Co3O4 mesoporous nanostructure supported by Ni foam as high-performance supercapacitor electrodes

In various energy conversion and storage devices, supercapacitors have been extensively used due to their high power densities, fast delivery rates, and exceptionally long cycle lives. However, the low specific capacitances and low energy densities of supercapacitors largely hinder widespread applications in large-scale energy conversion and storage systems. To improve the specific capacitances of the supercapacitors, the surface areas of the electrode materials should be made as large as possible to allow the capturing and releasing of particles (such as ions, molecules, or electric charges). Here in this work, we demonstrate an efficient approach to the large-scale production of Co3O4 mesoporous nanostructure supported by Ni foam via a simple hydrothermal synthesis followed by ambient annealing at 300 ℃ for 4 h. The designed and fabricated Co3O4 mesoporous nanostructures directly serve as binder- and conductive-agent-free electrodes for supercapacitors, which thus provide more chemical reaction sites, shorten the migration paths for electrons and ions, and improve the electrical conductivity. By taking advantage of the structural features and excellent electronic conductivity, the Co3O4 exhibits the ultrahigh specific capacitances (1.87 Fcm-2 (936 Fg-1) and 1.80 Fcm-2 (907 Fg-1) at current densities of 2.5 mAcm-2 and 5.5 mAcm-2, respectively), high rate capacitances (48.37% of the capacitance can be retained when the current density increases from 2.5 mAcm-2 to 100 mAcm-2) and excellent cycling stability (92.3% of the capacitance can be retained after 4000 charge/discharge cycles at a current density of 10 mAcm-2). The nanostructuring approach and utilizing a binder- and conductive-agent-free electrode can be readily extended to other electrochromic compounds of high-performance energy storage devices.