Supercapacitor, as an energy storage device, the capacitance is highly dependent on the properties of material, including its chemical composition and mesoscopic structure. In this study, we report a promising material, nickel-cobalt layered hydroxide, synthesized by simple hydrothermal co-precipitation. The NiCo hydroxides formed flacks first, and then self-assembled to flower-shape nanostructure. Due to its high surface area and the self-assembled structure, the material allows fast diffusion of ions (Ions have direct access to the material surface in the inner surfaces). Hence, the material was used to construct asymmetrical supercapacitor together with nitrogen-doped graphene aerogel. The energy-density of the supercapacitor reached 32 Wh/kg with the power density of 8027 W/kg. The supercapacitor also overcomes the general problem of short cycle-life with supercapacitor made of NiCo layered hydroxides.