An electrode comprises an electrically conductive substrate, a layer of energy accumulating redox polymer deposited onto the substrate, the redox polymer comprising a polymer metal complex with a substituted tetra-dentate Schiff's base selected from the group: poly-[Me(R, R′—Y)], wherein Me is a transition metal; Y is a bridge group binding the atoms of Nitrogen in the Schiff's base; R is an electron-donating substituent comprising a functional group (X)O—, —COO(X), where (X) is an alkali metal; R′ is Hydrogen or Halogen; and wherein the polymer metal complex has the following structure: The electrochemical capacitor comprises a case housing the above-described positive electrode and a negative electrode disposed inside the case, and an electrolyte filling the space between the electrodes.