Method and system for producing a composite consisting of an electric arrester and at least one electrode, composite consisting of an electric arrester and at least one electrode, and battery cell

Abstract

The invention relates to a method and a system for producing a composite consisting of an electric arrester and at least one electrode. The invention additionally relates to such a composite and to a battery cell comprising such a composite. The method is characterized in that a laser beam is emitted onto at least one part of the contact surface between a joint region of at least one electrode and a joint region of a metal electric arrester such that the metal of the joint region of the at least one electrode and the metal of the joint region of the electric arrester are heated in said part of the contact surface to a temperature which equals at least 180 °C. A composite can be economically provided which allows high electric currents in the joint region.

Description

[0001] Method and system for producing a composite comprising an electrical conductor and at least one electrode, a composite comprising an electrical conductor and at least one electrode, and a battery cell. A method and a system for producing a composite comprising an electrical conductor and at least one electrode are presented. Furthermore, such a composite and a battery cell with such a composite are provided. The method is characterized in that a laser beam is irradiated at least onto a part of a contact surface between a joining region of at least one electrode and a

[0002] Joining area of ​​a metallic electrical conductor, so that the metal of the joining area of ​​the at least one electrode and the metal of the joining area of ​​the electrical conductor in this part of the contact surface are heated to a temperature of at least 180°C. A composite can be provided in an economical manner which has high electrical

[0003] Currents in the joining area are permitted. A lithium-sulfur pouch cell consists, among other things, of several (1-50) lithium anodes, which must be joined to the negative terminal of the battery cell using a current collector contact (nickel or nickel-plated copper tab).

[0004] Lithium metal is highly reactive and stable only in a dry atmosphere. Therefore, lithium metal processing takes place primarily in dry air (dew point < -40°C) or under protective gas atmospheres. Furthermore, it is known that lithium can react with the oxygen, nitrogen, and water present in air (e.g., to form lithium oxide, lithium nitride, and lithium hydroxide). Therefore, lithium metal foils always have a thin protective or passivation layer containing or consisting of lithium compounds (such as lithium oxide, lithium nitride, and lithium hydroxide).

[0005] The creation of a direct joint between several layers of lithium foil (foil thickness: 30-100 μm) and the current collector contact has not yet been implemented due to the high ductility and reactivity of lithium and its low melting temperature of approximately 180°C. Instead, the anodes were manufactured from two lithium foils and a copper tab sandwiched between them, allowing the use of established joining processes. The additional effort required to manufacture such a composite anode, as well as the additional weight of a copper tab, can be eliminated by a direct lithium-nickel joint. In addition, a direct joint between the lithium anode and the current collector contact achieves a lower and long-term stable contact resistance.

[0006] Lithium anodes have traditionally been made from two layers of lithium foil with a copper tab sandwiched between them. It is known to then join the individual copper tabs to a current collector contact using ultrasonic welding.

[0007] EP 2 791 998 B1 discloses a method in which lithium anodes are joined directly to a current collector contact using ultrasound. However, this joining process has the disadvantage that reliable joining is no longer possible with a large number of lithium anode layers. Furthermore, the ultrasound-based method has the disadvantage that high pressure must be exerted on the stack during joining. The high pressure causes liquid lithium to escape at the side edges of the stack, whereby the layer thickness of the individual stacked lithium anodes becomes thinner, particularly at the side edges, and the maximum possible electrical current is reduced there. In addition, the high pressure during ultrasonic welding deforms the metallic current collector so that it is no longer planar, which reduces the maximum possible electrical current.In addition, ultrasonic vibration can cause the joining surfaces to tear, increasing the scrap rate. Furthermore, the joining tools used in ultrasonic welding are subject to mechanical wear, which can make the process costly.

[0008] Based on this, it was the object of the present invention to provide a method and a system with which a composite comprising an electrical arrester and at least one electrode can be produced, which overcomes or no longer has at least one disadvantage of the prior art. Furthermore, a corresponding composite comprising an electrical arrester and at least one electrode should be provided. In addition, a battery cell with advantageous properties should be provided. In particular, the method and the system should provide a composite comprising an electrical arrester and at least one electrode as well as a battery cell in the most economical manner possible (low risk of scrap and wear of tools).

[0009] The object is achieved by the method having the features of claim 1, the system having the features of claim 8, the electrode having the features of claim 15 and the battery having the features of claim 18.

[0010] According to the invention, a method for producing a composite from an electrical conductor and at least one electrode is presented, comprising the following steps: a) providing at least one electrode which consists of a metal selected from the group consisting of lithium, lithium alloy and combinations thereof, wherein the at least one electrode has a flat joining region with a top side and a bottom side; b) providing an electrical conductor which has a flat joining region with a top side and a bottom side, wherein the flat joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel and combinations and alloys thereof;c) arranging the underside of the planar joining region of the at least one electrode on the top side of the planar joining region of the electrical conductor, whereby a contact surface is created between the underside of the planar joining region of the at least one electrode and the top side of the planar joining region of the electrical conductor; characterized in that the method further comprises irradiating a laser beam through the joining region of the at least one electrode onto at least a portion of the contact surface, so that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor are heated in the portion of the contact surface to a temperature of at least 180°C (preferably at least the melting point of the metal of the electrode or the joining region thereof).

[0011] In the method, the joining area of ​​the at least one electrode is melted by the laser beam, and in the area of ​​the laser beam, a local vapor capillary forms within the electrode melt, in the joining area of ​​the at least one electrode. The surrounding lithium melt is displaced by the vapor capillary, allowing the laser beam to penetrate to the joining area of ​​the electrical conductor (i.e., to the current collector tab) and act directly there. The laser beam and the surrounding electrode melt (e.g., lithium melt in the case of an electrode made of lithium) locally heat the joining area of ​​the electrical conductor to temperatures of at least 180°C, i.e., to a temperature that corresponds at least to the melting point of lithium. This forms an electrode melt pool (e.g., lithium melt pool) around the irradiated area.

[0012] Due to the local temperature increase in the joining area of ​​the electrical arrester, local wetting of the joining area of ​​the electrical arrester with the at least one molten electrode (e.g. lithium) occurs and diffusion from the at least one molten electrode (e.g. lithium) into the surface structure (due to surface roughness) of the joining area of ​​the electrical arrester. This diffusion creates very close contact between the at least one electrode and the electrical arrester, which allows very high electrical currents to flow. With a suitable choice of electrical arrester, local formation of an alloy can also occur between the metal in the joining area of ​​the at least one electrode (e.g. lithium) and the metal in the joining area of ​​the electrical arrester (e.g. nickel). After the irradiation has ended, the local melt in the joining area of ​​the at least one electrode solidifies.

[0013] In the event that joining areas of several electrodes have been stacked on top of each other, the solidification of the electrode melt generated in the vapor capillary causes a local connection of the individual joining areas of the electrodes to one another.

[0014] The method according to the invention has the advantage that – unlike, for example, ultrasonic joining – a larger number of electrode layers (or electrode layers) can be connected in the joining area to the joining area of ​​the electrical conductor. Furthermore, the method according to the invention makes it possible to join the joining area of ​​the electrical conductor from both sides to the joining area of ​​the at least one electrode, whereby the maximum number of electrode layers in the joining area (e.g., lithium layers) can be further increased (i.e., doubled) compared to ultrasonic joining.

[0015] A further advantage of the method according to the invention is that, unlike ultrasonic joining, no mechanical deformation of the joining area of ​​the at least one electrode and the joining area of ​​the electrical conductor occurs (e.g., no seepage of liquid lithium from the edge region of the joining area, i.e., from the boundary line of the joining area). This increases the maximum possible electrical current that can flow between the joining area of ​​the at least one electrode and the joining area of ​​the electrical conductor. Furthermore, unlike ultrasonic joining, tearing of the joining surfaces can be avoided, which reduces scrap and makes the process more economical.

[0016] In addition, the method according to the invention has the advantage that the heat input can be controlled locally and a minimum required heat input can be selected.

[0017] A further advantage of the method according to the invention is that no additional materials are required for the joining process (such as an additional plastic film during ultrasonic welding to protect the anvil from contamination). This also means that when installing the manufactured composite consisting of an electrical conductor and at least one electrode, the manufactured composite (and also a battery cell with said composite) can be free of a plastic film, which offers advantages in terms of the overall weight of the composite (and the battery cell).

[0018] The method according to the invention also has the advantage that the process duration is shorter than with ultrasonic joining.

[0019] An additional advantage of the method according to the invention is that, in contrast to ultrasonic joining, the joining area can be very small (limitation of the area only by the diameter of the laser beam), whereby even small joining areas of electrical arresters can be joined with the at least one electrode.

[0020] In an optional embodiment of the method according to the invention, part of the heating of the joining region (e.g. heating up to 170 °C) takes place via induction heating and the remaining heating to the required temperature of at least 180 °C takes place locally by the laser beam (e.g. heating from 170 °C to at least 180 °C, i.e. by the remaining > 10 K). If, in the method according to the invention, the metal of the joining region of the at least one electrode (i.e. the lithium, the lithium alloy or a combination thereof) and the metal of the joining region of the electrical conductor in that part of the contact surface are heated to a temperature of at least 180 °C, a protective layer or passivation layer that was present on the metal of the joining region of the at least one electrode before joining is destroyed. In the process, new, highly reactive interfaces are formed.In order to prevent a reaction of these newly forming interfaces with air components (oxygen, nitrogen and water vapor) at the joining temperature, it is advantageous in the method according to the invention to apply a noble gas (such as argon or helium) to the joining area during the joining process.

[0021] In a preferred embodiment, the method according to the invention therefore comprises exposing the joining area to at least one noble gas (such as argon or helium).

[0022] Furthermore, the method may include, after cooling the joining area to room temperature (e.g., in a dry air atmosphere, < -40 °C dew point), producing a protective layer or passivation layer on the edge regions of the joining area. In this case, the method may include exposing the edge region of the joining area to a gas from the gas source (e.g., containing oxygen, nitrogen, and / or water vapor).

[0023] The planar joining region of the at least one electrode can have a thickness in the range of n times from 40 to 140 pm (thickness of a planar joining region of an individual electrode), where n is an integer of at least 30, preferably at least 50, more preferably at least 60, most preferably at least 65, in particular at least 70, wherein the thickness relates to an extent of the joining region perpendicular to its upper side. Greater thicknesses are advantageous since more planar joining regions can be joined to the planar joining region of the conductor. The planar joining region of the electrical conductor can have a thickness in the range of 50 to 400 μm, preferably in the range of 100 to 350 μm, more preferably in the range of 200 to 350 nm, wherein the thickness relates to an extent of the joining region perpendicular to its upper side.

[0024] In the method, the contact surface can be defined by an (imaginary) boundary line (i.e., by a line defining the edge of the contact surface), wherein the laser beam is radiated through the joining region of the at least one electrode only onto a portion of the contact surface that is at a specific distance from the boundary line of the contact surface. This embodiment can ensure that the metal of the joining region of the electrode (e.g., lithium) does not melt in the edge region of the contact surface, thereby preventing liquid metal (e.g., lithium) from escaping from the edge of the contact surface and locally reducing the height of the joining region of the electrode due to the escape of the metal.

[0025] Furthermore, in the method, the contact surface can have a length in a longitudinal direction along the contact surface in the range of 0.5 to 20 mm, preferably 1 to 10 mm.

[0026] Furthermore, in the method, the contact surface may have a width in a transverse direction along the contact surface in the range of 0.5 to 6, preferably 1 to 3 mm.

[0027] The laser beam used in the method can be irradiated in such a way that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor are heated to a temperature of at least 190 °C, preferably at least 200 °C, particularly preferably at least 210 °C, in particular at least 220 °C. A temperature of at least 210 °C, particularly at least 220 °C, has proven particularly advantageous for effective wetting of the joining region of the electrical conductor with the metal of the joining region of the at least one electrode (e.g., lithium).Furthermore, the laser beam used in the process can have a wavelength in the UV range, VIS range or IR range, preferably a wavelength in the NIR range, particularly preferably a wavelength in the range from 800 to 1400 nm, very particularly preferably a wavelength in the range from 1000 to 1100 nm, in particular a wavelength in the range of 1065 nm.

[0028] In addition, the laser beam used in the process can have a laser power in a range of 200 to 2000 watts, preferably 300 to 1500 watts, particularly preferably 400 to 1000 W, in particular 500 to 700 watts.

[0029] In addition, the laser beam used in the process can have a focal length in the range of 50 to 500 mm, preferably in the range of 100 to 400 mm, particularly preferably in the range of 150 to 350 mm, very particularly preferably in the range of 200 to 300 mm, in particular 250 mm.

[0030] Apart from that, the laser beam used in the method can be irradiated onto a part of the contact surface which constitutes >0% to 90%, preferably 2% to 70%, particularly preferably 4% to 50%, very particularly preferably 6% to 30%, in particular 8% to 20%, optionally 10% to 15%, of a total area of ​​the contact surface.

[0031] In a preferred embodiment of the method, the laser beam is focused onto a focal point on the contact surface. The focal point onto which the laser beam is focused can have a diameter in the range of 10 to 200 pm, preferably in the range of 20 to 150 pm, particularly preferably in the range of 30 to 100 pm, most preferably in the range of 40 to 50 pm, in particular 45 pm.

[0032] Furthermore, the focal point onto which the laser beam is focused can be moved along the contact surface at a speed in the range of 0.1 to 5 m / sec., preferably in the range of 0.2 to 4 m / sec., particularly preferably in the range of 0.3 to 3.5 m / sec., most particularly preferably in the range of 0.4 to 3 m / sec., optionally in the range of 0.5 to 2 m / sec.

[0033] In addition, the focal point onto which the laser beam is focused can be moved in a pattern along the contact surface, wherein the pattern is selected from the group consisting of circular pattern, elliptical pattern, line-shaped pattern, zigzag pattern and combinations thereof, wherein preferably at least two lines of the zigzag pattern, optionally several lines of the zigzag pattern, are arranged at an angle in the range of 20 to 40°, in particular 30°, to one another.

[0034] Furthermore, the focal point on which the laser beam is focused can be moved at a distance of at least 1 mm, preferably at least 2 mm, from a boundary line of the contact surface (i.e., a line defining the edge of the contact surface). A distance in these ranges is advantageous because it can ensure that no liquid metal leaks out at the edges of the assembly during joining.

[0035] In step a) of the method, at least 29, preferably at least 49, particularly preferably at least 59, very particularly preferably at least 64, in particular at least 69, further electrodes can be provided, each consisting of a metal selected from the group consisting of lithium, lithium alloy and combinations thereof, and each having a flat joining region with a top side and a bottom side.

[0036] In step c) of the method, the planar joining region of each further electrode can be arranged on the planar joining region of the at least one electrode, and in step d) the laser beam can be irradiated through all planar joining regions of the electrodes onto at least a part of the contact surface, so that the metal of all planar joining regions of the electrodes and the metal of the planar joining region of the electrical conductor in the part of the contact surface is heated to a temperature of at least 180°C (preferably at least to the melting temperature of the metal of the electrode).

[0037] Alternatively, in step c) of the method, an upper side of a planar joining region of a single one of the further electrodes can be arranged on the underside of the planar joining region of the electrical conductor, wherein a further contact surface is created between the upper side of the planar joining region of the single one of the further electrodes and the underside of the planar joining region of the electrical conductor, wherein the planar joining regions of the other further planar electrodes are arranged at least partially or completely on the planar joining region of the at least one electrode and / or on the planar joining region of the single one of the further electrodes, and in step d) the laser beam is irradiated through all planar joining regions of the electrodes at least onto a part of the contact surface and at least onto a part of the further contact surface,so that the metal of the flat joining areas of all electrodes and the metal of the flat joining area of ​​the electrical conductor in the part of the contact surface and the part of the further contact surface are heated to a temperature of at least 180°C (preferably at least to the melting temperature of the metal of the electrode).

[0038] According to the invention, a system for producing a composite of an electrical conductor and at least one electrode is further provided, comprising: a) at least one electrode consisting of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, wherein the at least one electrode has a planar joining region with a top side and a bottom side; and b) an electrical conductor having a planar joining region with a top side and a bottom side, wherein the planar joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel, and combinations and alloys thereof;wherein the underside of the planar joining region of the at least one electrode is arranged on the top side of the planar joining region of the electrical conductor, and a contact surface exists between the underside of the planar joining region of the at least one electrode and the top side of the planar joining region of the electrical conductor; characterized in that the system contains a laser configured to radiate a laser beam through the planar joining region of the at least one electrode onto at least a portion of the contact surface, such that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor in the portion of the contact surface are heated to a temperature of at least 180°C (preferably at least to the melting point of the metal of the electrode).

[0039] The advantages of the method according to the invention also apply to the system according to the invention.

[0040] In an optional embodiment of the system according to the invention, the system has an induction heater and the system is configured, optionally controlled by a control unit of the system, to heat a part of the joining area (e.g. heating up to 170 °C) via the induction heater and to heat it locally to the required temperature of at least 180 °C by the laser beam (e.g. heating from 170 °C to at least 180 °C, ie by the remaining > 10 K).

[0041] In a preferred embodiment, the system according to the invention comprises at least one noble gas source, and the system is configured to apply at least one noble gas from the at least one noble gas source to the joining area. The noble gas can be, for example, argon or helium. Preferably, a control unit of the system is configured to initiate said application.

[0042] Furthermore, the system can have a gas source, wherein the gas source preferably contains a gas that contains or consists of proportions of oxygen, nitrogen and / or water vapor. The gas is preferably air. The system can be configured to produce a protective layer or passivation layer on edge regions of the joining region after the joining region has cooled to room temperature (e.g. in a dry air atmosphere, < -40 °C dew point). In this case, the system can be configured to subject the edge region of the joining region to a gas from the gas source (e.g. with proportions of oxygen, nitrogen and / or water vapor). Preferably, a control unit of the system is configured to initiate said exposure.

[0043] The planar joining region of the at least one electrode of the system can have a thickness in the range of n times from 40 to 140 pm, where n is an integer of at least 30, preferably at least 50, particularly preferably at least 60, very particularly preferably at least 65, in particular at least 70, where the thickness refers to an extension of the joining region perpendicular to its upper side.

[0044] The planar joining region of the electrical conductor of the system can have a thickness in the range of 50 to 400 µm, preferably in the range of 100 to 350 µm, particularly preferably in the range of 200 to 350 nm, wherein the thickness refers to an extension of the joining region perpendicular to its upper side.

[0045] The contact surface can be defined by an (imaginary) boundary line, wherein the laser of the system is configured to radiate the laser beam through the joining region of the at least one electrode only onto a part of the contact surface which has a certain distance from the boundary line of the contact surface.

[0046] The contact surface may have a length in a longitudinal direction along the contact surface in the range of 0.5 to 20 mm, preferably 1 to 10 mm.

[0047] Furthermore, the contact surface can have a width in a transverse direction along the contact surface in the range of 0.5 to 6, preferably 1 to 3 mm.

[0048] The system may comprise a control unit configured to control or regulate at least the laser.

[0049] The laser of the system can be configured, optionally controlled via a control unit of the system, to irradiate the laser beam in such a way that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor are heated to a temperature which is at least 190 °C, preferably at least 200 °C, particularly preferably at least 210 °C, in particular at least 220 °C.

[0050] Furthermore, the laser of the system can be configured, optionally controlled via a control unit of the system, to irradiate the laser beam with a wavelength in the UV range, VIS range or IR range, preferably with a wavelength in the NI R range, particularly preferably with a wavelength in the range of 800 to 1400 nm, very particularly preferably with a wavelength in the range of 1000 to 1100 nm, in particular with a wavelength in the range of 1065 nm.

[0051] In addition, the laser of the system can be configured, optionally controlled via a control unit of the system, to irradiate the laser beam with a laser power in a range of 200 to 2000 watts, preferably 300 to 1500 watts, particularly preferably 400 to 1000 W, in particular 500 to 700 watts.

[0052] Apart from that, the laser of the system can be configured, optionally controlled via a control unit of the system, to irradiate the laser beam with a focal length in the range of 50 to 500 mm, preferably in the range of 100 to 400 mm, particularly preferably in the range of 150 to 350 mm, very particularly preferably in the range of 200 to 300 mm, in particular 250 mm.

[0053] Furthermore, the laser of the system can be configured, optionally controlled via a control unit of the system, to irradiate the laser beam onto a part of the contact surface which makes up >0% to 90%, preferably 2% to 70%, particularly preferably 4% to 50%, very particularly preferably 6% to 30%, in particular 8% to 20%, optionally 10% to 15%, of a total area of ​​the contact surface.

[0054] In a preferred embodiment, the laser of the system is configured, optionally controlled via a control unit of the system, to focus the laser beam onto a focal point on the contact surface.

[0055] The laser of the system can be configured, optionally controlled via a control unit of the system, to adjust the focal point so that it has a diameter in the range of 10 to 200 pm, preferably in the range of 20 to 150 pm, particularly preferably in the range of 30 to 100 pm, very particularly preferably in the range of 40 to 50 pm, in particular 45 pm.

[0056] Furthermore, the laser of the system can be configured, optionally controlled via a control unit of the system, to move the focal point along the contact surface at a speed in the range of 0.1 to 5 m / sec., preferably in the range of 0.2 to 4 m / sec., particularly preferably in the range of 0.3 to 3.5 m / sec., most particularly preferably in the range of 0.4 to 3 m / sec., optionally in the range of 0.5 to 2 m / sec.

[0057] In addition, the laser of the system can be configured, optionally controlled via a control unit of the system, to move the focal point in a pattern along the contact surface, wherein the pattern is selected from the group consisting of circular pattern, elliptical pattern, line-shaped pattern and combinations thereof, wherein preferably at least two lines of the line-shaped pattern, optionally several lines of the line-shaped pattern, are arranged at an angle in the range of 20 to 40°, in particular 30°, to one another.

[0058] Apart from that, the laser of the system can be configured, optionally controlled via a control unit of the system, to move the focus point at a distance from a boundary line of the contact surface which is at least 1 mm, preferably at least 2 mm.

[0059] The system can contain at least 29, preferably at least 49, particularly preferably at least 59, very particularly preferably at least 64, in particular at least 69, further electrodes, each consisting of a metal selected from the group consisting of lithium, lithium alloy and combinations thereof, and each having a flat joining region with a top side and a bottom side.

[0060] The planar joining region of each additional electrode can be arranged on the planar joining region of the at least one electrode, and the laser can be configured, optionally controlled by a control unit of the system, to radiate the laser beam through all planar joining regions of the electrodes onto at least a portion of the contact surface, so that the metal of all planar joining regions of the electrodes and the metal of the planar joining region of the electrical conductor in the portion of the contact surface is heated to a temperature of at least 180°C (preferably at least to the melting temperature of the metal of the electrode). Alternatively, an upper side of a planar joining region of a single one of the additional electrodes can be arranged on the underside of the planar joining region of the electrical conductor.wherein a further contact surface exists between the upper side of the planar joining region of the only one of the further electrodes and the underside of the planar joining region of the electrical conductor, wherein the planar joining regions of the other further planar electrodes are arranged at least partially or completely on the planar joining region of the at least one electrode and / or on the planar joining region of the only one of the further electrodes, and the laser is configured, optionally controlled via a control unit of the system, to radiate the laser beam through all planar joining regions of the electrodes at least onto a part of the contact surface and at least onto a part of the further contact surface, so that the metal of the planar joining regions of all electrodes and the metal of the planar joining region of the electrical conductor are heated to a temperature in the part of the contact surface and in the part of the further contact surface,which is at least 180°C (preferably at least to the melting temperature of the metal of the electrode).

[0061] According to the invention, a composite of an electrical conductor and at least one electrode is further provided, containing or consisting of: a) at least one electrode consisting of a metal selected from the group consisting of lithium, lithium alloy and combinations thereof, wherein the at least one electrode has a planar joining region with a top side and a bottom side; b) an electrical conductor having a planar joining region with a top side and a bottom side, wherein the planar joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel and combinations and alloys thereof;wherein the joining region of the at least one electrode is arranged on the joining region of the planar electrical conductor and a contact surface exists between the two joining regions, characterized in that the metal of the at least one electrode is in a state solidified from a melt at least in part of the contact surface (preferably only in part of the contact surface), and the planar joining region of the at least one electrode has an extent in a direction perpendicular to the upper side of the planar joining region of the at least one electrode which varies along the entire contact surface by a maximum of 5% with respect to the total extent of the planar joining region of the at least one electrode in a direction perpendicular to the upper side of the planar joining region of the at least one electrode.

[0062] The composite according to the invention—in contrast to composites produced by ultrasonic welding—exhibits no plastic deformation within the joining area. In other words, the extent of the planar joining area of ​​the at least one electrode perpendicular to its upper side (i.e., its thickness varies) along the entire contact area by a maximum of 5%.

[0063] In the composite, the metallic conductor may be substantially planar along the entire contact surface, which preferably means that a maximum angle between solders dropped onto the top and bottom of the metallic conductor along the entire contact surface is < 1°.

[0064] The contact surface between the two joining regions can be defined by an (imaginary) boundary line, i.e. a line that defines the edge of the contact surface, wherein in a preferred embodiment of the composite the metal of the at least one electrode is in a state solidified from a melt only in a part of the contact surface that is at a certain distance from the boundary line of the contact surface.

[0065] The composite according to the invention can have been produced using a method according to the invention. In this case, the composite according to the invention has at least one feature that necessarily results from carrying out the method according to the invention. The advantages of the method according to the invention thus also result for the composite according to the invention. According to the invention, a battery cell is further provided, containing or consisting of: a) a composite according to the invention as the anode; b) a further composite comprising an electrical conductor and at least one electrode as the cathode, wherein the cathode preferably contains or consists of sulfur; and c) an electrolyte that contacts the electrode of the anode and the electrode of the cathode; d) optionally: a separator arranged between the anode and the cathode.

[0066] The battery cell according to the invention has advantages which result from the composite according to the invention.

[0067] The subject matter of the invention will be explained in more detail with reference to the following figures and examples, without wishing to restrict it to the specific embodiments shown here.

[0068] Figure 1 schematically shows a method according to the invention for producing a composite comprising an electrical conductor and at least one electrode. Figure 1A shows the provision of a plurality of electrodes 1, each consisting of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, wherein the respective electrodes have a flat joining region 2 with a top side and a bottom side. Furthermore, the provision of an electrical conductor 3 is shown, which has a flat joining region 4 with a top side and a bottom side, wherein the flat joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel, and combinations and alloys thereof.In addition, the arrangement of the underside of the planar joining region 2 of one of the electrodes 1 on the top side of the planar joining region 4 of the electrical conductor 3 is shown, wherein a contact surface is created between the underside of the planar joining region 2 of this electrode 1 and the top side of the planar joining region 4 of the electrical conductor 3, which contact surface is defined by a boundary line 5. Furthermore, the irradiation of a laser beam 6 through the joining region 2 of the electrodes 1 onto a part 7 of the contact surface is shown, which part is at a certain distance from the boundary line 5 of the contact surface, so that the metal of the joining region 2 of at least one electrode 1 (near the conductor) and the metal of the joining region 4 of the electrical conductor 3 are heated to a temperature of at least 180°C (preferably at least 220°C) only in that part of the contact surface.In this example, the laser beam is focused on a focal point on the contact surface. Figure 2B shows that the laser beam 6 creates a vapor capillary 8 in the joining region of the electrodes 1, so that an electrode melt is generated locally in this region, which solidifies after the irradiation of the laser beam 6 ends and joins the electrodes 1 together. Furthermore, it is shown how a melt of electrode 1 is created in the part 7 of the contact surface between one of the electrodes 1 (electrode near the arrester) and the electrical arrester 3, onto which the laser beam 6 is focused. The molten electrode 1 can penetrate locally into the surface structure of the joining region 4 of the electrical arrester 3 and, after solidification, form a tight connection between the electrode 1 and the joining region 4 of the electrical arrester 3.

[0069] Figure 2 schematically shows the creation of various patterns in the contact area. The contact area is delimited by the boundary line 5 of the contact area (outer frame of the contact surface between the joining area of ​​the at least one electrode of the electrical conductor). At a specific distance from the boundary line 5, the focal point of the laser beam is moved in a specific pattern in the contact area in order to join the joining area of ​​the at least one electrode to the joining area of ​​the electrical conductor. Figure 2A shows a pattern 9 that has the shape of ellipses, creating elliptical joining seams. Figure 2B shows a pattern 9 that has a zigzag shape, creating a zigzag-shaped joining seam.

[0070] Example 1 - Production of an elliptical joint

[0071] A lithium electrode with a 100 pm thick joining area (so-called "tab") was used as the electrode. The joining areas of a total of 10 such lithium electrodes were arranged one above the other so that the joining area of ​​the electrode had a total thickness of 1000 pm. A nickel-plated copper arrester with a 300 pm thick joining area (so-called "tab") made of nickel-plated copper was used as the electrical conductor.

[0072] The underside of the planar joining area of ​​the electrode (i.e. the stack of the joining areas of a total of 10 lithium electrodes) was arranged on the top side of the planar joining area of ​​the electrical arrester, whereby a contact area was created between the underside of the planar joining area of ​​the electrode and the top side of the planar joining area of ​​the electrical arrester, which contact area was defined by a boundary line.

[0073] A laser beam was then directed through the flat joining area of ​​the electrode onto only a portion of the contact surface that was a certain distance from the boundary line of the contact surface, so that the metal of the joining area of ​​the electrode and the metal of the joining area of ​​the electrical conductor were heated to a temperature of at least 180°C (in particular, at least 220°C) only in that portion of the contact surface. The laser beam was focused onto a focal point on the contact surface. A laser with a laser power of 600 W, a focus diameter of 45 pm, and a focal length of 250 mm was used, and it emitted a laser beam with a wavelength of 1065 nm.

[0074] In this case, the part of the contact surface onto which the laser beam was irradiated had the shape of an ellipse with an ellipse length of 6 mm and an ellipse width of 1 mm. Three irradiations (passes) were performed, each with a beam offset of 0.2 mm (see Figure 2). The focal point was moved along the contact surface at a speed ("scan speed") in the range of 0.5–1.5 m / s. The best result was achieved at a scan speed of 1 m / s.

[0075] In the irradiated area, the joint on the surface of the electrical conductor showed pronounced wetting with lithium. Furthermore, the irradiated area of ​​the joint showed no cohesive cracks and barely measurable contact resistance. Example 2 - Production of a zigzag-shaped joint seam

[0076] A lithium electrode with a 100 pm thick joining area (so-called "tab") was used as the electrode. The joining areas of a total of 10 such lithium electrodes were arranged one above the other so that the joining area of ​​the electrode had a total thickness of 1000 pm.

[0077] A nickel-plated copper arrester was used as the electrical arrester, which had a 300 pm thick joining area (so-called "tab") made of nickel-plated copper.

[0078] The underside of the planar joining area of ​​the electrode (i.e. the stack of the joining areas of a total of 10 lithium electrodes) was arranged on the top side of the planar joining area of ​​the electrical conductor, whereby a contact area was created between the underside of the planar joining area of ​​the electrode and the top side of the planar joining area of ​​the electrical conductor, which contact area was defined by a boundary line.

[0079] A laser beam was then directed through the flat joining area of ​​the electrode onto only a portion of the contact surface, which was a certain distance from the boundary line of the contact surface, so that the metal of the joining area of ​​the electrode and the metal of the joining area of ​​the electrical conductor were heated to a temperature of at least 180°C (in particular, at least 220°C) only in that portion of the contact surface. The laser beam was focused onto a focal point on the contact surface. A laser with a laser power of 600 W, a focus diameter of 45 pm, and a focal length of 250 mm was used. It emitted a laser beam with a wavelength of 1065 nm.

[0080] In this case, the part of the contact surface onto which the laser beam was irradiated had a zigzag shape, with the lines of the zigzag shape at an angle of 30° to each other and the zigzag shape having a total width of 3 mm. The irradiation (passage) was performed l times with a beam offset on the return path (see Figure 3). The focal point was moved along the contact surface at a speed ("scan speed") in the range of 1 - 3 m / s. The best result was achieved at a scan speed of 2 m / s.

[0081] In the irradiated area, the joint on the surface of the electrical conductor showed pronounced wetting with lithium. Furthermore, the irradiated area of ​​the joint showed no cohesive cracks and barely measurable contact resistance.

[0082] 1: Electrode(s);

[0083] 2: Joining area of ​​the electrode(s);

[0084] 3: electrical arrester;

[0085] 4: Joining area of ​​the electrical arrester;

[0086] 5: boundary line of the contact area;

[0087] 6: laser beam;

[0088] 7: Part of the contact surface onto which the laser beam is irradiated;

[0089] 8: Vapor capillary or electrode melt (caused by the

[0090] Laser beam);

[0091] 9: Pattern of movement of the focus point of the laser beam.

Claims

Patent claims 1. A method for producing a composite of an electrical conductor and at least one electrode, comprising the following steps: a) providing at least one electrode consisting of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, wherein the at least one electrode has a planar joining region with a top side and a bottom side; b) providing an electrical conductor having a planar joining region with a top side and a bottom side, wherein the planar joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel, and combinations and alloys thereof;c) arranging the underside of the planar joining region of the at least one electrode on the top side of the planar joining region of the electrical conductor, whereby a contact surface is formed between the underside of the planar joining region of the at least one electrode and the top side of the planar joining region of the electrical conductor; characterized in that the method further comprises irradiating a laser beam through the joining region of the at least one electrode onto at least a portion of the contact surface, so that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor in the portion of the contact surface are heated to a temperature of at least 180°C.

2. The method according to claim 1, characterized in that the planar joining region of the at least one electrode has a thickness in the range of n times from 40 to 140 pm, where n is an integer of at least 30, preferably at least 50, particularly preferably at least 60, very particularly preferably at least 65, in particular at least 70, where the thickness relates to an extension of the joining region perpendicular to its upper side.

3. Method according to one of the preceding claims, characterized in that the planar joining region of the electrical conductor has a thickness in the range from 50 to 400 pm, preferably in the range from 100 to 350 pm, particularly preferably in the range from 200 to 350 nm, wherein the thickness relates to an extension of the joining region perpendicular to its upper side.

4. Method according to one of the preceding claims, characterized in that the contact surface i) is defined by a boundary line, wherein the laser beam is radiated through the joining region of the at least one electrode only onto a part of the contact surface which is at a specific distance from the boundary line of the contact surface; and / or ii) has a length in the range of 0.5 to 20 mm, preferably 1 to 10 mm, in a longitudinal direction along the contact surface; and / or iii) has a width in the range of 0.5 to 6 mm, preferably 1 to 3 mm, in a transverse direction along the contact surface.

5. Method according to one of the preceding claims, characterized in that the laser beam i) is irradiated in such a way that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor are heated to a temperature which at least 190°C, preferably at least 200°C, particularly preferably at least 210°C, in particular at least 220°C; and / or ii) a wavelength in the UV range, VIS range or IR range, preferably a wavelength in the NIR range, particularly preferably a wavelength in the range from 800 to 1400 nm, very particularly preferably a wavelength in the range from 1000 to 1100 nm, in particular a wavelength in the range from 1065 nm; and / or iii) a laser power in a range from 200 to 2000 watts, preferably 300 to 1500 watts, particularly preferably 400 to 1000 W, in particular 500 to 700 watts; and / or iv) has a focal length in the range of 50 to 500 mm, preferably in the range of 100 to 400 mm, particularly preferably in the range of 150 to 350 mm, very particularly preferably in the range of 200 to 300 mm, in particular 250 mm;and / or v) is irradiated onto a part of the contact surface which constitutes >0% to 90%, preferably 2% to 70%, particularly preferably 4% to 50%, very particularly preferably 6% to 30%, in particular 8% to 20%, optionally 10% to 15%, of a total area of ​​the contact surface; 6. Method according to one of the preceding claims, characterized in that the laser beam is focused onto a focal point on the contact surface, wherein the focal point preferably i) has a diameter in the range of 10 to 200 pm, preferably in the range of 20 to 150 pm, particularly preferably in the range of 30 to 100 pm, very particularly preferably in the range of 40 to 50 pm, in particular 45 pm; and / or ii) is moved along the contact surface at a speed in the range of 0.1 to 5 m / sec., preferably in the range of 0.2 to 4 m / sec., particularly preferably in the range of 0.3 to 3.5 m / sec., very particularly preferably in the range from 0.4 to 3 m / sec., optionally in the range from 0.5 to 2 m / sec.; and / or iii) is moved in a pattern along the contact surface, wherein the pattern is selected from the group consisting of circular pattern, elliptical pattern, line-shaped pattern, zigzag pattern and combinations thereof, wherein preferably at least two lines of the zigzag pattern, optionally several lines of the zigzag pattern, are arranged at an angle in the range from 20 to 40°, in particular 30°, to one another; and / or iv) is moved at a distance from a boundary line of the contact surface which is at least 1 mm, preferably at least 2 mm.

7. The method according to any one of the preceding claims, characterized in that i) in step a) at least 29, preferably at least 49, particularly preferably at least 59, very particularly preferably at least 64, in particular at least 69, further electrodes are provided, each consisting of a metal selected from the group consisting of lithium, lithium alloy and combinations thereof, and each having a flat joining region with a top side and a bottom side;and ii) in step e) the planar joining region of each further electrode is arranged on the planar joining region of the at least one electrode, and in step d) the laser beam is irradiated through all planar joining regions of the electrodes onto at least a part of the contact surface, so that the metal of all planar joining regions of the electrodes and the metal of the planar joining region of the electrical conductor in the part of the contact surface are heated to a temperature of at least 180°C; or an upper side of a planar joining region of a single one of the further electrodes on the underside of the planar joining region; of the electrical arrester, wherein a further contact surface is created between the upper side of the planar joining region of the only one of the further electrodes and the underside of the planar joining region of the electrical arrester, wherein the planar joining regions of the other further planar electrodes are arranged at least partially or completely on the planar joining region of the at least one electrode and / or on the planar joining region of the only one of the further electrodes, and in step d) the laser beam is irradiated through all planar joining regions of the electrodes at least onto a part of the contact surface and at least onto a part of the further contact surface, so that the metal of the planar joining regions of all electrodes and the metal of the planar joining region of the electrical arrester in the part of the contact surface and the part of the further contact surface are heated to a temperature of at least 180°C.

8. Plant for producing a composite of an electrical conductor and at least one electrode, comprising: a) at least one electrode consisting of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, wherein the at least one electrode has a planar joining region with a top side and a bottom side; and b) an electrical conductor having a planar joining region with a top side and a bottom side, wherein the planar joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel, and combinations and alloys thereof; wherein the bottom side of the planar joining region of the at least one electrode is arranged on the top side of the planar joining region of the electrical conductor and between the bottom side of the planar joining region of the at least one electrode and the top side of the planar joining region of the electrical conductor, a contact surface exists; characterized in that the system contains a laser which is configured to radiate a laser beam through the planar joining region of the at least one electrode onto at least a part of the contact surface, so that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor in the part of the contact surface are heated to a temperature which is at least 180°C.

9. Plant according to claim 8, characterized in that the planar joining region of the at least one electrode has a thickness in the range of n times from 40 to 140 pm, where n is an integer of at least 30, preferably at least 50, particularly preferably at least 60, very particularly preferably at least 65, in particular at least 70, where the thickness relates to an extension of the joining region perpendicular to its upper side.

10. System according to one of claims 8 or 9, characterized in that the planar joining region of the electrical conductor has a thickness in the range of 50 to 400 pm, preferably in the range of 100 to 350 pm, particularly preferably in the range of 200 to 350 nm, wherein the thickness relates to an extension of the joining region perpendicular to its upper side.

11. System according to one of claims 8 to 10, characterized in that the contact surface i) is defined by a boundary line, wherein the laser of the system is configured to radiate the laser beam through the joining region of the at least one electrode only onto a part of the contact surface which is at a certain distance from the boundary line of the contact surface; and / or ii) in a longitudinal direction along the contact surface has a length in the range of 0.5 to 20 mm, preferably 1 to 10 mm; and / or iii) in a transverse direction along the contact surface has a width in the range of 0.5 to 6, preferably 1 to 3 mm.

12. System according to one of claims 8 to 11, characterized in that the laser of the system is configured, optionally controlled via a control unit of the system, to i) irradiate the laser beam in such a way that the metal of the joining region of the at least one electrode and the metal of the joining region of the electrical conductor are heated to a temperature of at least 190°C, preferably at least 200°C, particularly preferably at least 210°C, in particular at least 220°C; and / or ii) irradiate with a wavelength in the UV range, VIS range or IR range, preferably with a wavelength in the NIR range, particularly preferably with a wavelength in the range of 800 to 1400 nm, very particularly preferably with a wavelength in the range of 1000 to 1100 nm, in particular with a wavelength in the range of 1065 nm;and / or iii) to irradiate with a laser power in a range of 200 to 2000 watts, preferably 300 to 1500 watts, particularly preferably 400 to 1000 W, in particular 500 to 700 watts; and / or iv) to irradiate with a focal length in the range of 50 to 500 mm, preferably in the range of 100 to 400 mm, particularly preferably in the range of 150 to 350 mm, very particularly preferably in the range of 200 to 300 mm, in particular 250 mm; and / or v) to irradiate a part of the contact surface which makes up >0% to 90%, preferably 2% to 70%, particularly preferably 4% to 50%, very particularly preferably 6% to 30%, in particular 8% to 20%, optionally 10% to 15%, of a total area of ​​the contact surface.; 13. System according to one of claims 8 to 12, that the laser of the system is configured, optionally controlled by a control unit of the system, to focus the laser beam on a focus point on the contact surface, preferably the focus point i) to be set so that it has a diameter in the range from 10 to 200 µm, preferably in the range from 20 to 150 µm, particularly preferably in the range from 30 to 100 µm, very particularly preferably in the range from 40 to 50 µm, in particular 45 µm; and / or ii) to be moved along the contact surface at a speed in the range from 0.1 to 5 m / sec., preferably in the range from 0.2 to 4 m / sec., particularly preferably in the range from 0.3 to 3.5 m / sec., very particularly preferably in the range from 0.4 to 3 m / sec., optionally in the range from 0.5 to 2 m / sec., lies; and / or iii) to move in a pattern along the contact surface, wherein the pattern is selected from the group consisting of circular pattern, elliptical pattern, line-shaped pattern and combinations thereof, wherein preferably at least two lines of the line-shaped pattern, optionally several lines of the line-shaped pattern, are arranged at an angle in the range of 20 to 40°, in particular 30°, to one another; and / or iv) to move at a distance from a boundary line of the contact surface which is at least 1 mm, preferably at least 2 mm.

14. System according to one of claims 8 to 13, characterized in that i) the system contains at least 29, preferably at least 49, particularly preferably at least 59, very particularly preferably at least 64, in particular at least 69, further electrodes, each consisting of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, and each having a planar joining region with a top side and a bottom side; and ii) the planar joining region of each further electrode is arranged on the planar joining region of the at least one electrode, and the laser is configured, optionally controlled by a control unit of the system, to radiate the laser beam through all planar joining areas of the electrodes onto at least a portion of the contact surface, so that the metal of all planar joining areas of the electrodes and the metal of the planar joining area of ​​the electrical conductor in the portion of the contact surface is heated to a temperature of at least 180°C; or an upper side of a planar joining area of ​​a single one of the further electrodes is arranged on the underside of the planar joining area of ​​the electrical conductor, wherein a further contact surface exists between the upper side of the planar joining area of ​​the single one of the further electrodes and the underside of the planar joining area of ​​the electrical conductor,wherein the planar joining regions of the other further planar electrodes are arranged at least partially or completely on the planar joining region of the at least one electrode and / or on the planar joining region of the only one of the further electrodes, and the laser is configured, optionally controlled via a control unit of the system, to radiate the laser beam through all planar joining regions of the electrodes at least onto a part of the contact surface and at least onto a part of the further contact surface, so that the metal of the planar joining regions of all electrodes and the metal of the planar joining region of the electrical conductor in the part of the contact surface and in the part of the further contact surface are heated to a temperature of at least 180°C.

15. A composite comprising an electrical conductor and at least one electrode, containing or consisting of: a) at least one electrode made of a metal selected from the group consisting of lithium, lithium alloy, and combinations thereof, wherein the at least one electrode has a planar joining region with a top side and a bottom side; and b) an electrical conductor having a planar joining region with a top side and a bottom side, wherein the planar joining region contains or consists of a metal selected from the group consisting of nickel, copper, stainless steel and combinations and alloys thereof;wherein the joining region of the at least one electrode is arranged on the joining region of the planar electrical conductor and a contact surface exists between the two joining regions, characterized in that the metal of the at least one electrode is in a state solidified from a melt at least in part of the contact surface, and the planar joining region of the at least one electrode has an extent in a direction perpendicular to the upper side of the planar joining region of the at least one electrode which varies along the entire contact surface by a maximum of 5% with respect to the total extent of the planar joining region of the at least one electrode in a direction perpendicular to the upper side of the planar joining region of the at least one electrode.

16. The assembly according to claim 15, characterized in that the metallic conductor is substantially planar along the entire contact surface, which preferably means that a maximum angle between solders dropped onto the top and bottom of the metallic conductor along the entire contact surface is < 1°.

17. Composite according to one of claims 15 or 16, characterized in that the composite was produced by a process according to one of claims 1 to 7.

18. Battery cell containing or consisting of: a) a composite according to one of claims 15 to 17 as anode; b) a further composite comprising an electrical conductor and at least one electrode as a cathode, wherein the cathode preferably contains or consists of sulfur; and c) an electrolyte contacting the electrode of the anode and the electrode of the cathode; d) optionally: a separator arranged between the anode and the cathode.

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