Abstract: Enhanced methods for preparing activated carbons have been discovered. In order to form an activated carbon, a carbon precursor material is coated with a phosphorus based chemical solution and physically activated. An activated carbon may also be formed by coating a green carbon precursor with a chemical solution that chemically reacts with carbon, carbonizing the resulting material, and physically activating the material during at least a portion of the carbonizing step. An activated carbon may also be formed by milling a carbon material to a predetermined particle size, then activating the milled particles. In another enhancement, an activated carbon is formed by coating a carbon or carbon precursor with nanoparticles, carbonizing if the carbon is a carbon precursor, then catalytically activating in air and an inert gas, and physically activating in steam or carbon dioxide. An activated carbon may also be formed by physically activating a previously chemically activated carbon.

Abstract: 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.

Abstract: An asymmetric supercapacitor has a positive electrode having a current collector an active material selected from the group consisting of manganese dioxide, silver oxide, iron sulfide and mixtures thereof, a negative electrode having a carbonaceous active material carbon and optional current collector, an electrolyte, and a separator plate. In a preferred embodiment at least one of the electrodes has nanostructured/nanofibrous material and in a more preferred embodiment, both electrodes have nanostructured/nanfibrous material. The electrolyte can be liquid or solid although liquid electrolytes are preferred. The asymmetric supercapacitor has improved energy density by electrically coupling an electrode of high faradaic capacity such as one having manganese oxide (MnO2) with an electrode such as carbon that stores charge through charge separation at the electric double-layer. The asymmetric supercapacitor also improves power density by using high surface area nanostructured/nanofibrous electrode materials.