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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.