors based on self-supported 3D ultrathin porous quaternary Zn-Ni-Al-Co oxide nanosheets

Mixed transition metal oxides with hierarchical, porous structures, constructed from interconnected nano-building blocks, are considered promising positive electrodes for high-performance hybrid supercapacitors. Here we report our findings in design, fabrication, and characterization of 3D hierarchical, porous quaternary zinc-nickel-aluminum-cobalt oxide (ZNACO) architectures assembled from well aligned nanosheets grown directly on nickel foam using a facile and scalable chemical bath deposition process followed by calcination. When tested as a binder-free electrode in a 3-electrode configuration, the ZNACO display high specific capacity (839.2 C g(-1) at 1 A g(-1)) and outstanding rate capability (similar to 82% capacity retention from 1 A g(-1) to 20 A g(-1)), superior to those of binary-component NiCo2O4 and ZnCo2O4 as well as single-component Co3O4 electrode. More remarkably, a hybrid supercapacitor consisting of an as-fabricated ZNACO positive electrode and an activated carbon negative electrode exhibits a high energy density of 72.4 Wh kg(-1) at a power density of 533 W kg(-1) while maintaining excellent cycling stability (similar to 90% capacitance retention after 10,000 cycles at 10 A g(-1)), demonstrating a promising potential for development of high-performance hybrid supercapacitors. Further, the unique electrode architecture is also applicable to other electrochemical systems such as batteries, fuel cells, and membrane reactors. (C) 2016 Elsevier Ltd. All rights reserved.