An electrode core material has a substrate and at least one porous material layer diffusion-bonded to the substrate. The substrate is made of a metal foil processed into a three-dimensional structure which is substantially deformed from a major plane of the metal foil, preferably having bulge portions which protrude from at least one side of the metal foil, the bulge portions preferably having a curved, strip-shaped form between laterally spaced slits in the metal foil. The porous material layer is made of metal fine particles diffusion-bonded to each other, and the porous material layer has a three-dimensional structure which is substantially uniform in thickness and porosity. Methods are provided for producing the electrode core material by diffusion bonding the porous material layer to the substrate either before or after deforming the metal foil. The electrode core material may be used for the positive and/or negative electrode of an alkaline storage battery.