A flower shaped MnO₂ have been synthesized using simple and low temperature procedure. Subsequently, an asymmetric supercapacitor is fabricated using MnO₂ and activated carbon as positive and negative electrode in aqueous electrolyte. The supercapacitor was measured at open windows 2.0 V showing energy density of 25.79 Wh/kg at power density of 100 W/kg. The supercapacitor stability was tested at 3 A/g and showing specific capacitance retention of 95% after 850 cycles.