Method and apparatus for impact welding of battery terminals

Abstract

A method includes deforming one or more metal foils of a battery between a punch and a die to form curved metal foils. The one or more curved metal foils are disposed in a foil holding fixture with a battery lead disposed adjacent to the one or more curved metal foils such that a curved portion of the one or more curved metal foils is separated from the battery lead by a distance of 0.1 to 2 millimeters. Impact welding is achieved on the one or more curved metal foils by causing the foils to impact each other or a battery lead at a speed of 300 meters / second to 900 meters / second.

Description

Technical Field

[0001] This document discloses a method and apparatus for impact welding of battery terminals. More specifically, this document discloses a method and apparatus for impact welding metals (including dissimilar metals) to improve weld quality. Background Technology

[0002] Lithium-ion battery packs for vehicles and other high-power applications may include multiple lithium-ion battery cells electrically connected together. Each battery cell includes multiple lithium-ion electrode pairs enclosed within a sealed pouch envelope. Each electrode pair includes a negative electrode, a positive electrode, and a spacer that physically separates and electrically isolates the negative and positive electrodes. To facilitate lithium-ion migration, an electrolyte that conducts lithium ions may be present. During the charge and discharge cycles of the lithium-ion battery cell, the electrolyte allows lithium ions to pass through the spacer between the positive and negative electrodes.

[0003] Depending on their chemical properties, each lithium-ion battery cell has a maximum or charging voltage (the voltage at full charge) due to the electrochemical potential difference between the electrodes. For example, each lithium-ion battery cell may have a charging voltage in the range of 3V to 5V and a nominal open-circuit voltage in the range of 3.5V to 4.5V. Lithium-ion battery cells can be connected in series, parallel, or both, depending on the specified battery pack design.

[0004] Multiple electrode pairs are connected in parallel to store and release electricity electrochemically. Each electrode pair includes an anode and a cathode, with a spacer disposed between them. Each anode has an anode current collector with a negative foil, and each cathode has a cathode current collector with a positive foil. The negative foils of the anodes of the multiple electrode pairs are connected in parallel and electrically connected to a negative terminal lead protruding through the bag, and the positive foils of the cathodes of the multiple electrode pairs are connected in parallel and electrically connected to a positive terminal lead protruding through the bag.

[0005] Within each battery cell, the negative terminal lead is electrically connected to a negative current collector, which contacts and exchanges electrons with the negative electrode of the electrode pair, and the positive terminal lead is electrically connected to a positive current collector, which contacts and exchanges electrons with the positive electrode of the electrode pair. Lithium-ion battery cells are capable of discharging and recharging through numerous cycles.

[0006] The negative foils of the anodes of multiple electrode pairs can be connected in parallel, and can also be electrically connected to the negative terminal lead using laser welding, ultrasonic welding, or other methods. Similarly, the positive foils of the anodes of multiple electrode pairs can be connected in parallel and electrically connected to the positive terminal lead using laser welding.

[0007] Laser welding is a metal joining process in which a laser beam is directed at a stack of metal workpieces to provide a concentrated energy source capable of creating a fusion weld joint between the overlapping constituent metal workpieces. The laser beam is then directed to or near the top surface of the workpiece stack. The heat generated by the absorption of energy supplied by the laser beam triggers the melting of the metal workpieces and establishes a molten weld pool within the workpiece stack. This molten weld pool solidifies to form a weld joint composed of re-cured material from all layers of the metal workpieces.

[0008] Due to numerous factors, including surface conditions, it is known that porosity and / or cracks can form along the laser welding fusion line of a foil. Ultrasonic pre-welding of the foil is used to reinforce it. Subsequently, laser welding of the lead / foil, targeting the pre-welded location, can be used as the final weld. Localized material voids, which can manifest as gaps between layers in a workpiece stack and / or voids in one or more workpieces, can affect the quality of the weld joint and thus the lifespan of the component including the weld joint. When a workpiece stack comprises multiple foils welded to battery leads, the presence of localized material voids can impair the strength of the weld joint and affect the conductivity between one or more foils and the battery leads.

[0009] Therefore, it is desirable to develop new methods for bonding battery foil to leads or for bonding foil together. Summary of the Invention

[0010] One method involves deforming one or more metal foils of a battery between a punch and a die to form a bent metal foil. The one or more bent metal foils are disposed in a foil holding device, with battery leads positioned near the one or more bent metal foils such that the bent portions of the one or more bent metal foils are separated from the battery leads by a distance of 0.1 to 2 mm. Impact welding is achieved by impacting the foils against each other or against the battery leads at a speed of 300 m / s to 900 m / s.

[0011] In one embodiment, one or more bent metal foils are supported on an anvil positioned opposite the foil holding device.

[0012] In another embodiment, the battery leads are placed over one or more bent metal foils in the foil holding device.

[0013] In yet another embodiment, the battery lead has a knurled surface, and the knurled surface faces one or more bent metal foils.

[0014] In yet another embodiment, the opposing non-slip surfaces of the punch and the die are knurled, and one or more bent metal foils are rolled up after deformation.

[0015] In yet another embodiment, impact welding is performed by explosive welding, magnetic pulse welding, evaporation foil actuator welding, laser shock welding, or a combination thereof.

[0016] In yet another embodiment, magnetic pulse welding includes activating one or more coils placed near one or more bent metal foils to enable the one or more bent metal foils to impact each other or impact battery leads. A coil holder including the one or more coils faces a first surface of the one or more bent metal foils, wherein the first surface is opposite to a second surface facing the battery leads.

[0017] In yet another embodiment, magnetic pulse welding includes activating one or more coils placed near one or more bent metal foils to enable the one or more bent metal foils to impact each other or impact battery leads. A coil holder including the one or more coils faces a first surface of the battery leads, wherein the first surface is opposite to a second surface of the battery leads, the second surface of which faces the first surface of the one or more bent metal foils.

[0018] In yet another embodiment, the punch and the die are slidably connected.

[0019] In yet another embodiment, the opposing non-slip surfaces of the punch and the die are provided with a mating convex-concave structure.

[0020] In yet another embodiment, the opposing non-slip mating surfaces of the punch and the die are flat.

[0021] In yet another embodiment, the opposing non-slip mating surfaces of the punch and the die are curved.

[0022] In yet another embodiment, one or more battery foils are heated before or during deformation, wherein heating is performed by resistance heating, infrared heating, laser heating, or a combination thereof.

[0023] In yet another embodiment, the opposing non-slip mating surfaces of the punch and the die are heated by induction heating, resistance heating, or a combination thereof.

[0024] An apparatus for bending one or more battery metal foils includes: a punch; and a die; wherein the punch and the die are slidably connected to each other. The opposing non-slip mating surfaces of the punch and the die are knurled. The opposing non-slip mating surfaces of the punch and the die are heated by induction heating, resistance heating, or a combination thereof. The punch and the die are operable to bend one or more bent metal foils to produce a notch having a height of 0.1 to 2 mm.

[0025] In one embodiment, the opposing non-slip mating surfaces of the punch and the die are curved.

[0026] In another embodiment, the curved surface is hemispherical or semi-cylindrical.

[0027] An apparatus for impact welding one or more bent metal foils includes an anvil and a coil holder containing an electric coil. The anvil is operable to support a battery lead and / or one or more bent metal foils. The electric coil is operable to facilitate impact between the one or more bent metal foils or between the one or more bent metal foils and the battery lead. The one or more bent metal foils are separated from the battery lead by a distance of 0.1 to 2 mm.

[0028] In one embodiment, the impact creates a bond between one or more bent metal foils or between one or more bent foils and battery leads.

[0029] In one embodiment, the anvil contacts one or more curved metal foils on the side opposite to the side that contacts the battery leads.

[0030] The above-described features and advantages, as well as other features and advantages of this disclosure, will become apparent when taken in conjunction with the accompanying drawings and the following detailed description. Attached Figure Description

[0031] Other features, advantages, and details appear by way of example only in the following detailed specification, which refers to the accompanying drawings, wherein:

[0032] Figure 1 This is an exemplary depiction of a battery;

[0033] Figure 2 One aspect of the punch and die used to form the foil of a battery (not shown) before the foil is welded to each other and to the battery cell leads is depicted;

[0034] Figure 3 Another aspect of the punch and die used to form the foil of the battery (not shown) before welding the foils to each other and to the battery cell leads is depicted;

[0035] Figure 4 Another aspect of the punch and die used to form the foil of the battery by using induction heating is depicted;

[0036] Figure 5 Another aspect is depicted: a punch and a die used to form the foil of a battery by means of resistance heating; and

[0037] Figure 6 It is a process flow diagram depicting the process of impact welding bent metal foil. Detailed Implementation

[0038] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or use. It should be understood that throughout the drawings, corresponding reference numerals denote the same or corresponding parts and features.

[0039] This document discloses a forming apparatus comprising a punch and a die, which are used to deform one or more battery foils to create a gap between the battery foils and battery leads, allowing them to be impact-welded together. Deformation is also referred to herein as bending. This gap is used in the impact welding operation to promote an increase in velocity between the battery foils and battery leads when the battery foils are excited. This excitation is sometimes referred to as a “driving force.” The driving force increases the velocity of the foils toward the leads, which in turn contributes to the impact between the foils and leads, thereby creating a weld between the foils themselves and between the foils and leads. The gap provides the foils with the distance required to increase their velocity (during excitation) so that they can impact each other or the battery leads with sufficient force or momentum, thus achieving a bond.

[0040] The foil can be referred to as a flyer (because it moves toward the lead when excited), and the lead is referred to as the target. Impact welding includes different welding processes, such as explosion welding (EXW), magnetic pulse welding (MPW), vaporizing foil actuator welding (VFAW), laser impact welding (LIW), or combinations thereof. In an exemplary embodiment, impact welding is achieved through magnetic pulse welding.

[0041] During bending, the foil and tabs can be interlocked (sometimes called coiling) and joined together by using a punch and die with knurled opposing surfaces. Interlocking primarily refers to the mechanical interlocking that occurs when the mating surfaces are roughened by contact with the knurling deformation force. In this case, the battery foil can be deformed by a punch and die with knurled surfaces. This deformation causes the surface of the battery foil to become rough, and thus they mechanically interlock with each other due to the surface roughness.

[0042] A bond is a contact between two surfaces in which chemical diffusion may occur from one mating surface to the opposite contacting surface. For example, when battery foils are bonded together, components from one foil can diffuse into the adjacent foil. Bonding typically occurs when the temperature rises during the contact between two opposite contacting surfaces. For instance, if the opposite surfaces are knurled at an elevated temperature (at or above the metal's softening point), the opposite surfaces can interlock and bond. If the temperature during knurling does not increase to approximately the metal's softening point, the opposite surfaces will likely interlock but not bond.

[0043] This document also discloses a welding apparatus and a method for performing impact welding to join metal foils of a battery together and / or join metal foils to battery leads. In one embodiment, the battery may be a lithium-ion battery. The method includes bringing a bent battery foil close to the battery leads and exciting the bent foil via a current discharged through a magnetic coil. This excitement causes the battery foil to accelerate through a gap (formed by the bend) and impact the battery leads with a force sufficient to weld the battery foils together or to the battery leads. During this welding process, the battery foils and battery leads can be heated independently, thereby achieving the connection.

[0044] Before describing the apparatus and method for magnetically welding the foil of the battery, a brief introduction to the relevant parts of the battery is given to enhance the understanding of this disclosure.

[0045] Refer to the attached diagram. Figure 1 An embodiment of a prismatic lithium-ion battery cell 10 is schematically illustrated. The prismatic lithium-ion battery cell 10 includes a plurality of electrode pairs 20 arranged in a stacked manner and sealed within a flexible pouch 12 containing electrolytic material 13. A first positive cell lead 29 and a second negative cell lead 24 protrude from the flexible pouch 12. Each electrode pair 20 includes an anode 21 disposed on an anode (or negative) current collector 22 and a cathode 26 disposed on a cathode (or positive) current collector 27, and is separated by a spacer 25. The cathode current collector 27 is made of aluminum or an aluminum alloy and includes a positive electrode foil (or cathode foil) 28. The anode current collector 22 is made of copper, a copper alloy, or another material and includes a negative electrode foil (or anode foil) 23.

[0046] Negative current collector 22 and positive current collector 27 are thin metal plates that contact their respective negative electrodes 21 and positive electrodes 26 over a considerable interfacial surface area. The purpose of these metal current collectors 22, 27 is to exchange free electrons with their respective negative electrodes 21 and positive electrodes 26 during the discharge and charging of the electrode pair 20. To facilitate the overall distribution and flow of electrons, each negative current collector 22 includes a negative electrode foil 23, and each positive current collector 27 includes a positive electrode foil 28.

[0047] Multiple negative electrode foils 23 are positioned opposite the electrode pair 20 and overlap each other in alignment, and multiple positive electrode foils 28 are also positioned opposite the electrode pair 20 and overlap each other in alignment. The aligned set of negative electrode foils 23 and positive electrode foils 28 are separated from each other on different sides of the electrode pair 20 (as shown) or on the same side of the electrode pair 20 (not shown). Multiple positive electrode foils 28 of the cathode current collector 27 are arranged in the first stack 14 and are electrically coupled and mechanically connected to the positive cell lead 29 in a manner described herein. Multiple negative electrode foils 23 of the anode current collector 22 are arranged in the second stack 16 and are electrically coupled and mechanically bonded to the second negative cell lead 24.

[0048] Each electrode pair 20 includes a positive electrode (or cathode) 26, a negative electrode (or anode) 21, and a spacer 25 disposed between the positive electrode 26 and the negative electrode 21 to physically separate and electrically insulate the positive electrode 26 and the negative electrode 21 from each other. An electrolytic material 13 that conducts lithium ions is contained within the spacer 25 and exposed to each of the positive electrode 26 and the negative electrode 21 to allow lithium ions to move between the positive electrode 26 and the negative electrode 21.

[0049] The apparatus and method disclosed herein are used to connect multiple positive electrode foils 28 together to form a first stack 14 and to connect multiple negative electrode foils 23 together to form a second stack 16. The use of impact welding has several significant advantages compared to other known methods—notably, it can be used to connect dissimilar metals, and metals with oxide coatings and contaminants, without any adverse effects on the battery.

[0050] As described above, impact welding uses a driving force and an appropriate gap (between the flyer and the target) to produce a solid-state weld at approximately room temperature. This weld is completed in a few microseconds and can be stronger than the bonded base metal.

[0051] In magnetic pulse welding, a conductive workpiece is placed inside or near an electric coil, which accelerates it a short distance, causing it to impact a second workpiece at extremely high speed. A large amount of energy in the form of an electric current is discharged through the coil in a very short time. Some systems can discharge up to 2 million amperes in less than or equal to 100 microseconds. The acceleration is a result of the repulsive magnetic field between the workpiece and the coil, generated by eddy currents in the workpiece. The reaction force between the opposing magnetic fields forces the workpieces toward each other at high speed, initiating the weld. The impact velocity is typically 300-900 m / s. Magnetic shock welding is the preferred form of impact welding.

[0052] Solid-state welding occurs when two metals are forced together by the strength at which their atoms begin to share electrons, effectively joining the two metals together. The actual process lasts no more than 100 microseconds. Because it does not involve heating or melting, this technique can be used to weld dissimilar metals. Impact welding triggers this phenomenon by accelerating a metal to a viscoplastic phase and impacting another workpiece to achieve a bond. No protective atmosphere, filler material, or other auxiliary materials are used in this bonding process. Magnetic pulse welding is a “cold” or at most “warm” welding process; the temperature is significantly lower than the melting temperature of the metal. Therefore, no fusion zone is created. The welded part can be the strongest part of the component. Impact welding is highly repeatable, reproducible, and reliable, making it ideal for high-volume production. Many welding combinations using dissimilar metals are possible. It is a welded joint without a heat-affected zone. The bond between different metals is of high quality, very aesthetically pleasing, and produces a cleaner interface. The joint retains mechanical strength (a typical joint can be stronger than the base metal). All these advantages translate into significantly lower costs and much higher quality and productivity.

[0053] Figure 2 One aspect of a forming apparatus 200 is depicted for forming (also bending) the foil 302 of a battery (not shown) prior to welding the foils together and to the battery cell leads 304. The battery may have one or more metal foils. Although the foil is sometimes referred to as multiple foils herein, it should be understood that a battery may have a single foil or multiple foils. When the battery has a single foil, it is welded to the battery leads. Alternatively, when the battery comprises multiple foils, the foils may be welded together and to the battery leads. These foils are referred to herein as metal foils.

[0054] The battery cell lead 304 (also referred to as battery lead 304) is typically made of copper or aluminum. In one embodiment, the surface of the battery lead 304 is knurled (or has a surface texture / protrusion) to further enhance the soldering quality between the lead and the foil disposed thereon. The knurling of the battery lead creates surface roughness that increases the gap between the lead 304 and the nearest foil (among a plurality of bent foils 302), which allows the foil to accelerate when subjected to an opposing magnetic field. This gap provides space for the bent foils 302 to accelerate toward the lead 304 and solder to the lead 304 upon impact. This allows for a good soldering between the bent foils 302 and the battery lead 304.

[0055] The forming apparatus 200 includes a punch 204 and a die 202 that are slidably connected to each other. In other words, when the metal foil is located between the punch and the die 202, the punch 204 can engage with the die 202 to bend the metal foil 302 of the battery. The first surfaces 203 of the punch 204 that are in contact with the opposing first surfaces 205 of the die 202 are knurled. When the foil is pressed between the punch 204 and the die 202, the knurled first surfaces 203 and the opposing knurled first surfaces 205 promote adhesion and create interlocking between the foils. Knurling improves the interlocking and bonding between the foils.

[0056] Each metal foil 302 typically has an individual thickness of 6 to 16 micrometers. Stacks typically comprise 6 to 240 metal foils. After the metal foils 302 are placed between the punch 204 and the die 202, the punch 204 moves toward the die 202. Compressive force is applied to the metal foils 302 via the punch 204. The metal foils 302 deform (e.g., bend) to take a shape determined by the shapes of the opposing surfaces of the punch 205 and the die 203. During bending, the knurled surfaces 205 and 203 of the punch and die respectively promote interlocking and bonding of the metal foils, resulting in increased surface area contact between the metal foils 302 of the battery. After the metal foils are bent, the punch moves away from the die, and a new set of metal foils can be placed in the space between the punch and the die. This process is repeated to produce another set of bent metal foils 303.

[0057] After the metal foil 303 is bent, it undergoes impact welding in a welding apparatus 400 including an anvil 208 and a coil holder 206. The anvil 208 provides physical support for the battery lead 304 during the impact welding process. The coil holder 206 is made of an electrically insulating material and includes one or more magnetic coils 210 that bring the bent metal foil 303 into contact with the battery lead 304 at high speed.

[0058] In one method of operating the welding apparatus 400, a battery lead 304 is disposed on a bent foil 303. The battery lead 304 has a thickness of 0.1 to 0.6 mm. An anvil 208 is disposed on the battery lead 304. A coil holder 206 containing a magnetic coil 210 is then brought close to the bent metal foil 303 and the battery lead 304. The bent metal foil 303 is located on the side of the battery lead 304 opposite to the anvil 208.

[0059] In other words, reference Figure 2The coil holder 206 faces the first surface 302a of the bent metal foil 303. The second surface 302b of the bent metal foil (opposite to the first surface of the bent metal foil 303) faces the first surface 304a of the battery lead 304. The second surface 304b of the battery lead 304 (opposite to the first surface 304a of the battery lead 304) faces the anvil 208. In another embodiment ( Figure 2 In (not shown), the battery lead 304 and the bent metal foil 303 can be interchanged, such that the first surface 304a of the battery lead 304 faces the coil holder 206, while the opposite second surface 304b faces the first surface 302a of the battery foil. The second surface 302b of the battery foil faces the anvil 208.

[0060] The coil 210 is energized (allowing current to flow through the coil), which generates a magnetic force that causes the foil 303 to contact the lead 304 at high speed. The electrical insulating material can be a polymer or ceramic. The distance between the bent metal foil 303 and the lead 304 is... Figure 2 This is shown as d1. d1 is expected to be 0.1 to 2.0 mm. In other words, the punch and die create a notch (d1) of 0.1 to 2 mm in the metal foil. This distance allows the bent metal foil 303 to impact the lead 304 with sufficient speed, force, and momentum (when excited) to achieve a successful connection with the lead 304.

[0061] In one embodiment, the welding apparatus 400 may include clamps (not shown) to press down on the bent foils and bring them into contact with the battery leads, or alternatively, as close as possible to the battery leads 304. In an embodiment, a coil holder (comprising multiple coils) (not shown) may be moved into position such that each of the multiple coils is directly above a bent portion of the battery foil (when the battery foil contains multiple bent portions) (not shown). Current is then passed through the multiple coils. Opposing magnetic fields cause the foils to accelerate toward each other and impact each other to bond together. In one embodiment, the foils accelerate toward the leads to bond with the leads, thereby forming a weld 306.

[0062] It should be noted that, although Figure 2 The coil holder 206 shown is depicted as a single coil 210, but the coil holder may comprise multiple coils (not shown), each located near a bent portion of the battery foil. The multiple coils may all be energized simultaneously or sequentially to facilitate contact between the foil and the leads, thereby enabling soldering. The coils may be connected to a power source (not shown).

[0063] In one embodiment, during the welding process in device 400, the bent foil and battery leads can be independently heated before or during the impact welding process. This independent heating can be achieved through infrared heating, convection heating, laser heating, or a combination thereof. This heating can promote the bonding of the bent foil to each other or to the battery leads.

[0064] Figure 3 Another aspect of the forming apparatus 200 is depicted, which includes a punch 204 and a die 202 for bending the foil 302 of the battery (not shown) before welding the foil 302 to each other and to the battery cell leads 304 (in the welding apparatus 400). The punch 204 and the die 202 are again slidably connected to each other. In this case, the opposing surfaces 205 and 203 of the punch 204 and the die 202 are hemispherical or semi-cylindrical, respectively, and are arranged in a concave-convex fit configuration. For example, surface 205 may protrude into surface 203 (or vice versa), and multiple metal foils can be bent to interlock and connect them. When surface 205 is provided with a convex configuration, it protrudes into surface 203, which is provided with a concave configuration. Alternatively, when surface 203 is provided with a concave configuration, it protrudes into surface 205, which is provided with a convex configuration.

[0065] The opposing surfaces 205 and 203 (non-sliply connected to each other) fit together and may be knurled. For example... Figure 2 As discussed in the paper, when the metal foil is located between the punch and the die 202, the punch 204 can engage with the die 202 to bend the metal foil 302 of the battery.

[0066] When the foil is pressed between the punch 204 and the die 202, the knurled first surface 205 and the knurled opposing first surface 203 promote interlocking and bonding between the foils.

[0067] Figure 3 A welding apparatus 400 is also depicted, comprising an anvil 208 supporting battery leads 304 and a plurality of battery foils 302 during impact welding. During the generation of a magnetic pulse, a coil holder 206 containing an electric coil 210 may be positioned below or above the bent foil, the magnetic pulse causing welding in the foils 302 and welding of the battery foils 302 to the leads 304. The functions of the anvil and coil holder have been described in detail above and will not be described in detail again.

[0068] Figure 3 Two embodiments of how the anvil 208 and coil holder 206 can be used are depicted. In one embodiment (in... Figure 3(See lower left), the coil holder 206 is positioned on one side of the bent foil 302, while the battery lead 304 is located on the opposite side of the bent foil 302. An anvil supporting the battery lead 304 is located on the side of the battery lead opposite to the side facing the bent foil 302. In another embodiment (see...) Figure 3 (Lower right side), coil holder 206 is located above battery lead 304, while bent battery foil 302 is located below battery lead 304. An anvil 208 with a surface 209 for accommodating bent foil 302 is used to support the foil during the impact welding process.

[0069] in short, Figure 3 The anvil and coil holder can be reversed around the bent foil and leads. When the anvil is near the battery leads, the coil holder is near the bent foil, and vice versa, while the battery leads and bent foil are always directly adjacent to each other.

[0070] In both embodiments (in) Figure 3 (Depicted on the lower left and lower right sides), energizing the coil in the coil holder promotes the movement of the bent foil toward the battery leads, thereby causing soldering.

[0071] Figure 4 This is another exemplary depiction of a forming apparatus 200, wherein an induction coil 210 and a die 202 (slidably connected to each other) are respectively provided with induction coils 210 and 212 to heat the punch and the die. Induction coils 210 and 212 are located near opposing mating surfaces 205 and 203, respectively, and heat the metal foil by induction heating. Induction heating is a process of heating a material (e.g., a metal) through electromagnetic induction. An induction heater consists of an electromagnet (not shown) and an electronic oscillator (not shown) through which high-frequency alternating current (AC) is passed. A rapidly alternating magnetic field penetrates the object, generating a current called eddy current within the conductor. The eddy current flows through the resistance of the material and heats it by Joule heating.

[0072] Induction heating is used to heat the opposing mating surfaces 205 and 203 to soften the metal foil 302 disposed between the punch and the die, thereby producing a bent metal foil 303. The punch and the die apply compressive force to achieve bonding and interlocking of the metal foil during the induction heating process.

[0073] The opposing surfaces 205 and 203 of the punch 204 and the die 202 can be flat (e.g., Figure 2 (as shown), or it can be hemispherical or semi-cylindrical (as shown). Figure 4 As shown above), and in accordance with the above text Figure 3 The concave-convex fit construction arrangement is described in detail. The opposing mating surfaces 205 and 203 may be knurled.

[0074] After the bent metal foils 303 are formed, they can be placed in the welding apparatus 400 adjacent to the battery leads 304 and subjected to magnetic force (via a coil holder 206 containing a coil 210) to facilitate bonding of the metal foils to each other and connection to the leads. This process has already been completed. Figure 2 The details are described in detail below, and will not be repeated for the sake of brevity.

[0075] As previously Figure 3 As seen in the text, Figure 4 The anvil and coil holder can be reversed around the bent foil and leads. When the anvil is near the battery leads, the coil holder is near the bent foil, and vice versa.

[0076] Figure 5 Another exemplary method for forming battery metal foil 302 using forming apparatus 200 includes a punch 204 and a die 202, both of which are heated by resistance heating. In this case, both the punch 204 and the die 202 are provided with electrical coils (214 and 218, respectively) and cooling systems (216 and 220, respectively). The electrical coils 214 and 218 heat the surfaces of the punch and the die by conduction (heat comes from the resistance heating of the coils 214 and 218). The cooling system can use cooling water to control the heat generated on the surfaces of the punch and the die and maintain the punch and the die at a desired temperature.

[0077] The heat generated by the coils 214 and 218 is used to heat the opposing mating surfaces 205 and 203 to soften the metal foil 302 disposed between the punch and the die, thereby producing a bent metal foil 303. The punch and the die apply compressive force to the metal foil to achieve bonding and interlocking of the metal foil during induction heating.

[0078] The opposing surfaces 205 and 203 of the punch 204 and the die 202 can be flat (e.g., Figure 2 (as shown), or it can be hemispherical or semi-cylindrical (as shown). Figure 5 As shown above), and in accordance with the above text Figure 3 The concave-convex mating structure arrangement is described in detail. The opposing mating surfaces 205 and 203 can be knurled. After the metal foils 303 are bent, they can be positioned adjacent to the battery leads 304 in the welding apparatus 400 and subjected to magnetic force via the coil 210 (included in the coil holder 206) to facilitate the connection of the metal foils to each other and to the leads. This process has already been described... Figure 2 The details are described in detail below, and for the sake of brevity, they will not be repeated. For example... Figure 3 and Figure 4As shown, the anvil 208 and coil holder 206 can be reversed in position around the curved metal foil and battery leads. When the anvil is near the battery leads, the coil holder is near the curved foil, and vice versa.

[0079] Figure 6 A process 500 for impact welding battery foil to battery leads is described. In step 502, the battery foil is placed between a punch and a die and deformed to form a bent metal foil. The battery foil may optionally be heated before or during the foil deformation process (step 503) (step 501). The bent metal foil is then placed near the battery leads (step 504). The battery leads are then placed together with adjacent battery foils between a coil holder and an anvil (step 506). A coil in the coil holder is activated (step 508) to facilitate impact between the foils themselves or between the foil and the leads, thereby achieving welding.

[0080] The process of using magnetic welding to bond foils together or to attach foils to leads is advantageous because dissimilar metals can be joined together. Contaminants do not damage or weaken the bond. This method can be a viable alternative to the two-step ultrasonic / ultrasonic or ultrasonic / laser welding process used in batteries—which sometimes leads to battery failure. This method also enables dissimilar metals to be bonded to reduce defects (intermetallic compounds, porosity, and thermal cracking) and is more resistant to surface oxides / contamination.

[0081] While the foregoing disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and elements can be substituted with equivalents without departing from its scope. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this disclosure without departing from the basic scope of this disclosure. Therefore, it is intended that this disclosure be limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. An impact welding method for multiple bent metal foils, comprising: Multiple metal foils of the battery are stacked on top of each other between a punch and a die, wherein each metal foil has an individual thickness of 6 to 16 micrometers and 6 to 240 metal foils are stacked on top of each other; The punch is moved toward the die, and a compressive force is applied to the plurality of metal foils via the punch to deform the plurality of metal foils to form a plurality of bent metal foils, wherein the punch and the die have knurled surfaces to promote interlocking and bonding of the plurality of metal foils and result in increased surface area contact between the plurality of metal foils; The plurality of bent metal foils are arranged in a foil holding and fixing device; The battery lead is positioned near the plurality of bent metal foils such that the bent portions of the plurality of bent metal foils are separated from the battery lead by a distance of 0.1 to 2 millimeters. as well as Impact welding is achieved by causing the multiple bent metal foils to impact each other or impact the battery leads at a speed of 300 m / s to 900 m / s. In this process, the bent foil and battery leads are heated independently during the impact welding process, and the punch and die are equipped with a cooling system to control the heat generated on the surface of the punch and die and to keep the punch and die at the desired temperature.

2. The impact welding method according to claim 1 further includes supporting the plurality of bent metal foils on an anvil in the foil holding and fixing device.

3. The impact welding method according to claim 1 further includes placing the battery lead above the plurality of bent metal foils in the foil holding and fixing device.

4. The impact welding method according to claim 1, wherein the opposing non-slip surfaces of the punch and the die are knurled, and wherein the bent metal foil is rolled up after the deformation.

5. The impact welding method according to claim 1, wherein the impact welding is performed by explosive welding, magnetic pulse welding, evaporation foil actuator welding, laser shock welding, or a combination thereof.

6. The impact welding method according to claim 5, wherein, The magnetic pulse welding includes activating one or more coils placed close to the plurality of bent metal foils to enable the plurality of bent metal foils to impact each other or impact the battery leads; including a coil holder of the one or more coils facing a first surface of the plurality of bent metal foils; wherein the first surface is opposite to a second surface facing the battery leads.

7. The impact welding method according to claim 5, wherein, The magnetic pulse welding includes activating one or more coils placed close to the plurality of bent metal foils to enable the plurality of bent metal foils to impact each other or impact the battery leads; including a coil holder of the one or more coils facing a first surface of the battery leads; wherein the first surface is opposite to a second surface of the battery leads, the second surface facing the first surface of the plurality of bent metal foils.

8. An apparatus for bending battery metal foil, the apparatus comprising, according to any one of claims 1-7, performing an impact welding method for bending multiple metal foils, comprising: Punch head; as well as Mold; The punch and the die are slidably connected to each other; The opposing non-slip mating surfaces of the punch and the die are knurled; wherein the opposing non-slip mating surfaces of the punch and the die are heated by induction heating, resistance heating or a combination thereof, so that the bent foil and battery leads are independently heated during the impact welding process; wherein the punch and the die are operable to bend multiple foils to produce notches with a height of 0.1 to 2 mm. Each metal foil has an individual thickness of 6 to 16 micrometers, and 6 to 240 metal foils are stacked on top of each other; Furthermore, the punch and die are equipped with a cooling system to control the heat generated on the surface of the punch and die and to keep the punch and die at the desired temperature.

9. An apparatus for impact welding of multiple bent metal foils, comprising: Anvil; The anvil is operable to support battery leads and / or a plurality of bent metal foils, the plurality of bent metal foils being formed by the device as described in claim 8; as well as A coil holder that houses an electric coil; wherein the electric coil is operable to facilitate impacts between the plurality of bent metal foils or between the plurality of bent metal foils and the battery leads; wherein the plurality of bent metal foils are separated from the battery leads by a distance of 0.1 to 2 millimeters; wherein the device causes the plurality of bent metal foils to impact each other or impact the battery leads at a speed of 300 m / s to 900 m / s.

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