In this work, we have successfully synthesized MgNiO2 using a sol-gel wet chemical synthesis technique named MNO - 3. Electrochemical measurements in the presence of aqueous 1 M Li2SO4 electrolyte indicate that MNO - 3 samples exhibit a capacitance value of about 30 F/g and an energy density of about 20 Wh/kg. Subsequently, in the experiment involving aqueous 0.5 M Na2SO4 electrolyte system, it has been found that the capacitance for MNO - 3 sample is about 34 F/g and the energy density is about 23 Wh/kg for MNO - 3 sample. Finally, in the presence of aqueous-based 1 M Mg(ClO4)(2) electrolyte, MNO - 3 sample is found to exhibit a capacitance of about 26 F/g and an energy density of about 17 Wh/kg, respectively. In all three electrolyte systems, the MNO - 3 sample exhibit a long cycle capacitance retention of greater than 85% for 1000 charge-discharge cycles.