An energy cable comprises at least one cable core comprising an electric conductor, a crosslinked electrically insulating layer, and particles of a zeolite system comprising at least a first zeolite and a second zeolite placed in the cable core. A method for extracting crosslinking by-products from a cross-linked electrically insulating layer of an energy cable core comprises manufacturing the energy cable core comprising particles of the above-said zeolite system, heating the energy cable core up to a temperature causing migration of the crosslinking by-products from the crosslinked electrically insulating layer, and placing a metal screen around the energy cable core.