An Asymmetric Ultracapacitors Utilizing α-Co(OH)2/Co3O4 Flakes Assisted by Electrochemically Alternating Voltage

α-Co(OH)2/Co3O4 flakes were obtained through alternating voltage induced electrochemical methodology at room temperature. The as-prepared α-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 α-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.