Realizing battery-like energy density with asymmetric supercapacitors achieved by using highly conductive three-dimensional graphene current collectors

We report a three-dimensional graphene network decorated with nickel nanoparticles as a current collector to achieve outstanding performance in Ni(OH)2-based supercapacitors with excellent energy density. A cost-efficient and single-step fabrication method creates nickel-particle decorated three-dimensional graphene networks (Ni–GNs) with an excellent electrical conductivity of 107 S m−1 and a surface area of 16.4 m2 g−1 that are superior to those of carbon alternatives and commercial 3D-Ni foam, respectively. The supercapacitor in which Ni(OH)2 active materials are deposited on Ni–GNs exhibited an outstanding capacitance value of 3179 F g−1 at 10 A g−1 in a three-electrode system and 90% of capacitance retention after 10 000 cycles. Furthermore, it showed an outstanding energy density of 197.5 W h kg−1 at a power density of 815.5 W kg−1 when tested in a two-electrode system. To the best of our knowledge, our device realized the world record value of energy density with a high rate capability and good cycle stability among Ni(OH)2-based supercapacitors. The excellent electrical properties of easily synthesized Ni–GNs as the ideal current collector clearly suggest a straightforward way to achieve great performance supercapacitors with both high energy density and power density.