A complex hydroxide/metal Ni(OH)2@Ni core-shell electrode was developed for a high-performance and flexible pseudocapacitor. Compared to the conventional Ni(OH)2 electrode, the as-prepared amorphous Ni(OH)2@ three-dimensional (3D)Ni core-shell electrode shows a large specific capacitance of 2868 F g-1 at a scan rate of 1 mV s-1 and a good cycling stability (3% degradation after1,000 cycles) at a scan rate of 100 mV s-1. Furthermore, the high rate capability with a specific capacitance of 2454 F g-1 can be achieved at a charge/discharge current density of 5 A g-1. An amorphous Ni(OH)2@3D Ni-AC based asymmetric supercapacitor could be cycled reversibly in the high-voltage region between 0-1.3V and the specific capacitance of 92.8 F g-1 at 1 A g-1. This research demonstrates that introducing the metal core to conventional hydroxide supercapacitor electrodes could open up new opportunities for designing and developing High-Performance supercapacitors.