An electrochemical alternating voltage approach of producing NiCo double hydroxide (NiCoDH) layered ultrathin nanoflakes with large specific surface area (355.8 m2 g鈥?), remarkable specific capacitance and rate capability is presented. The obtained NiCoDH as anode for asymmetric supercapacitors shows excellent energy density of 17.5 Wh kg鈥? at high power density of 10.5 kW kg鈥? and cycling stability (91.2% after 10鈥?00 cycles).