alpha-Co(OH)(2)/Co3O4 flakes were obtained through alternating voltage induced electrochemical methodology at room temperature. The as-prepared alpha-Co(OH)(2)/Co3O4 flakes displayed a high specific capacitance of 583 F g(-1) at a current density of 1 A g(-1). An asymmetric supercapacitor is further fabricated with the alpha-Co(OH)(2)/Co3O4 nanocomposite as the anode and activated carbon as the cathode in 2 M aqueous KOH solution as electrolyte. This asymmetric capacitor exhibited a maximum energy density of 22.4 Wh kg(-1) at power density of 290 W kg(-1). Moreover, the asymmetric supercapacitor showed an excellent cycling stability without obvious specific capacitance loss after 2000 cycles at a current density of 1 A g(-1). (C) 2014 Elsevier Ltd. All rights reserved.