Cathode current collector and connector assembly for aluminum electrolysis cell

Abstract

The present invention relates to a cathode current collector and connector assembly and a kit of parts for manufacturing a cathode current collector and an aluminum electrolysis cell.

Description

[Technical Field]

[0001] The present invention relates to a cathode current collector and connector assembly, a parts kit for manufacturing the cathode current collector, and an aluminum electrolysis cell comprising the cathode current collector and connector assembly. [Background technology]

[0002] Aluminum is produced by the Hall-Heoldt process, which involves dissolving aluminum oxide in a cryolite-based electrolyte and electrolyzing it at temperatures up to 1000 °C. A typical Hall-Heoldt cell consists of a steel shell, an insulating layer of refractory material, and a carbon cathode that holds the liquid metal. The cathode consists of multiple cathode blocks with collector rods embedded in the bottom to extract the current.

[0003] Several patent publications propose different approaches to minimizing the voltage drop from the liquid metal to the tip of the collector rod. WO 2008 / 062318 discloses the use of a highly conductive material to complement existing steel collector rods. WO 02 / 42525, WO 01 / 63014, WO 01 / 27353, WO 2004 / 031452, and WO 2005 / 098093 describe solutions using copper inserts within the collector rod. U.S. Patent 4,795,540 employs a structure that divides the cathode and collector rod into sections. WO 2001 / 27353 and WO 2001 / 063014 use highly conductive materials within the collector rod. U.S. Patent 2006 / 0151333 involves using collector rods with different electrical conductivities. WO 2007 / 118510 proposes a method for modifying the current distribution on the cathode surface by increasing the cross-sectional area of ​​the collector rods as they move toward the center of the cell. US Pat. Nos. 5,976,333 and 6,231,745 propose the use of copper inserts within steel collector rods. EP 2133446 A1 describes a method for adjusting the cathode surface geometry by modifying the cathode block arrangement to stabilize the metal pad surface waves and thereby minimize the ACD (anode-to-cathode distance). WO 2011 / 148347 describes a carbon cathode for an aluminum production cell that includes a highly electrically conductive insert sealed within the carbon cathode. These inserts modify the conductivity of the cathode body but are not used for current collection or extraction by the collector rods. The electrical conductivity of molten cryolite is very low, and the occurrence of magneto-hydrodynamic instabilities causes waves at the metal-bath (metal-cryolite electrolyte) interface, preventing a significant reduction in the ACD. The presence of waves reduces the current efficiency of the process, making it impossible to reduce energy consumption below a critical value. On average, in the aluminum industry, the current density is set so that the voltage drop across the ACD is minimal at 0.3 V / cm. Since the ACD is 3 cm to 5 cm, the voltage drop across the ACD is typically 1.0 V to 1.5 V. The magnetic field within the liquid metal is generated by the current flowing through the external busbar and the internal current.The internal local current density within the liquid metal is primarily determined by the cathode geometry and its local electrical conductivity. The magnetic field and current density generate a Lorentz force field, which shapes the contours of the metal surface. The metal velocity field defines the basic environment for the stability of the magnetohydrodynamic cell. Cell stability can be expressed as the ability to reduce ACD without generating unstable waves on the surface of the metal pad. The level of stability depends on the current density and magnetic field induction, but also on the liquid metal pool geometry. The pool geometry depends on the cathode surface and step geometry. Conventional solutions can meet the required magnetohydrodynamic conditions at a certain level and achieve good cell stability (low ACD), but solutions using copper inserts often require complex processing steps.

[0004] Therefore, in recent years, there has been a trend to replace steel collector rods with copper inserts with pure copper collector rods. Copper collector rods typically have a central section that serves as a support beneath the central section of the carbon cathode, usually directly positioned in the cathode slot or through-hole. At least the upper outer surface of this central section of the copper collector rod is in direct electrical contact with the carbon cathode or is in contact with the carbon cathode via an electrically conductive interface formed of an electrically conductive adhesive and / or an electrically conductive flexible film or sheet. The copper collector rod is comprised of one or two outer sections located adjacent to one or both sides of the central section and a terminal end or groups of terminal ends extending outward from the outer sections. The terminal ends of these copper collector rods are each electrically connected in series to a steel conductor rod with a larger cross-sectional area than the highly conductive collector rod, which extends outward for connection to an external power bus bar.

[0005] In this known arrangement, the terminal end of the highly electrically conductive metal rod is joined to the steel conductor rod by welding, electrically conductive adhesive, or by applying mechanical pressure, such as clamps, to form a transition joint that secures the highly electrically conductive metal rod and the steel conductor rod together. Alternatively, the fixed end is threadedly connected. The transition joint formed by the steel rod extends outward for connection to a bus rod network external to the cell, and the outward-extending steel rod end has an enlarged cross-sectional area to reduce voltage drop and maintain thermal balance of the cell. This known arrangement of forming the transition joint with the steel rod is partially satisfactory in that it provides sufficient heat dissipation with a small overvoltage penalty. However, the copper / steel joint is complex and increases manufacturing costs, and these copper / steel joints can deteriorate over time, causing poor contact. Furthermore, it has been found that there is a high risk of such connections failing, resulting in disconnections, high voltage drops, and energy losses, which can have a significant impact on cell performance.

[0006] Therefore, WO 2018 / 019888 A1 proposes simplifying the collector rod assembly by using a copper rod integrally molded from the inside of the carbon cathode to the outside of the cell, connecting it where a steel conductor element would traditionally be located. While eliminating the steel conductor element provides a degree of simplification, it requires adjusting the design of the copper rod at the terminal end or implementing additional connecting elements, such as copper or aluminum flex, to reduce heat flux to avoid freezing of the cryolite. Because implementing these design adjustments is laborious and costly, there remains a need for improvements in simple and efficient designs for current transfer elements. Summary of the Invention [Problem to be solved by the invention]

[0007] It is therefore an object of the present invention to provide a cathode current collector and connector assembly for an aluminium electrolysis cell which has higher performance, is more reliable, is more cost-effective and allows electrolysis with permanently low contact resistance and low voltage drop without the risk of cryolite freezing during operation of the electrolysis cell. [Means for solving the problem]

[0008] The above problems are solved by a cathode current collector and connector assembly for an aluminum electrolysis cell. The assembly comprises: a) a copper or copper alloy current collector system having an optional protective steel coating covering at least a portion of the current collector system; b) a carbide cathode having a groove for receiving a first portion of a current collector system; c) a steel conductor element having a recess for receiving a second portion of the current collector system; A first portion of the current collector system is disposed in the groove of the carbonaceous cathode, and a second portion of the current collector system is disposed in the recess of the steel conductor element, and the second portion of the current collector system is in at least partial direct contact with the steel conductor element.

[0009] The cathode current collector and connector current collector assembly comprises a carbonaceous cathode having a groove formed in one of its surfaces, in which a current collector system is at least partially disposed. The assembly further comprises a steel conductor element to which a terminal end of the current collection system (e.g., in the form of a collector rod) is electrically connected. The steel conductor element is connected to an external current supply bus rod for extracting current outside the cell. The conductor element preferably has a recess within which a second portion of the current collector system is at least partially disposed. Electrical current flows from the carbonaceous cathode through the copper rod and the steel conductor element to the external current supply bus rod, which conducts the current to the next cell. When both the collector element and the conductor element are rod-shaped, the conductor rod is configured to have a larger cross-sectional area than the collector rod, thereby further limiting heat flow from the cell and preventing freezing of the cryolite.

[0010] The grooves and corresponding ("negative electrode") current collector systems can have different shapes. Typically, the current collector systems are rod-shaped, particularly rectangular rod-shaped, although oval or round shapes are also possible. Preferably, the carbonaceous cathode has a rectangular shape, and the current collector systems (preferably rectangular rod-shaped) are disposed in grooves extending along the longitudinal surface of the carbonaceous cathode.

[0011] The current collector system and / or the steel conductor element may consist of one or more elements, in particular bar-shaped elements, particularly preferably rectangular bar-shaped elements.

[0012] Preferably, the current collector system consists of at least two longitudinal rectangular bar-shaped elements spaced apart from each other by a thermal expansion gap or insulating material.

[0013] In the present invention, "carbonaceous" refers to all types of materials based on anthracite and / or graphite and / or coke, whether these cathodes are calcined or graphitized or not.

[0014] When the second part of the current collector system is placed in a recess in the steel conductor element and is in at least partial direct contact with the steel conductor element, the inventors have observed that after heating an electrolytic cell equipped with the implemented current collector system, a reliable connection is formed between the current collector system and the steel conductor element.

[0015] Due to the high temperatures during heating and electrolysis, the second portion (e.g., rod-shaped) of the collector element, located in the recess, expands and presses against the steel conductor element. Without being bound by this theory, the inventors hypothesize that the pressure from heating and expansion initiates a diffusion process at the direct copper-steel interface, forming a stable, permanent material connection between the copper and steel with very low contact resistance. This thermally compatible connection is reliable and relatively easy to achieve. Furthermore, the use of a steel conductor element reduces heat flow from the cell, ensuring cell stability and preventing cryolite freezing.

[0016] The recess in the steel rod is preferably formed in such a way that it prevents the copper current collector system from moving in two or more, more preferably three or more, even more preferably four or more, or in four or more of six of the five spatial directions (Y1, Y2, X1, X2, Z1, Z2 shown in Figure 1) under normal conditions in accordance with DIN 1341, when the second part of the copper current collector system is located in the recess in the steel conducting element.

[0017] Preferably, the recess in the steel conductor element (e.g. rod-shaped) is formed in such a way that under operating conditions in the Hall-Heorold process, the recess prevents movement of the second part of the current collector system in one or more additional spatial directions compared to normal conditions.

[0018] Preferably, the recess in the steel rod is shaped to prevent movement of the second part of the current collection system by friction and / or material compatibility.

[0019] In particularly preferred embodiments, the recess has the shape of a pocket, preventing movement in four (open pocket) or five (completely surrounding pocket) of the six spatial directions. Since the pressure increases as the movement restriction increases, such embodiments enhance the above effect, resulting in tight friction and material conformity. The beneficial effect is maximized when the recess is a pocket that completely surrounds the steel rod.

[0020] To fix the copper current collector system in place, the steel conductor element can be made up of several sub-elements. For example, the pocket can be formed from two half-sections that combine to enclose the second part of the current collector system. Another option is to form a pocket that completely blocks movement in all four spatial directions, place the second part of the current collector system in the pocket, and cover the pocket with a steel plate (welded or otherwise connected to the rest of the steel conductor element).

[0021] After the copper current collector system is placed in the recess (e.g., in the shape of a pocket), a cover element can be used to completely "close" the recess and cover any accessible gaps between the copper current collector system and the steel conductor element within the recess.

[0022] In a preferred embodiment of the invention, the steel conductor elements are steel conductor bars, preferably rectangular in shape.

[0023] In a preferred embodiment of the present invention, the current collector system is at least partially coated with a protective steel sheet coating, and a first portion of the current collector system is at least partially, preferably completely, coated with the optional protective steel sheet coating.

[0024] Preferably, at least 50% of the surface of the current collector system is covered with the protective steel coating, more preferably at least 60%, even more preferably at least 70%, and most preferably at least 80%. In a particularly preferred embodiment, the surface of the current collector is completely covered with the protective steel. The above values ​​relate to the surface without taking into account the second portion arranged in the recess of the conductor element.

[0025] Preferably, at least 50% of the surface of the first portion of the current collector system is coated with the protective steel layer, more preferably at least 60%, even more preferably at least 70%, and most preferably at least 80%. In a particularly preferred embodiment, the surface of the first portion of the current collector system is completely coated.

[0026] This reduces the deleterious effects of diffusion of aluminum and other products that occur during operation of the electrolysis cell.

[0027] Preferably, the volume ratio of copper or copper alloy to the protective steel layer in the current collector system is at least 200%, preferably at least 300%, more preferably at least 400%.

[0028] Preferably, the thickness of the protective steel layer is 0.05 mm to 6 mm, more preferably 0.15 mm to 4 mm, and even more preferably 1.5 mm to 3 mm.

[0029] The protective steel layer may be made of or consist of a steel selected from carbon steel, low carbon steel, chromium-based steel, nickel-based steel or chromium-nickel-based steel or alloy steel.

[0030] In a preferred embodiment of the invention, the copper or copper alloy is in the form of a rod of rectangular cross section, protected on at least one face facing the cathode with a protective thin steel layer, preferably on all faces facing the cathode.

[0031] If the current collector system comprises a steel protective layer, i.e. is at least partially coated with a protective steel layer, the protective steel layer is in direct contact with the walls of the grooves of the carbonaceous cathode.

[0032] Preferably, the protective steel layer is coated with an additional upper and / or lower layer of copper, nickel, chromium, or graphite paint or film layer, more preferably the thickness of the additional upper and / or lower layer is between 1 μm and 1 mm.

[0033] The surface of the current collector system may be roughened or formed with recesses or protrusions such as grooves, fins or ribs to increase the surface area between the cathode and the current collector system and improve contact between the elements.

[0034] In a preferred embodiment of the invention, the current collector system, if it has a steel coating, is (further) coated at least in part with an insulator, in particular with a layer of insulating material such as alumina, insulating glue or cement or any insulating material that can withstand temperatures up to 1200°C.

[0035] In a preferred embodiment of the invention, the current collector system, and / or the steel protective layer if the current collector system is at least partially coated, is in direct contact with the carbonaceous cathode.

[0036] The steel cladding can be configured to be welded to the steel conductor element to completely "seal" the recess (e.g., pocket-shaped) and cover any accessible gaps between the copper current collector system within the recess and the steel conductor element.

[0037] The inventors have discovered that increasing the area of ​​direct contact enhances the beneficial effect. Thus, at least 50%, preferably at least 70%, more preferably at least 80%, and most preferably at least 90% of the surface of the second portion of the current collector system is in direct contact with the steel conductor element. In certain preferred embodiments, the entire surface of the second portion of the current collector system is in direct contact with the steel conductor element.

[0038] Preferably, at least 50% of the contact surface between the second part of the current collector system and the steel conductor element is formed by direct contact, more preferably at least 70%, and most preferably at least 80%. In a particularly preferred embodiment, the entire contact surface is formed by direct contact.

[0039] Since steel coatings on the current collector system can increase contact resistance, in preferred embodiments of the invention the second portion of the current collector system is at least partially, preferably completely, free from any protective steel coating.

[0040] The surface of the current collector system may be roughened or formed with recesses or protrusions such as grooves or fins to improve contact with the carbonaceous cathode.

[0041] In a preferred embodiment of the invention, the surface of the second portion of the current collector system that is not in direct contact with the steel conductor element is at least partially covered with a carbonaceous material, i.e., the carbonaceous material is located between the current collector system and the steel conductor rod.

[0042] Filling part of the volume between the copper current collector system and the steel conductor rods avoids excessive pressure buildup during electrolytic heating. Expanded graphite material is preferred because it is resistant to high temperatures and is an inert material that will not affect or contaminate the connections.

[0043] In a preferred embodiment of the present invention, the current collector system has a third portion different from the first and second portions, the third portion being disposed outside the recess of the steel conductor element and the groove of the carbonaceous cathode, and the third portion being surrounded by a protective shell, the protective shell being made of a material selected from SiC, ramming paste, a steel cover plate, a refractory material, or a mixture thereof. Most preferred is a shell having an inner layer made of SiC, ramming paste, a refractory material, or a mixture thereof, and an outer layer made of steel, the inner layer being disposed between the current collector system and the outer steel cover layer.

[0044] In a preferred embodiment of the invention, the second part of the current collector system, which is placed in the recess of the steel conductor element, has a pin shape, i.e. preferably a cylindrical shape. The advantage of such a shape is that a corresponding negative shape in the steel conductor element for fitting the second part can be easily formed by drilling. The pin can be pressed into the drilled hole to ensure a tight friction fit.

[0045] Preferably, the current collector system is made up of several elements, of which the element constituting the second part of the current collector system, which is placed in the recess of the steel conductor element, is connectable with the rest of the current collector system, in particular with the first part thereof, such connection being preferably realised by the pin-fit technique described above or other suitable joining techniques, ensuring friction and / or material joining at electrolysis temperatures (approximately 950°C).

[0046] Preferably, the current collector system comprises a current collector bar, preferably of rectangular shape.

[0047] In a preferred embodiment of the present invention, the cathode is a rectangular cathode block.

[0048] In a preferred embodiment of the invention, the recess in the steel conductor element has a volume V R and the second part of the current collecting system, which is located in the recess of the steel conductor element, has a volume V 2S and JPEG2025538203000002.jpg1613 is in the range of 0.9 to 1.0, preferably 0.92 to 0.98 under normal temperature conditions in accordance with DIN1341.

[0049] These values ​​allow for a thermally compatible design that ensures a reliable and stable connection. The minimal air gap between the materials, which already provides good contact at room temperature, is further improved by the high temperatures and thermal expansion of the materials. Because copper has a higher thermal expansion coefficient than steel when the cell is heated, a permanent high pressure is created between the materials, resulting in significant diffusion processes that strengthen the connection between them. Particularly preferred in this context is that the recess has the shape of a pocket, into which the second part of the current collection system is placed.

[0050] The present invention also relates to a kit of parts, i.e. a system of separate elements, for manufacturing a cathode current collector and connector assembly according to any of the preceding claims. The system comprises: a) a current collector system made of copper or copper alloy with an optional protective steel coating; b) a carbonaceous cathode having a groove for receiving a first portion of a current collector system; c) a steel conductor element having a recess for accommodating a second portion of the current collector system.

[0051] The present invention also relates to an aluminum electrolysis cell comprising an inventive cathode current collector, a connector assembly and a current supply bus bar, wherein the conductor elements of the cathode current collector and the connector assembly are electrically connected to the supply bus bar via a flexible material, preferably copper or aluminum.

[0052] The present invention further relates to the use of direct contact between a copper or copper alloy current collector system, optionally with a protective steel layer coating, and a steel conductor element in a cathode assembly of an aluminum electrolysis cell to reduce voltage drop in the aluminum electrolysis process.

[0053] example The present invention will now be described in more detail with reference to specific examples according to the invention and the accompanying drawings.

[0054] Examples of inventions A cathode block with a rectangular copper current collector system measuring 550 x 450 x 3200 mm (width x height x length) is provided with a groove measuring 44 x 130 mm (width x depth). A rectangular copper current collector system measuring 44 x 84 mm in cross section is placed within the groove. This consists of a 40 x 80 mm copper rod, covered with a 2 mm thick steel plate and coated with ramming paste. The rectangular steel conductor element has a cross section of 120 x 120 mm and a length of 300 mm. This element is provided with a pocket with a rectangular opening (width x depth x length: 80 x 80 x 160 mm) to accommodate the uncoated copper end of the collector rod, as shown schematically in Figure 2. The pocket accommodates a 150 mm long section of the copper end of the collector rod. The cavity is sealed with a flat steel plate and connected to the steel conductor element by welding. The remaining portion of the collector rod where the steel coating contacts the surface of the steel conductor element is welded to the steel conductor element to further protect the copper from aggressive compounds within the cell.

[0055] Comparative Example A cathode block with a copper current collection system measuring 550 x 450 x 3200 mm (width x height x length) is provided with a slot measuring 44 x 130 mm (width x depth). A copper collector system (44 x 84 mm cross-section) is placed within the slot. This system is comprised of a 40 x 80 mm copper rod, coated with a 2 mm thick steel plate and covered with ramming paste. The steel conductor element has a cross-section of 120 x 120 mm and a length of 300 mm. The conductor element has a pocket with an opening measuring 81 x 80.5 x 160 mm (width x depth x length) to accommodate the entire uncoated copper end of the collector rod, as shown diagrammatically in Figure 2. A 0.5 mm thick layer of electrically conductive adhesive is applied between the copper and steel surfaces. This pocket accommodates a 150 mm portion of the copper end of the collector rod. The cavity is sealed with a flat steel plate and connected to the steel conductor element by welding. The remaining steel coated portion of the collector rod that contacts the surface of the steel conductor element is welded to the steel conductor element to further protect the copper from aggressive compounds within the cell.

[0056] The adhesive-free assembly of the inventive example reduced the cathode voltage drop by 30 mV over the comparative example. [Brief explanation of the drawings]

[0057] Furthermore, additional advantages, features and possible applications will become apparent from the description of the preferred embodiment and the associated drawings.

[0058] [Figure 1] FIG. 1 shows a longitudinal cross-sectional view of the cathode current collector and connector assembly of the present invention. [Figure 2] FIG. 2 shows a partially exploded view of a portion of the cathode current collector and connector assembly of the present invention. [Figure 3] FIG. 3 shows the terminal end of the cathode current collector and connector assembly of the present invention. [Figure 4] FIG. 4 shows a longitudinal cross-sectional view of a cathode current collector and connector assembly of the present invention having pin-shaped current collector elements. DETAILED DESCRIPTION OF THE INVENTION

[0059] FIG. 1 shows a longitudinal cross-sectional view of a cathode current collector and connector assembly of the present invention, shown in its final operating position within an electrolysis cell. In this assembly, a cathode block 1 has a groove-like recess formed in its horizontal surface along its longitudinal direction (x-axis direction), in which a first portion of a current collector rod 2 is disposed. Typically, the current collector rod is in direct contact with the cathode block, or a conductive carbide layer (e.g., ramming paste) is disposed between the surfaces. The cathode current collector and connector assembly further includes a conductor element 3, preferably made of steel, in which a second portion of the current collector system is disposed.

[0060] FIG. 2 shows a partially exploded view of the cathode current collector and connector assembly of the present invention, illustrating the connection between the conductor element and the current collector system. This section consists of two longitudinal current collector rods 2, each coated with a protective steel layer at its first portion. This first portion is placed in a groove in the carbonaceous cathode (not shown). The current collector rods further have a second, uncoated portion 5, which is placed in a recess (here, pocket-like) in the conductor element 3. In the illustration, one of the current collector rods 2 is already positioned in the recess in the conductor element 3. The other current collector rod 2 is inserted into the pocket, which restricts the movement of the uncoated portion 5 in four of the six spatial directions. After the uncoated portion is positioned in the pocket, the pocket is closed with a steel plate 6, which restricts the movement of the uncoated portion in an additional spatial direction.

[0061] FIG. 3 shows the terminal end of a cathode current collector and connector assembly of the present invention. In this assembly, the cathode block 1 has two recessed grooves in its horizontal surface, into which the first portions of two current collector rods are placed. The current collector rods protrude from the grooves and are connected to the conductive element 2 by placing their second portions in the recesses of the conductive element. The third portion of the current collector rod protruding from the grooves is not placed in the recesses of the conductive element and is therefore embedded in a protective shell 7 formed of a refractory material and an outer steel plate. For transportation, the current collector rods are fixed to the carbonaceous cathode 1 by fixing means 8.

[0062] FIG. 4 shows a longitudinal cross section of a cathode current collector and connector assembly of the present invention having a pin-shaped current collector element 9. In this assembly, a cathode block 1 has a recessed groove in its horizontal surface along its longitudinal direction (x-axis direction), within which a first portion of a current collector rod 2 is disposed. Typically, the current collector rod is in direct contact with the cathode block, or a conductive carbon layer (e.g., ramming paste) is disposed between the surfaces. The cathode current collector and connector assembly further comprises a conductor element 3, preferably made of steel, and a structure having the recess. The current collector system further comprises a pin-shaped connecting element 9 disposed within the recess of the current collector rod and the steel conductor element, thereby providing an electrical connection between the elements. [Explanation of symbols]

[0063] 1 cathode block 2 (coated) current collector rods 3 Conductor elements 4 recess 5 Second part of current collector rod 6 steel plate 7 Protective Shell 8 Fixing means 9-pin shaped current collector element

Claims

1. 1. A cathode current collector and connector assembly for an aluminum electrolysis cell, comprising: a) a current collector system made of copper or a copper alloy, the current collector system having an optional protective steel layer coating at least partially covering the current collector system; b) a carbonaceous cathode having a groove for receiving a first portion of the current collector system; c) a steel conductor element having a recess for receiving a second portion of the current collector system; Equipped with a first portion of the current collector system disposed in a groove of the carbonaceous cathode; A cathode current collector and connector assembly, wherein a second portion of the current collector system is in at least partial direct contact with the steel conductive element.

2. 2. The cathode current collector and connector assembly of claim 1, wherein the steel conductor elements are preferably rectangular steel conductor bars.

3. 3. A cathode current collector and connector assembly according to claim 1 or 2, wherein the current collector system is at least partially coated with the optional protective steel layer coating, and a first portion of the current collector system is at least partially, preferably completely, coated with the optional protective steel layer coating.

4. A cathode current collector and connector assembly according to any of claims 1 to 3, wherein the second part of the current collector system is at least partially, preferably completely free from any protective steel layer coating.

5. 5. The cathode current collector and connector assembly according to claim 1, wherein the current collector system is coated with the optional protective steel coating, and the steel coating and the steel conductor rod are partially connected by welding.

6. 6. A cathode current collector and connector assembly according to claim 1, wherein a surface of the second part of the current collector system that is not in direct contact with the steel conductor element is at least partially coated with a carbonaceous material.

7. 7. A cathode current collector and connector assembly according to any one of claims 1 to 6, wherein the current collector system has a third part different from the first and second parts, the third part being located outside the recess of the steel conductor element and the groove of the carbon cathode, the third part being surrounded by a protective shell, the protective shell preferably made of a material selected from SiC, ramming paste, a steel cover plate, a refractory material or a combination thereof.

8. 8. A cathode current collector and connector assembly according to any one of claims 1 to 7, wherein the second part of the current collector system, located in the recess of the steel conductor element, has a pin shape or is preferably separable from the rest of the current collector system.

9. A cathode current collector and connector assembly according to any of claims 1 to 8, wherein said current collector system is a current collector bar, preferably of rectangular shape.

10. The recess of the steel conductor element has a volume V Ｒ and a second portion of the current collector system disposed in a recess of the steel conductor element has a volume V ２Ｓ and A cathode current collector and connector assembly according to any of the preceding claims, wherein under normal conditions in accordance with DIN 1341, is in the range of 0.9 to 1.0, preferably 0.92 to 0.

98.

11. a) a current collector system made of copper or copper alloy with an optional protective steel coating; b) a carbonaceous cathode having a groove for receiving a first portion of the current collector system; c) a steel conductor element having a recess for receiving a second portion of the current collector system; Equipped with Kit components for manufacturing the cathode current collector and connector assembly of any of claims 1 to 10.

12. An aluminum electrolysis plant or aluminum electrolysis cell, comprising: A cathode current collector and connector assembly according to any one of claims 1 to 10; A supply bus bar; Equipped with 10. An aluminium electrolysis plant or aluminium electrolysis cell, wherein the conductor elements of said cathode current collector and connector assembly are electrically connected to said current supply bus bar by flexible conductors, preferably of copper or aluminium.

13. 1. Use of a copper or copper alloy current collector system with an optional protective steel layer coating in direct contact with a steel conductor element in a cathode assembly of an aluminum electrolysis cell to reduce voltage drop in an aluminum electrolysis process.

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