A cathode current collector assembly assembled in a carbon cathode of a Hall-Héroult cell for the production of aluminium, the cathode current collector assembly comprising at least one collector bar of a highly electrically conductive metal that is located under the carbon cathode, the highly-electrically conductive metal having an electrical conductivity greater than that of steel, characterized in that • the or each collector bar of highly electrically conductive metal extends lengthwise and comprises a central part located under a central part of the carbon cathode, said central part of the highly electrically conductive metal collector bar having at least an upper outer surface of the highly conductive metal in direct electrical contact with the carbon cathode or in contact with the carbon cathode through an electrically conductive interface formed by an electrically conductive glue applied over and in contact with the surface of the highly electrically conductive metal collector bar and/or by an electrically conductive flexible foil or flexible sheet, said flexible foil or flexible sheet being made of a metal cloth, mesh or foam of copper, a copper alloy, nickel or a nickel alloy, or a graphite foil or fabric, or a combination thereof that is applied over the surface of the highly electrically conductive metal collector bar; • the or each collector bar of the highly electrically conductive metal comprises along its length one outer part or two outer parts located adjacent to and respectively on one side or on either side of said central part and a terminal end part or two terminal end parts extending outwardly respectively from the one or two outer parts, and • the cathode current collector assembly further comprising an external steel conductor bar of greater cross-sectional area than the highly electrically conductive metal collector bar, said terminal end part(s) and only said terminal end part or parts of the at least one collector bar of highly electrically conductive metal collector bar being each connected to the external steel conductor bar so as to electrically connect in series the highly-electrically conductive metal constituting the collector bar and the external steel conductor bar, each said steel conductor bar extending outwardly for connection to an external current supply. • the or each collector bar of highly electrically conductive metal extends lengthwise and comprises a central part located under a central part of the carbon cathode, said central part of the highly electrically conductive metal collector bar having at least an upper outer surface of the highly conductive metal in direct electrical contact with the carbon cathode or in contact with the carbon cathode through an electrically conductive interface formed by an electrically conductive glue applied over and in contact with the surface of the highly electrically conductive metal collector bar and/or by an electrically conductive flexible foil or flexible sheet, said flexible foil or flexible sheet being made of a metal cloth, mesh or foam of copper, a copper alloy, nickel or a nickel alloy, or a graphite foil or fabric, or a combination thereof that is applied over the surface of the highly electrically conductive metal collector bar; • the or each collector bar of the highly electrically conductive metal comprises along its length one outer part or two outer parts located adjacent to and respectively on one side or on either side of said central part and a terminal end part or two terminal end parts extending outwardly respectively from the one or two outer parts, and • the cathode current collector assembly further comprising an external steel conductor bar of greater cross-sectional area than the highly electrically conductive metal collector bar, said terminal end part(s) and only said terminal end part or parts of the at least one collector bar of highly electrically conductive metal collector bar being each connected to the external steel conductor bar so as to electrically connect in series the highly-electrically conductive metal constituting the collector bar and the external steel conductor bar, each said steel conductor bar extending outwardly for connection to an external current supply.