Asymmetric supercapacitors comprise: a positive electrode comprising a current collector and a first active material selected from the group consisting of manganese dioxide, silver oxide, iron sulfide, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, and a combination comprising at least one of the foregoing active materials; a negative electrode comprising a carbonaceous active material; an aqueous electrolyte solution selected from the group consisting of aqueous solutions of hydroxides of alkali metals, aqueous solutions of carbonates of alkali metals, aqueous solutions of chlorides of alkali metals, aqueous solutions of sulfates of alkali metals, aqueous solutions of nitrates of alkali metals, and a combination comprising at least one of the foregoing aqueous solutions; and a separator plate. Alternatively, the electrolyte can be a non-aqueous ionic conducting electrolyte or a solid electrolyte.