Self-supported nickel cobalt carbonate hydroxide nanowires encapsulated cathodically expanded graphite paper for supercapacitor electrodes

The self-standing electrode materials with large surface area and high electronic conductivity have attracted intensive attention in energy storage devices. Herein, the expanded graphite paper (EGP) is fabricated via a controlled cathodic expansion in acetonitrile with tetrabutylammonium bromide at 10 V. The as-prepared EGP exhibits a three-dimensional porous structure with large specific surface area and high electronic conductivity, which is a favorable support for in situ growing nickel cobalt carbonate hydroxide (NiCo-CH) nanowires via a simple hydrothermal method. The as-prepared NiCo-CH@EGP composite achieves high areal capacity of 2.55 C cm−2 at 0.5 mA cm−2, and still remains 1.38 C cm−2 even at 60 mA cm−2. The assembled NiCo-CH@EGP//activated carbon asymmetric supercapacitor exhibits the maximum energy density of 0.30 mWh cm−2 at a power density of 0.92 mW cm−2, and a suitable cyclic stability with the capacity retention of 78.1 % after 10,000 cycles at 20 mA cm−2. The results indicate that the self-standing NiCo-CH@EGP is a potential electrode material for energy storage devices.