EP4082065A1

EP4082065A1 - Electrochemical sodium metal halide battery, and method for producing same

Info

Publication number: EP4082065A1
Application number: EP20845384.5A
Authority: EP
Inventors: Martin Hofacker
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2019-12-23
Filing date: 2020-12-22
Publication date: 2022-11-02
Also published as: DE102019135752A1; WO2021129905A1; US20230041604A1; DE112020006292A5; KR20220119068A; CN114930604A; AU2020415178A1; JP2023508404A

Abstract

The invention relates to an electrochemical sodium metal halide battery, in particular a sodium nickel chloride battery for high-performance batteries of electric vehicles and other demanding stationary applications. The problem addressed by the invention is that of providing an electrochemical sodium metal halide battery which makes it possible to have a current collector (1) with a maximum surface-to-cross-section ratio, to manufacture same in a simple manner, and to fill the electrodes of the battery in a simplified manner. This problem is solved according to the invention in that: a metal cathode-side current collector (1), that is elongated in a cathode chamber (21) about a central axis (51), is manufactured from a metal tube (11) having a high electrical conductivity; in a portion of the current collector (1) plunged into a separator (3), said current collector has a shaped tube section (11, 12) which is provided with elements for increasing the surface area (15, 16, 18, 19) of the current collector (1); and, at a transition between an unpressed tube section, that acts as a filling tube (13), and a pressed tube section (12), said current collector has at least one through-hole (14) that opens the filling tube (13) outwardly, meaning that the filling tube (13) can be used as a filling opening for the porous mixture of the cathode (2) and the secondary electrolyte (22).

Description

Sodium metal halide electrochemical cell and process for its manufacture

The invention relates to an electrochemical sodium metal halide cell, containing a housing with a central axis, a separator which is equidistant from the housing and which is extended around the central axis of the housing and which, as a solid primary electrolyte, separates an anode compartment from a cathode compartment in an electrically insulating and hermetic manner, but is permeable for sodium ions, a cathode filling the cathode compartment made of a porous mixture of metal powder and metal halide powder granules and a secondary electrolyte made of a sodium metal halide molten salt and a metallic cathode-side which is elongated around the central axis in the cathode compartment and impregnated the cathode compartment and the porous mixture of the cathode Current collector, as well as a method for manufacturing the electrochemical cell. The invention is preferably used as a sodium metal halide cell, in particular as a sodium nickel chloride cell, in high-performance batteries for electric vehicles and demanding stationary applications.

The above-mentioned electrochemical cells contain an anode consisting of at least one metal in the charged state and a cathode, usually in a porous form, made of transition metals and metal halides (e.g. sodium, nickel, iron, copper, aluminum), which is at least liquid in the operating state Molten salt is soaked for ion conduction, and a metallic current collector for making electrical contact with the cathode.

From the prior art of accumulators and secondary batteries it is known that electrochemical cells based on sodium-metal halide chemistry are used in particular for high-performance batteries in electric vehicles and demanding stationary applications because they have high specific power and energy densities and a long cycle life . This is a thermal battery in which the anode is formed by a thermally liquefied alkali metal (sodium) and the cathode is formed by a liquid molten salt that impregnates a porous material made of metals and metal halides (e.g. nickel chloride and sodium chloride) and the two electrodes are separated by an electrically insulating separator that acts as a solid electrolyte (e.g. sodium ß-aluminate with the largest possible ß “phase, which conducts sodium ions very well from 270 ° C, ie is permeable to sodium ions ). Such batteries have no electrochemical self-discharge and have an energy efficiency of approx. 90% and a Coulomb efficiency of 100%.

In this context, US 2015/0004456 A1 describes a current collector for a sodium metal halide cell in which a lamellar design of the current collector results in high performance and cost savings in the electrochemical Cells should enable. The current collector has at least one flat elongated fin made of electrically conductive material, has a bend with respect to its dominant longitudinal axis and is welded or soldered with the bent upper end to a flat metal ring, which fixes the current collector to the cell cover with exactly centered alignment of the fin (n) allowed in the cell axis. In a preferred embodiment, two complementarily slotted lamellae with a center kept free for a carbon felt are arranged in a crossed manner. A disadvantage, however, is on the one hand, in all differently designed forms of the current collector, the requirement to connect the lamellae with the metal ring in a materially and precisely aligned manner and, on the other hand, that a carbon felt with not inconsiderable dimensions must be positioned between the metal sheets to store the liquid molten salt that is only partially fixed in its position. Since the carbon felt itself takes up space, the electrical storage capacity of the Na / MC ^ cell is reduced. If the carbon felt is not positioned exactly, locally different current densities result, due to cathode areas of different thicknesses, and thus the cell properties can differ from cell to cell.

The invention is based on the object of finding a new way of realizing an electrochemical sodium metal halide cell, which enables the current collector to be designed with a maximum surface-to-cross-section ratio, while aligning it along the axis of symmetry of the electrochemical cell to achieve a uniform current density distribution in the electrode around the current collector and a simple manufacturing position of the same as well as a simplified assembly of the electrochemical sodium metal halide cell with regard to the filling with the electrode components are permitted. An expanded object of the invention is to integrate the function of the spatial intermediate storage of the molten salt in the current collector.

According to the invention, the object is in an electrochemical sodium metal halide cell, comprising a housing with a central axis, a separator which is equidistant from the housing and which is extended around the central axis of the housing and which, as a solid primary electrolyte, separates an anode chamber from a cathode chamber in an electrically insulating and hermetic manner But sodium ions are permeable to sodium ions, a cathode that fills the cathode compartment made of a porous mixture of metal powder and metal halide powder granules, as well as a secondary electrolyte from a sodium-metal halide salt melt that impregnates the cathode compartment and the porous mixture of the cathode and one in the cathode compartment around the central axis elongated metallic cathode-side current collector, characterized in that the current collector is a metal tube with a high electrical conductivity of s> 106 S / m, which is in the porous mixture of granules of the cathode and in the secondary in the separator electrolyte immersed and designed as a pressed pipe section on the inside so narrowed that no granulate of the cathode, but only secondary electrolyte can penetrate, and is provided on the outside with elements to increase the surface area of the current collector, and that the current collector is an unpressed pipe above the immersed, pressed pipe section section as a filler pipe for filling the cathode space, at a transition from the pressed pipe section to the unpressed pipe section of the filler pipe at least one through hole opening the filler pipe to the outside, so that the filler pipe for filling the porous mixture of granules of the cathode into the cathode compartment is only outside of the pressed pipe section and for filling the entire cathode space with secondary electrolyte.

The current collector in the pressed pipe section advantageously has a carbon felt which was inserted into the pressed pipe section before pressing.

The current collector expediently has a carbon felt in the pressed pipe section, which after pressing and removal of a pinch edge of the pressed pipe section can be pushed laterally into the pressed pipe section.

The current collector preferably has punchings, preferably in the form of through holes, in the pressed pipe section as elements for increasing the surface area. The current collector has metal tufts of metal strips or wires made of a metal that has not been attacked by the electrochemical processes of the cell and has a conductivity comparable to that of the metal pipe of the current collector, in the pressed pipe section in the through holes.

A commercially available nickel, aluminum or copper pipe is expediently used as the current collector.

In the current collector, the elements for increasing the surface area are designed with at least one element from the group of punched through holes or other relief-forming structures with pinch edges, tufts of metal, fins or folded sheets. The metal tufts are preferably made from metal strips or wires made of nickel or molybdenum.

It proves to be particularly advantageous if the metal tufts of metal strips or wires are aligned in such a way that local resistance gradients in the cathode space are minimized or evenly distributed over the cross section of the cathode space.

In a further advantageous embodiment, the metal strips or wires used in the metal tufts have a length that is selected to be smaller, the higher the cell capacities are to be achieved, and the greater the length, up to the maximum of the separator, the higher it is Services are to be taken from the cell. The unpressed pipe section of the filler pipe of the current collector is preferably closed with a cohesively fastened sheet metal blank or a deep-drawn part after the porous mixture of the cathode and the secondary electrolyte has been filled. Alternatively, it is useful that the unpressed pipe section of the filler tube of the current collector is squeezed or hermetically sealed with a solder or weld seam after the porous mixture of the cathode and the secondary electrolyte has been filled in at the upper end of the filler tube.

The pressed pipe section of the current collector can preferably be pressed flat by the action of force from two collinear directions.

In a further advantageous embodiment, the pressed pipe section of the current collector is pressed into a star-shaped cross section from at least three evenly distributed directions offset around the central axis.

The pressed pipe section of the current collector is preferably pressed by the above-mentioned forces in such a way that an interior space that forms as a secondary electrolyte reservoir is just as large as a volume of the secondary electrolyte that is necessary for the complete wetting of the current collector when the cell is fully charged , is held up.

It also proves to be expedient if a metal pipe is attached below the pressed pipe section of the current collector, which is fitted with radial fins which are inserted into tangentially equidistant slots in the metal pipe.

In another advantageous embodiment, a metal tube with radial fins is attached below the pressed tube section of the current collector, which is produced from an equidistantly folded sheet metal and its axially symmetrical bend.

Furthermore, the object is achieved in a method for setting up an electrochemical sodium metal halide cell with the following steps:

- Provision of a housing for the formation of an anode compartment, a separator that can be used equidistantly to the housin se as an electrically insulating, solid primary electrolyte only permeable to sodium ions for separating the anode compartment from a cathode compartment, a cathode made of a porous mixture of metal powder and metal halide granules and one Secondary electrolyte for soaking the porous mixture of the cathode,

- Fierstellen a cathode-side current collector made of a metal tube, which is formed into a compressed pipe section current collector by forces acting radially on a central axis and in which an unpressed pipe section remains as a filler pipe at the upper end, with at least one transition from the pressed pipe section to the filler pipe Through-hole is introduced, which is provided as an outlet opening of the filler pipe for filling the cathode compartment, - Production of a cell closure from a cathode closure part with a central opening for the implementation of the filler pipe of the current collector in the central opening of the cathode closure part and material connection of the cathode closure part with an insulator joining ring and material connection of an anode closure part to the insulator joining ring,

- Positioning of the current collector collinear with the central axis in the separator as well as the equidistantly arranged housing around the separator by means of the cell closure made of insulator joining ring and anode closure part through a one-step joining process as well as cohesive connection of the joining points,

- Filling the porous mixture of metal powder and metal halide powder granules of the cathode through the filler tube of the current collector and the at least one through hole of the filler tube into the cathode space in the separator only outside the current collector and then pouring the secondary electrolyte in liquid form with the exclusion of oxygen and

- Final hermetic sealing of the electrochemical cell by cohesive Ver close the filler pipe.

Expediently, elements for increasing the surface area of the current collector are introduced equidistantly into the pressed pipe section in the form of through holes. However, they can also be introduced into an unpressed pipe section and / or formed as elements from the group of other relief-forming structures with pinch edges, metal tufts, fins or folded sheets in the pressed or unpressed pipe section.

It has proven to be particularly advantageous to insert metal tufts made of metal strips or wire into the through holes.

The pressed pipe section of the current collector is preferably formed flat by collinear radial force.

In an alternative variant, the pressed pipe section of the current collector is advantageously formed in a star shape by a plurality of radial force effects evenly distributed around the central axis.

In a further preferred embodiment of the current collector, radial fins are attached to the metal pipe below the pressed pipe section to increase the surface area of the current collector and are inserted into tangentially equidistant slots.

Furthermore, to increase the surface area of the current collector below the pressed pipe section on the metal pipe, radial fins can be produced by a folded sheet metal that is either wound around the metal pipe or is itself bent to form a body with a tubular interior. The filling pipe is expediently closed by welding or soldering the upper end of the pipe to a sheet metal blank. Alternatively, the filling pipe can also be closed by squeezing the top end of the tube and then welding or soldering the squeezed top end of the tube.

The invention shows a possibility of how a current collector is to be designed for an electrochemical sodium metal halide cell in order to achieve an axially symmetrical current distribution within the electrolyte material and an uncomplicated filling of the cathode components and a technologically simple and inexpensive production of the current collector and its assembly in the to achieve electrochemical cell. By increasing the surface of the current collector, the contact resistance to metallic components of the cathode is reduced, as a result of which the internal resistance or the power loss of the cell is reduced and the efficiency is increased.

The invention is explained in more detail below on the basis of exemplary embodiments and illustrations. Show:

1: a schematic representation of the principle of a cathode-side current collector according to the invention, produced from a metal tube with stampings which is pressed in sections;

FIG. 2 shows a further embodiment of the current collector on the cathode side according to FIG. 1 with round punchings through which tufts of metal wire are traversed; FIG.

FIG. 3: a schematic sectional illustration of the detail A from FIG. 1 with a continuous punching in the transition area from the filler pipe to the pressed pipe section of the current collector; FIG.

FIG. 4: a schematic representation of the current distribution in the cathode space within the radial plane B marked in FIG. 2, which intersects a bore with an inserted metal wire tuft in the pressed tube section of the current collector; FIG.

5: a preferred embodiment of the electrochemical sodium metal halide cell with a separator made of sodium β-aluminate and a cathode-side current collector made of nickel-plated copper tube;

6 shows a further embodiment of the current collector according to the invention after the metal pipe has been pressed with the pinch edge removed on one side, preferably for inserting a carbon felt;

FIG. 7: the design of the current collector from FIG. 6 after the cathode materials have been filled in, with the upper end of the filler tube finally squeezed and fused; FIG. 8: a further embodiment of the current collector according to the invention with finally squeezed and fused upper pipe end of the filler pipe, the lower pressed pipe section of the metal pipe being pressed together centrally from several non-parallel radial directions;

FIG. 9: a cross section of the embodiment of the current collector according to FIG. 8, in which the lower pressed pipe section is pressed from four orthogonal radial directions, two of which are directed collinearly opposite to the pipe axis.

Fig. 10: Another embodiment of the current collector according to the invention according to Fig. 8, wherein the filler pipe with finally squeezed upper pipe end is attached to a metal pipe pressed separately from four orthogonal radial directions as a lower pipe section, with cross-sectional differences between the filler pipe and the radially pressed metal pipe the punchings for replace the filler openings;

11: the further embodiment of the current collector according to the invention with a filler pipe, a pressed pipe section and a metal pipe fitted with radial fins, which has a reservoir for the secondary electrolyte inside;

12: a further embodiment of the current collector according to FIG. 11, in which the fins are simulated by an equidistantly folded sheet metal and the metal tube is simulated by the axially symmetrically bent sheet metal;

FIG. 13 shows a section of a double cell arrangement of the electrochemical cell, expanded compared to FIG. 5, with a double-walled separator, which contains the anode compartment, and inner and outer cathode compartment with respective current collectors.

An electrochemical sodium metal halide cell according to the invention comprises, in an exemplary basic structure, a cathode-side current collector 1, a cathode 2 made of sodium salt and a further metal halide, a separator 3 which, as a solid primary electrolyte, separates a cathode compartment 21 from an anode compartment 41, a secondary electrolyte 22, which passes through the cathode compartment 21 with the current collector 1, an anode 4 and a housing 5 which represents the anode-side current collector.

Fig. 1 shows a preferred embodiment of the cathode-side current collector 1, which starts from a tubular base body (metal tube 11) made of an electrically conductive metal (s> 10 ⁶ S / m) in a lower pressed tube section 12, which is located in the cathode space 21 extends along the central axis 51 of the separator 3, and an upper, unpressed tube section, which forms a filler tube 13 for the cathode material above the cathode space 21, is subdivided. The initially unpressed metal pipe 11 and the remaining filler pipe 13 can also be made square, polygonal, corrugated or otherwise deviating from a circular geometry in their cross-sections. As much secondary electrolyte 22 is temporarily stored in the pressed pipe section 12 as is required in the fully charged state for the complete wetting of the porous cathode 2. The cathode 2 can refill the liquid secondary electrolyte 22 from the interior of the current collector 1 during charging, during which the volume of the porous cathode granulate is reduced by approx. 20%. For good electron conduction and thus a reduced internal resistance of the Na / metal halide cell, the length of the current collector 1 should come as close as possible to the bottom of the separator 3. Its length should therefore be chosen to be significantly greater than 70% of the length of the separator 3, with tubular Na / metal chloride cells advantageously being manufactured with lengths between 50 mm and 500 mm. The electrical storage capacity is determined by the cathode space 21 filled with porous cathode 2 between the outer contour of the current collector 1 and the inner wall of the separator 3, so that the diameter of the current collector 1 is particularly advantageously between 4 mm and 50 mm if the diameter of the separator 3 is assumed to be 15 mm to 90 mm. If elements for increasing the surface area are attached to the current collector 1, as will be described in more detail below, adapted diameters of 10 mm to 80 mm of the outer contour of the current collector 1 can also be used for the assumed diameters of the separator 3.

Nickel or nickel alloys or molybdenum can be used as materials for the current collector 1. For more economical production of the current collector 1, commercially available metal pipes 11 from mass production, e.g. B. made of copper or a copper alloy, which can be easily deformed (pressing, punching, bending), are inexpensive and lower the resistance of the electrochemical cell due to a very high electrical conductivity.

For reasons of cell chemistry, after the deformation of the metal tube 11 and the punching of slots or through holes 14, the current collector 1 is protected from chemical erosion by a nickel coating. Is z. If, for example, a cathode 2 with ZnCl2 or FeC ^ granulate is used, then the current collector 1 can be made of copper if the cell voltage is selected to be lower than the voltage from which the copper (approx. 2.6 V) with the salt over the secondary electrolyte 22 reacts to form CuCl or CuCl2. The use of nickel or molybdenum as a protective layer is, however, a reliable option for protecting the current collector 1 from being eroded, so that even aluminum tubes can be used. However, depending on the cell chemistry (e.g. CuCI, COCI2, CrCl2 or ZnCy), other material combinations can also be selected.

Are in the manufactured through holes 14 (z. B. punched before, during or after the pressing) of the metal pipe 11 additional metal tufts 15 in the form of metal strips or metal wires made of z. B. nickel or molybdenum is introduced, the surface of the current collector 1 is significantly increased and in particular with a flat pressed pipe section 12 to a approximated cylindrical outer contour. Instead of metal wires, rods (not shown) can also be used. By using molybdenum instead of nickel, when using a cathode 2 made of FeCl _2, for example, the maximum charging voltage can be higher and the conductivity is even better (Mo: 18.2-10 ⁶ S / m; Ni: 13.9-10 ⁶ S / m) the performance of the cell can also be increased.

By varying the wire lengths of the metal tufts 15, their diameter, number and orientation, a very uniform decrease in resistance of the cathode 2 in the cathode space 21 towards the separator 3 can take place.

The performance of the cell can be significantly influenced by either reducing the number and size (wire lengths and diameter) to a minimum and thus optimizing the Na / MCl2 cell for storage capacity or by having many wires of the metal tufts 15 adapted to the cathode compartment 21 Find use, which subsequently leads to a reduction in capacity but increased performance. Metal tufts 15 reaching up to the separator 3 also have the effect that the electrons no longer - as is customary in the prior art - take the path via the individual metal particles in contact with one another, but rather a faster transport via the wires of the metal tufts 15 than Solids can take place, since in the charged state the amount of non-chlorinated, electrically conductive metal is reduced and the charging or discharging reaction always begins at the shortest distance from the separator 3.

As an exemplary embodiment, a metal tube 11 approximately 300 mm long and 5 mm in diameter is assumed, which leads to an active surface (which is in contact with the cathode 2 with a flea of 270 mm) of approximately 42.6 cm ² . If the metal pipe 11 is provided with thirteen through holes 14 and each through hole 14 (except for the top through hole 14 on the filler pipe 13) with metal tufts 15 each made of thirteen 0.7 mm thick and approx. 32 mm long wires, the surface area of the metal tufts is 15 additional 110 cm ² , with 1 mm thick wires even 160 cm ² , with the additional advantage that the fast electron coupling paths (wires) reach as far as the separator 3. With this exemplary embodiment of the shaping of the current collector 1, the surface of the cathode-side current collector 1 can be increased by a factor of five (from approx. 40 cm ² to 200 cm ² ). Instead of metal wires, sheet metal strips can also be attached, joined or pressed with it in or on the metal tube 11.

For a sufficient current resistance, the material cross-section of the metal tube 11 is to be adapted accordingly to the requirements.

If pressing in, spreading or bending over with, if necessary, additional coating of the wires or sheets of the metal tufts 15 with the pressed pipe section 12 is not sufficient to fix them against slipping or to sufficiently reduce the transition resistance, it is possible to use a To fix the welding or soldering process. It can also be a Material with a lower conductivity than copper can be used as the base material for the wires, rods or sheets of the metal tufts 15 in order to then cover them together with the pressed pipe section 12 with a chemically resistant protective layer, e.g. B. made of nickel, molybdenum, if the cell chemistry and thus the charging voltage is adjusted accordingly. Base materials from z. B. copper or nickel can also be coated with graphene to further increase the conductivity.

The measure of the metal tufts 15 (preferably made of metal wires) used to increase the surface area in the case of a pressed current collector 1 brings with it a further significant advantage, which is that the current distribution in a preferably used cylindrical separator 3 is more homogeneous because from the flat Differences in the radial resistance gradients resulting from the shape of the pressed pipe section 12 are minimized or more evenly distributed around the central axis 51. Such a homogenized current distribution of the current collector 1 according to the invention within a cylindrical separator 3 is shown qualitatively in FIG. A similar behavior of the current distribution is achieved with a star-shaped pressing of the metal tube 11 for the current collector 1 as shown in FIG. 9. Furthermore, the press shape of the metal pipe 11 can also be matched to the contour of the separator 3.

The most uniform current density distribution within the cathode space 21, which can be generated in a rotationally symmetrical separator 3, is ensured by a current collector 1 in the form of an unpressed metal tube 11, which is likewise round and arranged in the center of the cathode space 21. This metal tube 11 can then only be pressed in an upper, only a few millimeters long, pressed tube section 12, so that the area designated as the filler tube 13 for filling the cathode space 21 and at the same time the internal volume of the current collector 1 as a reservoir 24 for the secondary electrolyte 22 below the pressed pipe section 12 remains free. The tubular current collector 1 can then either be pressed in at the lowest end area so that only the molten salt of the secondary electrolyte 22 can penetrate into the secondary electrolyte reservoir 24, or the metal tube 11 is pressed a few centimeters above the lowest end area so lightly that a carbon felt 23 can be inserted up to this stop and the penetration of z. B. as a granulate filled cathode 2 prevents.

In a further embodiment, the carbon felt 23 is positioned up to a few millimeters long, pressed tube section 12 in area A within the current collector 1, so that the carbon felt 23 protrudes from the metal tube 11 or is flush with it. The metal tube 11 does not have to have a closed contour, but only has to ensure that the reservoir 24 is infiltrated with the secondary electrolyte 22 and that no granules of the cathode 2 can penetrate. Thus, there are also slots along or across the center axis of the Metal pipe 11 is permitted, but not in the filling pipe 13 in the region of the cathode closure part 61 to outside the cell (because of the required cell tightness).

In a further embodiment, the metal pipe 11 can be filled with a rolled up carbon felt 23 before pressing to such an extent that a cavity remains only in the upper pipe section, the filler pipe 13. Subsequently, the current collector 1 provided with a carbon felt 23 is pressed and perforated in the metal tube 11, which will later be in contact with the cathode 2, and preferably - according to the embodiment of FIG. 2 - provided with metal tufts 15 of metal wires, the uppermost through hole 14 in the transition area remains free between the pressed pipe section 12 and filler pipe 13, d. H. that no metal tuft 15 is inserted because this through hole 14 - as can be seen in FIG. 3 from the enlarged detail A of FIG. 1 - is intended for filling with the granulate of the cathode 2 and then for the liquid infiltration of the secondary electrolyte 22.

There is the possibility that the pressed tube section 12 or an unpressed metal tube 11 has at least one further through hole 14 below the uppermost through hole 14 provided for cathode filling, which does not contain any metal tufts 15, so that the secondary electrolyte 22 consists of the carbon felt 23 or from the reservoir 24 can also emerge in the unpressed metal tube 11 from the interior of the current collector 1 and uniformly wet the granules of the cathode 2.

Instead of pressing the metal tube 11 of the current collector 1 flat, structures can also be embossed into the metal to increase the surface area (waves, grooves, grooves, slots, etc.).

The filling process of the cathode 2 as a mixture of granulated metal powders, such as. B. nickel, iron, aluminum, but also copper, cobalt, chromium or zinc, which are only converted to metal halides when the cell is later charged, and a sodium halide, such as sodium chloride, iodide, bromide or fluoride, then takes place in the in a stylized manner shown in FIG. 3 by pouring in the metal and metal halide powders in the form of pressed granules. The granules of the cathode 2 then hit the pressed tube section 12 and are deflected laterally through preferably two openings of the non-pressed uppermost through hole 14. For good flowability, the dimensions of the through hole 14 or further through holes 14 in the filler pipe 13 must be adapted to the granulate size of the cathode 2.

The larger the surface of the cathode-side current collector 1, the lower the contact resistance between the porous metal network (formed for example by non-chlorinated nickel or iron in the cathode granulate) and the current collector 1. If, for the aforementioned purpose, the current collector 1 were to be formed as a metal tube 11 with an enlarged diameter, the inner cavity of the metal tube 11 being available as a reservoir 24 for the secondary electrolyte 22, its electrically conductive surface would also increase, but the storage capacity would then be unnecessarily reduced because from a certain internal volume of the metal tube 11, more secondary electrolyte 22 is stored in the reservoir 24 than would be necessary for the charging process, and the cathode space 21 remaining for the granulate of the cathode 2 is reduced.

The invention therefore provides, as an expedient design of the cathode-side current collector 1, a reduced internal volume and an increase in the surface area, as well as a shape of the outer contour that is spatially adapted to the cylindrical separator 3. In a preferred embodiment, which is designed by a flat pressed pipe section 12 with through holes 14 and metal tufts 15 of metal strips or wires inserted therein, as can be seen in plane B of FIG. 2 from the sectional view of FIG Pressed bundles of metal strips or metal wires pushed into the through holes 14 are matched to a cylinder-like external shape of the current collector 1 by subsequent fanning and upsetting, which results in a uniform radial resistance distribution in the cathode space 21 of the separator 3.

The diameter of the metal tube 11 is determined by the size and flowability of the granules of the cathode 2 or the diameter of the through holes 14 designed as a filling opening required for a filling time to be observed. The through holes 14 used for increasing the surface area of the current collector 1 can, however, differ. By varying the wire lengths, diameters, their number and orientation, a very uniform, exact decrease in resistance in the cathode 2 can then take place.

5 shows a preferred embodiment of the electrochemical cell according to the invention as a schematic (not to scale) representation of an axial section of the cell. In the drawing, the essential components of the electrochemical cell are shown in a basic spatial arrangement and these are implemented with a specific embodiment in the sense of a special cell chemistry.

In the configuration of the cell according to FIG. 5, the cathode-side current collector 1 is made of a copper tube which is provided with a nickel coating to increase the chemical resistance. The use of copper or aluminum as the base material of the metal tube 11 lowers the electrical resistance of the current collector 1 due to the higher electrical conductivity, due to the thin-walled hollow structures and a cathode 2 made in comparison to a solid nickel body, the manufacturing costs are reduced and the forming (pressing and punching), since the wall thicknesses are less than those of a non-hollow body despite the larger surface. In an alternative embodiment, the current collector 1 can also be made entirely of nickel. As an alternative to the cell structure shown in FIG. 5, the cathode 2 can also be arranged outside the separator 3. It can then either exclusively outside the separator 3, i.e. inverted compared to the structure of FIG. 5 (not shown), or in the case of a double-walled design of the separator 3 with an enclosed anode space 41 - as shown in FIG. 13 - to this double-walled structure of the Separator 3 can be arranged both inside and outside, as is known in principle from WO 2018/138740 A1.

The cathode-side current collector 1 made of nickel-plated copper tube according to FIG. 5 is manufactured in the form according to FIG. 2 and aligned collinearly with the axis of the separator 3. The separator 3 divides the inner volume of the housing 5 acting as anode-side current collector into an outer anode space 41, which in this example is filled with metallic sodium as anode 4 in the charged state, and the inner cathode space 21, which in this embodiment is sbeispiel with granules made of nickel / NaCl (uncharged state) or nickel / NiCl2 (fully charged state) is filled, which were poured through the upper pipe section, the so-called filler pipe 13 of the current collector 1. In order to ensure rapid filling of the cathode space 21 with cathode granulate and also to achieve a low internal resistance, the cross section of the metal tube 11 and the through hole 14 must be adapted to the volume of the cathode 2 and the entire cell dimension.

In this embodiment of FIG. 5, the pressed pipe section 12 of the current collector 1 is equipped with metal tufts 15 made of metal wires in the punched through holes 14. The metal tufts 15 used to increase the surface area can consist of nickel or molybdenum wires. The through holes 14 can, for example, be punched before, during or after the pressing of the metal tube 11 in order to subsequently additionally enclose them with metal tufts 15, e.g. B. made of nickel or molybdenum to fill and so to increase the surface of the current collector 1 considerably. Gold-plating of the current collector 1 and its metal tufts 15 would further reduce the resistance of the current collector 1, but would increase the production costs.

Furthermore, the cathode space 21 within the separator 3, which is made as a solid primary electrolyte from sodium β-aluminate, is filled with a liquid secondary electrolyte 22, which in this example consists of sodium tetrachloroaluminate (NaAlCU). So that only the secondary electrolyte 22 and no Ni / NaCI granules can get into the interior of the current collector 1 below the filler pipe 13, the metal pipe 11 contains either a carbon felt 23 inside, which was inserted into the metal pipe 11 before pressing and pressed in with it, or the Gap dimensions of the pressed pipe section 12 below the filler pipe 13 and the lowermost end of the pressed pipe section 12 are sufficiently small.

The assembly of the current collector 1 on the cathode side in the electrochemical cell can advantageously be carried out as a one-step joint, which, depending on the design, is carried out with different Atmospheres and temperatures takes place in suitable ovens. In the one-step joining, the ceramic-ceramic composite between the separator 3 and the ceramic insulator joining ring 63, the z. B. can consist of corundum, as well as the metal-ceramic composite between the separator 3 and a metallic cathode closure part 61 and a metallic anode closure part 64 for hermetically sealing the electrochemical cell realized with a single joining step. For this purpose, the metallic closure parts 61 and 64 are advantageously manufactured by deep drawing. The cathode closure part 61 which closes the cathode space 21 is provided with a central opening into which the current collector 1 with one of the embodiments according to the invention, e.g. B. is introduced with the pressed pipe section 12 provided with metal tufts 15 and is welded or soldered to the unpressed pipe section, the filler pipe 13, before joining. In another embodiment, the filler pipe 13 is soldered to the metallic cathode closure part 61 during the one-step joining or is only welded to it after the joining process.

During the joining step of the one-step joining, the separator 3 or z. B. the housing 5 with its dimensions the necessary free spaces in the furnace. Positioning the current collector 1 within the separator 3 therefore does not increase the required free space and does not represent a disadvantage.

During the one-step joining, the anode closure part 64 is also used as a further z. B. deep-drawn part made of metal at a suitable point with the insulator joining ring 63, the housing 5 (as anode-side current collector) can be welded to the metallic anode closure part 64 after the joining process and thus the hermetically sealed anode space 41 is formed. If a carbon felt 23 has been introduced into the current collector 1, the preferably one-step joining or the high-temperature soldering process can only take place with the exclusion of oxygen, since otherwise the carbon is oxidized. Following the welding processes associated with the one-step joining, the electrochemical cell has only a single opening, namely the open pipe end of the filler pipe 13 of the cathode-side current collector 1, or in the case of several current collectors 1, 1 ', a plurality of openings. The granulate mixture of the cathode 2 is introduced into the cathode space 21 of the electrochemical cell via this opening of the filling pipe 13. With the exclusion of oxygen and water, e.g. B. under vacuum or by flushing with inert gas, the secondary electrolyte 22 is then introduced in liquid form through the same opening of the filler tube 13 into the cathode compartment 21 of the cell. Finally, the opening of the cell - z. B. with a deep-drawn part or a sheet metal blank 62 to close the upper pipe end of the filler pipe 13 - welded to the protruding end of the current collector 1.

In a further embodiment of the final cell assembly, which is shown schematically in Fig. 6 and 7, the filler pipe 13 of the current collector 1 is so far from the Cathode closure part 61 shows that it is squeezed off outside the completely filled cell and the narrow end face that is formed can be welded shut directly.

A further modification of the current collector 1 is shown in FIGS. 6 and 7, which is used to introduce the carbon felt 23 into the metal tube 11 after it has been pressed. For this purpose, after the pressed pipe section 12 has been produced, a pinch edge 16 is opened, for example by cutting or milling, so that a strip-shaped carbon felt 23 can be introduced through the pinch edge 17 removed from the side.

Another embodiment of the current collector 1 is shown in FIGS. In this embodiment, to increase the surface area of the metal tube 11 (only designated in FIG. 1), the pressed tube section 12 of the current collector 1 has been pressed in in four radial directions to the central axis 51, two directions of which are collinearly oppositely aligned. As a result, the cross section of the pressed pipe section 12 is star-shaped, as can be seen in FIG. 9.

As a further alternative cross-section, the star shape can also be three-, five-, six-pointed, etc. (not shown). Although not shown in FIG. 8, through holes 14 with metal tufts 15 or slots with metal sheets, as shown in FIG. 11, can additionally be introduced in this example in order to further enlarge the surface.

A further modification for producing a star-shaped cross section of the pressed pipe section 12, which is shown in FIG. 10, can be carried out in such a way that initially a metal pipe

11 is produced in a star shape, as can be seen in FIG. 9, and then the unpressed pipe section is welded onto the pressed pipe section 12 as a filler pipe 13. This automatically creates four through holes 14 for filling the cathode granulate by means of the different cross-sectional shapes of the pressed pipe section 12 and the cylindrical filling pipe 13 and in this case do not have to be punched. In order to prevent Ni / NaCl granules from penetrating into the interior of the pressed pipe section 12, the upper pressed area and the lower opening of the current collector 1 can be made with a sufficiently small gap or a carbon felt 23 can be inserted for sealing.

In a further embodiment of the current collector 1, which is advantageously positioned axially in the cathode compartment 21 in accordance with the exemplary embodiment shown in FIG. 11, a tubular base body (metal tube 11) made of an electrically highly conductive metal is inserted into a lower pressed pipe section 12 and an upper unpressed one to fill the cathode compartment 21 Pipe section, the filler pipe 13, divided. Through the pressed pipe section

12, the cathode 2 can only be filled into the cathode space 21 via a through hole 14 without reaching the secondary electrolyte reservoir 24 in the interior of the metal tube 11. Through slots in the metal pipe 11 below the pressed pipe section 12, fins 18 made of embedded metal sheets can also be inserted, which are welded, pressed or soldered to the metal pipe 11. The fins 18 can go through, individually attached or reshaped in such a way that a sheet metal is adapted in the interior of the contour of the metal tube 11 and thus forms at least two fins 18.

In a further embodiment according to FIG. 12, the fins 18 can also be formed only by a sheet metal 19 that is folded in a meander shape.

As can be seen in FIG. 12, a star-shaped or corrugated cross-sectional contour of the secondary electrolyte reservoir 24 can also be formed from a folded sheet metal 19, which is then welded, soldered to the metal tube 11 of the current collector 1, which is divided into the open filler pipe 13 and the pressed pipe section 12 or is pressed. For this purpose, the folded sheet 19 can only be made with fin-like structures and then to an inside z. B. bent as a tubular structure and connected to a fin 18. Instead of one folded sheet 19, several folded sheets 19 can also be used for shaping. The gap dimensions between the fins 18 formed must be small enough that no cathode 2 can penetrate into the secondary electrolyte reservoir 24. Even in the event that the internal dimensions of the resulting star-shaped cross-sectional contour are smaller or larger than the lower opening of the metal tube 11, the secondary electrolyte reservoir 24 must nevertheless remain free of granules from the cathode 2 and the remaining openings must, for. B. be closed sufficiently tightly by further pressing at least the lower end of the metal tube 11 or one or more carbon felts 23 must be introduced.

13 shows a further measure for increasing the power of the electrochemical cell, which is designed as a radial double cell. Another current collector 1 'is provided for contacting a further cathode 2' in the space between the housing 5 and the outer wall of a double-walled separator 3 in this example, which contains the anode space 41 for the anode 4 in a cylindrical annular gap. The current collector 1 ', which is advantageously used in addition to the current collector 1 positioned in the central axis 51 as an unpressed metal tube 11 (not shown in FIG. 13), also enables the substitution of the carbon felt 23 by placing the secondary electrolyte reservoir 24' between the Current collector 1 'and the inner wall of the housing 5 is formed, while at the same time a direct contact of the granules of the further cathode 2' to the housing wall is prevented, but the electrical contact takes place via the current collector 1 ', whereby the electrochemical corrosion requirement on the actual housing 5 is reduced. Equally meaning, the surface of the further current collector 1 'can also be increased further by either adding additional folded metal sheets 19 oriented towards the central axis 51 or the sheet metal strips themselves have a construction similar to the housing contour and fins oriented towards the central axis 51 18 train. Here, when using the additional current collector 1 ', made z. B. as a metal tube 11 made of nickel or, depending on the cell chemistry, also made of nickel-plated copper, with a diameter smaller than the inner diameter of the housing 5, the further secondary electrolyte reservoir 24 'can be created so that at the same time the electrochemically active cathode 2' is electrically contacted and a carbon felt 23 above the filling level of the cathode 2 'can be dispensed with. A further carbon felt 23 ′ positioned in the bottom area of the housing 5 prevents direct contact between the granules of the cathode 2 and the wall of the housing 5. The further current collector 1 'positioned in the outer area of the further cathode space 21' can instead of a tube flanged at the bottom also be formed by sheet metal strips bent in the bottom area of the housing 5 by being directly connected to the bottom of the housing 5, which is either a separate from the housing 5 Is a component or was made by deep-drawing the housing 5 in one piece, is connected (z. B. spot welding, soldering). In order to further reduce the contact resistance of the further current collector 1 'to the housing 5, the individual sheet metal strips of the further current collector T can be made to an excess length so that they are additionally bent over and then enable further, flat contact with the inner wall of the housing 5 (not visible in the drawing). Alternatively, the current collector T can be welded in the upper closure area of the cell to the housing 5 or other parts of the closure area. For the pantograph 1, all variants, as described above, remain possible. However, the designs of FIGS. 11 and 12 can preferably be used.

With the invention, a particularly inexpensive electrochemical cell is assembled from a few parts that are easy to manufacture and assemble. In particular, the novel shape of the current collector 1 enables simple and effective filling of the cell with the metal granules of the cathode 2 and the secondary electrolyte 22 after the cell has already been fully assembled and hermetically welded. The possibility of producing the current collector 1 monolithically and of enabling the contacting from one cell to the next directly with the pressed and welded filler pipe 13 eliminates the need for joining processes and the contact resistance can also be reduced. Since the current collector 1 is inaccessible to the Ni / NaCl granules in a separate internal volume, but can be easily infiltrated by the secondary electrolyte 22, the function of the carbon felt 23 as a secondary electrolyte reservoir 24 can be substituted. Furthermore, with the special type of surface enlargement of the current collector 1, a more uniform radial current distribution in the cathode chamber 21 is achieved. List of reference symbols

1, 1 '(cathode-side) pantograph

11 metal tube

12 pressed pipe section

13 Filler pipe / unpressed pipe section

14 punching / through hole

15 tufts of metal (made of metal strips or wires)

16 pinch edge

17 worn pinch edge

18 fin

19 folded sheet metal

2, 2 'cathode

21, 21 'cathode compartment

22 secondary electrolyte

23.23 ’(carbon) felt

24, 24 '(secondary electrolyte) reservoir

3 separator (solid primary electrolyte)

4 anode

41 anode compartment

5 housing

51 central axis

6 cell closure

61 (metallic) cathode closure part

62 round sheet metal

63 (ceramic) insulator retaining ring

64 Anode cap

Claims

1. Electrochemical sodium metal halide cell, comprising a housing (5) with a central axis (51), a separator (3) which is expanded equidistantly from the housing (5) around the central axis (51) of the housing (5) and is used as a solid primary electrolyte separates an anode compartment (41) from a cathode compartment (21) in an electrically insulating manner and hermetically, but is permeable to sodium ions, a cathode (2) filling the cathode compartment (21) and made of a porous mixture of metal powder and metal halide powder granules and a Cathode compartment (21) and the porous mixture of the cathode (2) impregnating secondary electrolyte (22) from a sodium-metal halide molten salt and a metallic cathode-side current collector (1) in the cathode compartment (21) elongated around the central axis (51), thereby marked that

- The current collector (1) is a metal tube (11) with a high electrical conductivity of s> 10 ⁶ S / m, which is contained in the porous mixture of granules of the cathode (2) and in the secondary electrolyte (22) in the separator (3) is immersed and designed as a pressed pipe section (12) so narrowed on the inside that no granules of the cathode (2), but only secondary electrolyte (22) can penetrate, and to the outside with elements for surface enlargement (15, 16, 18, 19) of the Pantograph (1) is provided, and

- The current collector (1) above the immersed, pressed pipe section (12) has an unpressed pipe section as a filler pipe (13) for filling the cathode space (21), at a transition from the pressed pipe section (12) to the unpressed pipe section of the filler pipe (13) there is at least one through hole (14) opening outwards, so that the filling tube (13) for filling the porous mixture of granules of the cathode (2) into the cathode space (21) is only outside the pressed tube section (12) and can be used to fill the entire cathode space (21) with secondary electrolyte (22).

2. Electrochemical cell according to claim 1, characterized in that the current collector (1) in the pressed pipe section (12) has a carbon felt (23) which was inserted into the pressed pipe section (12) before pressing.

3. Electrochemical cell according to claim 1, characterized in that the current collector (1) in the pressed pipe section (12) has a carbon felt (23) which after pressing and removal of a pinch edge (16) of the pressed pipe section (12) in the pressed pipe section (12) can be pushed in laterally.

4. Electrochemical cell according to one of claims 1 to 3, characterized in that the current collector (1) in the pressed pipe section (12) has punchings in the form of further through holes (14).

5. Electrochemical cell according to claim 4, characterized in that the current collector (1) in the pressed pipe section (12) in the through holes (14) fastened metal tufts (15) of metal strips or wires from a not by the electrochemical processes of the cell attacked metal with comparable high conductivity as the metal tube (11) of the current collector (1).

6. Electrochemical cell according to one of claims 1 to 5, characterized in that a commercially available nickel, aluminum or copper pipe is used as the current collector (1).

7. Electrochemical cell according to claim 1, characterized in that on the current collector (1) the elements for surface enlargement with at least one element from the group of punched through holes (14) or other relief-forming structures with pinch edges (16), metal tufts (15), Fins (18) or folded sheets (19) are formed.

8. Electrochemical cell according to one of claims 5 to 7, characterized in that the metal tufts (15) are made of metal strips or wires made of nickel or molybdenum.

9. Electrochemical cell according to one of claims 5 to 7, characterized in that the metal tufts (15) of metal strips or wires are aligned so that local resistance gradients in the cathode compartment (21) are minimized or evenly distributed over the cross section of the cathode compartment (21) are.

10. Electrochemical cell according to one of claims 5 to 7, characterized in that the metal strips or wires used in the metal tufts (15) have a length which is selected to be smaller, the higher the cell capacities are to be achieved, and the larger up to a maximum of the separator (3) is selected, the higher the capacity to be removed from the cell.

11. Electrochemical cell according to one of claims 1 to 10, characterized in that the unpressed pipe section of the filler pipe (13) of the current collector (1) after filling the porous mixture of the cathode (2) and the secondary electrolyte (22) with a material fit Sheet metal blank (62) or a deep-drawn part is closed.

12. Electrochemical cell according to one of claims 1 to 10, characterized in that the unpressed tube section of the filler tube (13) of the current collector (1) after filling the porous mixture of the cathode (2) and the secondary electrolyte (22) at the upper end of the tube Filler pipe (13) is squeezed or hermetically sealed with a soldered or welded seam.

13. Electrochemical cell according to one of claims 1 to 12, characterized in that the pressed tube section (12) of the current collector (1) is pressed flat from two collinear directions.

14. Arrangement according to one of claims 1 to 12, characterized in that the pressed pipe section (12) of the current collector (1) is pressed from at least three evenly distributed directions offset around the central axis (51) to form a star-shaped cross section.

15. Electrochemical cell according to one of claims 13 to 14, characterized in that the pressed pipe section (12) of the current collector (1) is pressed by the effects of force in such a way that an interior space that is formed as a secondary electrolyte reservoir (24) is just large enough how a volume of the secondary electrolyte (22), which is necessary in the fully charged state of the cell for the complete wetting of the current collector (1), is kept available.

16. Electrochemical cell according to one of claims 1 to 12, characterized in that below the pressed tube section (12) of the current collector (1) a metal tube (11) is attached which is occupied by radial fins (18) which are tangentially equidistant Slots of the metal tube (11) are inserted.

17. Electrochemical cell according to one of claims 1 to 12, characterized in that below the pressed pipe section (12) of the current collector (1) a metal pipe (11) with radial fins (18) is attached, which consists of an equidistantly folded sheet metal (19 ) and its axially symmetrical bend is generated.

18. A method of manufacturing a sodium metal halide electrochemical cell comprising the steps:

- Provision of a housing (5) to form an anode space (41), a separator (3) that can be used equidistantly to the housing (5) as an electrically insulating solid primary electrolyte that is only permeable to sodium ions for separating the anode space (41) from a cathode space ( 21), a cathode (2) made of a porous mixture of metal powder and metal halide granules and a secondary electrolyte (22) for soaking the porous mixture of the cathode (2),

- Manufacture of a cathode-side current collector (1) from a metal tube (11) which is formed into a compressed pipe section (12) current collector (1) by forces acting radially on a central axis (51) and with an unpressed pipe section at the upper end remains as a filler pipe (13), at least one through-hole (14) being made at a transition from the pressed pipe section (12) to the filler pipe (13), which is provided as an outlet opening of the filler pipe (13) for filling the cathode space (21), - Production of a cell closure (6) from a cathode closure part (61) with a central opening for the implementation of the filler pipe (13) of the current collector (1) in the central opening of the cathode closure part (61) and material connection of the cathode closure part (61) with an insulator support ring ( 63) and materially joining an anode closure part (64) to the insulator joining ring (63),

- Positioning of the current collector (1) collinear with the central axis (51) in the separator (3) as well as the housing (5) arranged equidistantly around the separator (3) by means of the cell closure (6) made of insulator joining ring (63) and anode closure part ( 64) through a one-step joining process as well as material connection of the joints,

- Filling the porous mixture of metal powder and metal halide powder granules of the cathode (2) through the filler tube (13) of the current collector (1) and the at least one through hole (14) of the filler tube (13) into the cathode space (21) in the separator ( 3) only outside the current collector (1) and subsequent pouring of the secondary electrolyte (22) in liquid form with the exclusion of oxygen and

- Final hermetic sealing of the electrochemical cell by materially closing the filler pipe (13).

19. The method according to claim 18, wherein during the manufacture of the cell closure (6) from the cathode closure part (61) and the cohesively connected cathode closure part (61) with insulator joining ring (63) and attached anode closure part (64) of the current collector (1) in the central opening of the Cathode closure part (61) is firmly fixed before the positioning of the current collector (1) in the separator (3) as well as in the arranged housing (5) collinear with the central axis (51) by the cell closure (6) made of insulator joining ring (63) and anode closure part ( 64) takes place through the one-step joining process as well as a material connection of the joints.

20. The method according to claim 18, wherein when producing the cell closure (6) from the cathode closure part (61) and the cohesively connected cathode closure part (61) with insulator joining ring (63) and attached anode closure part (64) of the current collector (1) in the central opening of the Cathode closure part (61) is positioned and after positioning the current collector (1) collinearly in the separator (3) and in the housing (5), which is equidistant around the separator (3) and collinearly with the central axis (51), through the Step-joining process is fixed by means of the cell closure (6) consisting of insulator joining ring (63) and anode closure part (64) by materially connecting the joints.

21. The method according to claim 18, wherein during the production of the cell closure (6) from the cathode closure part (61) and the materially connected cathode closure part (61) with insulator joining ring (63) and attached anode closure part (64) the current collector (1) is firmly fixed in the central opening of the cathode closure part (61) before the current collector (1) is positioned in the separator (3) collinear with the central axis (51) through the cell closure (6) made of insulator joining ring (63) and anode closure part (64) by the one-step joining process and then the housing (5) arranged equidistant to the separator (3) and collinear to the central axis (51) and the joints are fixed by a material bond.

22. The method according to any one of claims 18 to 21, wherein elements for increasing the surface area of the current collector (1) are introduced equidistantly into the pressed pipe section (12) in the form of through holes (14).

23. The method according to claim 22, wherein metal tufts (15) made of metal strips or wire are inserted into the through holes (14) in the pressed pipe section (12).

24. The method according to any one of claims 18 to 23, wherein the pressed pipe section (12) of the current collector (1) is formed flat by collinear radial force.

25. The method according to any one of claims 18 to 23, wherein the pressed pipe section (12) of the current collector (1) is formed in a star shape by a plurality of radial forces uniformly distributed around the central axis (51).

26. The method according to any one of claims 18 to 21, wherein to increase the surface area of the current collector (1) below the pressed pipe section (12) on a metal pipe (11) radial fins (18) are attached, which are inserted into tangentially equidistant slots.

27. The method according to any one of claims 18 to 21, wherein to increase the surface area of the current collector (1) below the pressed pipe section (12) on a metal pipe (11) radial fins (18) are produced by a folded sheet metal (19).

28. The method according to any one of claims 18 to 27, wherein the closing of the filler pipe (13) is carried out by welding or soldering the upper end of the pipe to a sheet metal blank (62).

29. The method according to any one of claims 18 to 27, wherein the closing of the filler pipe (13) takes place by squeezing the upper end of the tube and then welding or soldering the squeezed upper end of the tube.