A method for producing a low oxygen content activated carbon material includes heating a natural, non-lignocellulosic carbon precursor in an inert or reducing atmosphere to form a first carbon material, mixing the first carbon material with an inorganic compound to form an aqueous mixture, heating the aqueous mixture in an inert or reducing atmosphere to incorporate the inorganic compound into the first carbon material, removing the inorganic compound from the first carbon material to produce a second carbon material, and heating the second carbon material in an inert or reducing atmosphere to form the low oxygen content activated carbon material. The activated carbon material is suitable to form improved carbon-based electrodes for use in high energy density devices.