Abstract— Poly (3, 4-ethylenedioxythiophene) (PEDOT)– Manganese Oxide (MnO₂) composite electrodes were made to assemble a symmetrical solid-state supercapacitor. The electrode was prepared by different synthetic routes; the first one was obtained by dipping a pulsed polymerized PEDOT film inside a solution mixture of potassium permanganate KMnO₄ and manganese sulfate MnSO₄, and the second one was obtained by dipping the PEDOT film inside KMnO₄, which resulted in a thinner MnO₂ layer, and thus better results. The presence of MnO₂ was confirmed by the symmetrical stretching vibration of the MnO₆ groups and the peak corresponding to Lithium Birenessite, with reference to the relevant literature. The optimum MnO₂ thickness was reached by soaking the PEDOT electrode in the MnO₂ solution for 10 minutes, reaching a 40°C temperature, which corresponded to the thinnest MnO₂ layer. The optimum PEDOT thickness was achieved by adjusting the number of cycles to 20K, resulting in the thickest PEDOT film with the highest conductivity. The supercapacitor exhibited a maximum capacitance of 122.08 mF cm^-2 at 10 mVs^-1. The ultimate specific energy and power values were 26.19 Wh kg^-1 and 6.09 kW kg^-1. The supercapacitor device showed a stable electrochemical behavior when subjected to a charge-discharge life test of 1000 consecutive cycles with an average Coulomb efficiency of 94.6%.