HYBRID FILM WELDING JOINT AND WELDING PROCESS

Abstract

Battery cell, method for welding electrode foils in a battery, and method for forming a battery cell. The battery comprises a foil stack. The foil stack has a plurality of foil tabs, each extending from a current collector and at least one internal connecting lead. The battery further comprises a weld joint formed between the plurality of foil tabs and the at least one connecting lead in the foil stack. A portion of the weld joint has a weld lens extending across the plurality of foils into the internal connecting lead, and the remainder of the weld joint has a diffusion bond zone extending around at least one portion of the weld lens.

Description

introduction

[0001] The technology of electric and hybrid electric vehicles is enabled by the development and use of rechargeable secondary batteries that supply energy to the vehicle's powertrain. Secondary batteries, including lithium-ion batteries, often contain an array of battery cells. Each battery cell generally has a cathode, an anode, a separator, and an electrolyte. The cathode provides the source of lithium ions and determines the battery's capacity and average voltage. The anode stores and releases lithium ions received from the cathode when energy is needed. The separator prevents the cathode and anode from touching and short-circuiting the battery, and the electrolyte provides a medium between the cathode and anode through which the lithium ions move.The energy density or areal capacity of the secondary battery can be increased by adding more cathode and anode active material and increasing the density of the cathode and anode.

[0002] In secondary batteries with prismatic battery cells, the cathode electrode, anode electrode, and separator can be wound or stacked into a flattened, jelly-roll configuration, with a ribbon-like separator nested between layers of the cathode and anode electrodes and folded in a manner resembling a z-pattern. In prismatic battery cells, the cathode and anode electrodes have foil tabs extending from the jelly roll or stack. The foils for the cathode electrodes are connected to the internal cathode leads, and foils for the anode electrodes are connected to the anode leads. Typically, the foils are joined to the leads by an ultrasonic or laser welding process. In these processes, gaps present between the foils create pores during welding.Furthermore, the use of materials that can exhibit relatively high degrees of thermal expansion, such as aluminum, but are fixed in place during the welding process, can cause bulging when the material is heated, further developing and enlarging air inclusions and pores. Additionally, separation of the foils from the weld joint can occur during welding.

[0003] Nevertheless, the existing welding processes achieve their intended purpose. However, there remains a need for new and improved welding processes that offer enhanced weld joint stability. Description

[0004] According to various aspects, the present description relates to a battery cell. The battery comprises a foil stack. The foil stack has a plurality of foil tabs, each extending from a current collector and at least one internal connecting lead. The battery also has a weld joint formed between the plurality of foil tabs and the at least one connecting lead in the foil stack. One section of the weld joint has a weld lens extending across the plurality of foils into the internal connecting lead, and the remainder of the weld joint has a diffusion bond zone extending around at least one section of the weld lens.

[0005] In embodiments of the foregoing, the weld lens has a depth in the range of 250 micrometers to 2,200 micrometers relative to an incidence surface, and the diffusion bonding zone has a depth in the range of 300 micrometers to 2,600 micrometers relative to the incidence surface.

[0006] In any one of the foregoing embodiments, at least one connecting line comprises a first connecting line and a second connecting line. The first connecting line provides a first outer surface of the film stack, and the second connecting line provides a second outer surface of the film stack. Alternatively, the at least one connecting line is arranged between two of the plurality of films and one of the plurality of films.

[0007] In any one of the foregoing embodiments, the plurality of films ranges from two to 300 films.

[0008] In any of the foregoing embodiments, the internal connecting leads have a thickness in the range of 0.5 millimeters to 5 millimeters. In further embodiments, the current collector is a cathode current collector, and each cathode current collector has a thickness in the range of 5 micrometers to 50 micrometers. In further embodiments, the cathode current collector is made of aluminum, and the internal connecting lead is made of aluminum. Alternatively, the current collector is an anode current collector, and each anode current collector has a thickness in the range of 4 micrometers to 50 micrometers. In further embodiments, the anode current collector is made of copper, and the internal connecting lead is made of copper.

[0009] In any one of the foregoing embodiments, the weld joint has at least one of an edge joint, an overlap joint and an overlap joint.

[0010] According to various additional aspects, the present description relates to a method for welding electrode foils in a battery. The method comprises clamping a foil stack together with at least two clamps and applying pressure to the foil stack with the clamps. The foil stack has a plurality of foil tabs, each extending from a current collector and at least one internal connecting lead. A first of the two clamps is positioned on a first outer surface of the foil stack, and a second of the at least two clamps is positioned on a second outer surface of the foil stack. The method further comprises emitting a light beam from a laser onto the second outer surface of the foil stack. The light beam has a total power of emitted light and emits light in a core and ring pattern.The core power ranges from 30% to 70% of the total emitted light power, and the ring power ranges from 30% to 70% of the total emitted light power. The process further involves the formation of a weld. One section of the weld has a weld lens formed at least partially by the core of the laser beam, and the remainder of the weld has a diffusion bond zone formed at least partially by the ring of the laser beam.

[0011] In embodiments of the foregoing, the method further comprises the formation of the weld lens to a depth relative to an incidence surface on the second outer surface of the film stack in the range of 250 micrometers to 2,200 micrometers. In further embodiments, the method also comprises the formation of the diffusion bonding zone to a depth relative to an incidence surface on the second outer surface of the film stack in the range of 300 micrometers to 2,200 micrometers.

[0012] In one of the foregoing embodiments, the at least two clamps comprise a third clamp which is placed adjacent to the second side of the outer surface of the film stack, and the method further comprises placing the second clamp on one side of a location on the circumference of a point at which the light beam is incident on the film stack, and placing the third clamp on the other side of the location on the circumference of the light beam incident on the film stack.

[0013] In one of the above embodiments, the method further comprises emitting the light beam at the core with a power in the range of 1,000 W to 2,000 W and emitting the light beam at the ring in the range of 500 W to 1,500 W.

[0014] In one of the above embodiments, the ratio of the core diameter to the ring diameter in the core and ring pattern is in the range of 1:1.5 to 1:4.

[0015] In one of the aforementioned embodiments, the method further comprises the light beam over the second outer surface at a welding speed in the range of 5 millimeters per second to 150 millimeters per second. In other embodiments, the welding speed is in the range of 40 millimeters per second to 90 millimeters per second.

[0016] In one of the foregoing embodiments, the method further comprises shaping the light beam, wherein the ring is formed into a semicircle.

[0017] In one of the foregoing embodiments, the method further features the oscillation of the light beam.

[0018] In one of the foregoing embodiments, the method further comprises arranging a first of the at least one internal connecting lines on the first outer surface of the film stack.

[0019] In one of the foregoing embodiments, the method further comprises arranging a second of the at least one internal connecting lines on the second outer side of the film stack.

[0020] In one of the foregoing embodiments, the method further comprises the arrangement of the at least one internal connecting lines between two of the plurality of films in the film stack.

[0021] In one of the foregoing embodiments, the current collector is a cathode current collector, with 1 to 300 cathode electrodes present and a thickness ranging from 5 to 50 micrometers. Alternatively, in one of the foregoing embodiments, the current collector is an anode current collector, with 1 to 300 anode current collectors present and a thickness ranging from 4 to 50 micrometers.

[0022] In one of the foregoing embodiments, the plurality of foils is aluminum and has a thickness in the range of 5 micrometers to 50 micrometers, and the at least one internal connecting line is aluminum and has a thickness in the range of 0.5 millimeters to 5 millimeters.

[0023] According to various additional aspects, the present description relates to a method for forming a battery cell for a vehicle. The method comprises arranging at least one cathode electrode, including a cathode current collector, at least one anode electrode, and at least one separator in at least one stacked configuration and one jelly roll configuration. The method further comprises clamping a film stack with at least two clamps and applying pressure to the film stack with the clamps. The film stack has a film extending from the cathode current collector and at least one internal connecting line. A first of the two clamps is positioned on a first outer surface of the film stack, and a second of the at least two clamps is positioned on a second outer surface of the film stack.The method further comprises emitting a laser beam onto the second outer surface of the foil stack. The laser beam has a total emitted light power of [missing value] and emits light in a core and ring pattern. The core power is in the range of 30 percent to 70 percent of the total emitted light power, and the ring power is also in the range of 30 percent to 70 percent of the total emitted light power. The method also comprises forming a weld. One section of the weld has a weld lens formed at least partially by the core of the laser beam, and the remainder of the weld has a diffusion bond zone formed at least partially by the ring of the laser beam.The method also includes placing the arranged at least one cathode electrode including a cathode current collector, at least one anode electrode and at least one separator into a prismatic housing, connecting the internal connecting leads to external connecting leads, sealing the battery housing and adding electrolyte to the battery housing.

[0024] In embodiments of the foregoing, the method further comprises forming the welding lens to a depth relative to an incidence surface on the second outer side of the film stack in the range of 250 micrometers to 2,200 micrometers and forming the diffusion bonding zone to a depth relative to an incidence surface on the second outer side of the film stack in the range of 300 micrometers to 2,200 micrometers.

[0025] In one of the foregoing embodiments, the method comprises emitting the light beam at the core with a power in the range of 1,000 W to 2,000 W and emitting the light beam at the ring in the range of 500 W to 1,500 W, wherein the ratio of the diameter of the core to the diameter of the ring in the core and ring pattern is in the range of 1:1.5 to 1:4 and the welding speed is in the range of 5 millimeters per second to 150 millimeters per second.

[0026] In one of the foregoing embodiments, the plurality of foils is aluminum and has a thickness in the range of 5 micrometers to 50 micrometers, and the at least one internal connecting line is aluminum and has a thickness in the range of 0.5 millimeters to 5 millimeters. Brief description of the drawings

[0027] The drawings described herein serve only for illustration and are not intended to limit the scope of the present description in any way. Fig. Figure 1 illustrates a vehicle and a powertrain with a secondary battery according to embodiments of the present description. Fig. 2A illustrates a battery according to embodiments of the present description. Fig. Figure 2B illustrates an exploded view of a battery cell according to embodiments of the present description. Fig. Figure 3 illustrates cathode electrodes, anode electrodes and a separator stacked in a z-stack, wherein the separator is nested between the cathode electrodes and the anode electrodes according to embodiments of the present description. Fig. Figure 4 illustrates a cathode electrode, an anode electrode and two separators wound into a flattened jelly roll configuration, according to embodiments of the present description. Fig. Figure 5 illustrates a cross-section of a battery cell according to embodiments of the present description. Fig. Figure 6 illustrates a method for welding a stack of foil according to embodiments of the present description. Fig. Figure 7 illustrates an end weld according to embodiments of the present description. Fig. Figure 8A illustrates an overlap weld, wherein the foil stack has two internal connecting lines according to embodiments of the present description. Fig. Figure 8B illustrates an overlap weld wherein the foil stack has an internal connecting line according to embodiments of the present description. Fig. Figure 9A illustrates an overlap weld wherein the foil stack has two internal connecting lines according to embodiments of the present description. Fig. Figure 9B illustrates an overlap weld wherein the foil stack has an internal connecting line according to embodiments of the present description. Fig. Figure 10 illustrates the core and ring pattern of a light beam according to embodiments of the present description. Fig. Figure 11A illustrates a core and ring pattern of a light beam according to embodiments of the present description. Fig. Figure 11B illustrates a diagram of power versus distance from the center of a light beam according to embodiments of the present description. Fig. Figure 12A illustrates an oscillation pattern of a light beam according to embodiments of the present description. Fig. Figure 12B illustrates a diagram of power versus distance from the center of a light beam according to embodiments of the present description. Fig. Figure 13 illustrates a method for forming a battery cell according to embodiments of the present description. Fig. Figure 14 illustrates a diagram of the tensile strength of a comparative ultrasonic and laser overlap joint compared to the tensile strength of a laser weld formed according to embodiments of the present description. Fig. Figure 15 illustrates the weld depth of the weld lens and the depth of the diffusion bonding zone, illustrated on the primary y-axis on the left, and the tensile strength, illustrated on the secondary y-axis on the right, as a function of the percentage of core laser power, illustrated on the horizontal x-axis, according to embodiments of the present description. Fig. Figure 16A illustrates an image of a joint failure after tensile testing, wherein the welded joint was produced according to embodiments of the present description. Fig. Figure 16B illustrates a close-up of the dashed line box of Fig. 16A. Fig. Figure 17 illustrates a close-up of the welded foils after a joint failure during tensile testing, wherein the weld joint was produced according to embodiments of the present description. Fig. Figure 18 illustrates the resistance over a weld joint produced in accordance with changes to the present description before and after tensile testing. Detailed description

[0028] The following description is merely exemplary and is not intended to limit the present description, application, or uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, description, or subsequent detailed description. It is understood that in the drawings, identical reference numerals denote identical or corresponding parts and features.

[0029] Several examples of the description, illustrated in the accompanying drawings, are now referred to in detail. Where possible, the same or similar reference symbols are used in the drawings and the description to refer to identical or similar parts or steps. The drawings are simplified and not to scale.

[0030] The use of terms like "first," "second," "third," "fourth," etc., in the description and claims to designate elements is arbitrary and intended to facilitate understanding of the description. These references are not necessarily consistent between embodiments or between the description and the claims. In this sense, these references are not intended to restrict the elements in any way. The elements are distinguishable by their arrangement, description, connections, and function.

[0031] The present description generally refers to a hybrid foil welding process that involves the formation of a fusion weld lens with a solid-state diffusion bonding zone. This welding process is used to weld electrode foils and internal connecting leads together for use in prismatic battery cells. The battery cells can then be used in batteries installed in electric or hybrid electric vehicles.

[0032] As used herein, the term "vehicle" is not limited to automobiles. While the technology presented herein is mainly described in connection with electric and hybrid electric vehicles and, in particular, batteries, the technology is not limited to electric and hybrid electric vehicles and batteries.The concepts can be used in a variety of applications, such as in conjunction with components used in motorcycles, mopeds, locomotives, aircraft, watercraft and other vehicles, as well as in other applications that use batteries, such as portable power plants, like those used to supply energy to remote construction sites, emergency power supplies and permanent power plants connected to buildings and equipment, all of which can be powered, for example, by solar or wind-powered generator systems, power grids and fuel-based power generators, such as gasoline, propane, kerosene or diesel generators, as well as in additional applications where several layers of relatively thin film need to be welded together.

[0033] Fig. Figure 1 illustrates a vehicle 100 with a drive system 120. The drive system 120 generally comprises an electric motor 124 and a secondary battery 126 for supplying energy to the electric motor 124. Furthermore, in many embodiments, the drive system 120 includes an inverter 128 for converting energy from DC (direct current), as supplied by the battery 126, to AC (alternating current), as used by the electric motor 124. The inverter 128 can be contained in a power electronics module 130, which includes, for example, transistors and diodes for switching the energy from DC to AC and vice versa.

[0034] A controller 132 is connected to the inverter 128 and is programmed to control and manage the operation of the electric motor 124 and the associated hardware, including the inverter 128. The electric motor 124 is connected to a gearbox (drive unit) 136 and a drive line 138, which transmits mechanical energy and rotation to the wheels 140 of the vehicle 100. The controller 132 has one or more processors and tangible, non-volatile memory 134.

[0035] Referring again to the electric motor 124, the electric motor 124, which is powered by the battery 126, has a stator 142 and a rotor 144 located inside the stator 142. The stator 142 is the stationary part of the electric motor 124. The stator 142 provides a rotating magnetic field with which the stationary magnetic field of the rotor 144 attempts to align, causing the rotor 144 to rotate, which can be referred to as the "motor operation" mode. In other applications, the rotating field of the rotor 144 (as caused by physical rotation) generates an electric current in the stator 142—this operating mode is referred to as "generation," and the electric motor 124 used in this way is called a generator. In traction motor vehicle applications, motor operation provides motion to the vehicle 100.The generation mode captures some of the energy recovered from braking when the vehicle is in the process of stopping and stores it back in the vehicle battery.

[0036] It will be directed to the Fig. 2A and Fig. Reference is made to Figure 2B, which illustrates an example of a secondary battery 126 for supplying energy to an electric or hybrid electric vehicle 100, such as the one described in Fig. 1 illustrated electric vehicle 100. As noted above, secondary batteries are understood to be rechargeable batteries that can be discharged when a load is applied and recharged when an external energy source is applied. Referring to the Fig. 2A and Fig. Figure 2B illustrates that the battery 126 is connected to a load 148, such as the electric motor 124. Other loads 148 include various systems in the vehicle, such as climate control systems and infotainment systems. The battery 126 has one or more battery cells 150 that are assembled together. During discharge, when a load is applied to the battery 126, Li + Ions move from the anode 158 to the cathode 156 through the separator 160 via the electrolyte 162. Equivalent electrons e- move through the circuit 146 from the cathode 156 to the anode 158, thereby supplying energy to the load 124. During charging, when an external voltage is applied, Li + -Ions from the cathode 156 to the anode 158 via the electrolyte 162 through the separator 160 and can be deposited in the anode 158.

[0037] Each battery cell contains 150 cells, such as those in Fig. As illustrated in Figure 2B, the device generally has two electrodes. The first electrode is a cathode electrode 151, which has a cathode current collector 152 and a cathode 156 arranged on the cathode current collector 152. The second electrode is an anode electrode 153, which has an anode current collector 154 and an anode 158 arranged on the anode current collector 154. Each current collector 152, 154 has a foil tab 164, 166. The foil tabs 164, 166 can be formed integrally with the current collector 152, 154 by cutting or punching each current collector 152, 154, which has the foil tab 164, 166, from a larger foil sheet. Alternatively, the foil tabs 164, 166 can be welded onto the pantographs 152, 154 after the pantographs 152, 154 have been punched or trimmed.Each battery cell 150 also has one or more separators 160 positioned between the cathode 156 and the anode 158, and an electrolyte 162, such as a liquid electrolyte or a solid electrolyte, which is in close contact with the surface of the separator 160, the cathode 156 and the anode 158.

[0038] While the illustrated battery cell 150 of Fig. 2B comprises an anode electrode 153 and cathode electrodes 151 and one or more anode electrodes 153. In alternative embodiments, the battery cell 150 can have one or more cathode electrodes 151 and two or more anode electrodes 153. Furthermore, in embodiments, a cathode 156 can be deposited on one or both sides of the cathode current collector 152 in a given cathode electrode 151, and an anode 158 can be deposited on one or both sides of the anode current collector 154 in a given anode electrode 153.

[0039] Fig. Figure 3 illustrates an embodiment in which several cathode electrodes 151 and anode electrodes 153 are present and a separator is provided between the cathode electrodes 151 and anode electrodes 153. While only three cathode electrodes 151 and three anode electrodes 153 are illustrated, the number of cathode electrodes 151 can range from 1 to 300, including all values ​​and ranges therein, such as 2 to 150, 30 to 60, etc., and the number of anode electrodes 153 can range from 1 to 300, including all values ​​and ranges therein, such as 2 to 150, 30 to 60, etc. Figure 3 illustrates an embodiment in which several cathode electrodes 151 and anode electrodes 153 are present, including all values ​​and ranges therein, such as 2 to 150, 30 to 60, etc. Fig. 3 a stacked battery cell 150, wherein the separator 160 is ribbon-shaped and z-folded or nested between each cathode electrode 151 and anode electrode 153. Fig. Figure 4 illustrates an embodiment in which the cathode electrode 151, the anode electrode 153, and the separators 160 are wound into a jelly-roll configuration that is flattened. Two separators 160 are used to separate the cathode electrode 151 and the anode electrode 153. Either configuration, i.e., jelly-roll or stacked, can be used in the prismatic battery cell.

[0040] The battery cell 150 has a housing 170 that is relatively rigid and generally has a cuboid configuration, as shown in Fig. 2B illustrates. With reference to Fig. In Figure 5, the foil tabs 164 of the cathode electrodes 151 are welded together to form a cathode foil stack 182, and the foil tabs 166 of the anode electrodes 153 are welded together to form an anode foil stack 184. While one cathode foil stack 182 and one anode foil stack 184 are shown, multiple cathode foil stacks 182 and multiple anode foil stacks 184 may be present. While it is illustrated that the foil tabs 164, 166 project from the battery cell 150 in the same direction, in additional or alternative embodiments the foil stacks 182, 184 may project from the battery cell 150 in different directions, such as from opposite directions. Additionally, the cathode foil stack 182 has internal cathode connection lines 172, 174 and the anode foil stack 184 has internal anode connection lines 176, 178.While two internal connecting lines 172, 174 for the cathode foil tabs 164 and two internal connecting lines 176, 178 for the anode foil tabs 166 in . Fig. As illustrated in Figure 5, alternatively a single internal connection line can be used for each of the slide stacks 182, 184.

[0041] The cathode current collector 152 and the anode current collector 154 are made of conductive materials. In embodiments, the cathode current collector 152 comprises aluminum. Alternatively or additionally, the cathode current collector 152 can comprise copper-clad aluminum and stainless steel. The anode current collector 154 can comprise one or more components of copper, nickel, stainless steel, and titanium. The current collectors 152 and 154 are illustrated as being in the form of foil plates; however, it is understood that other forms, such as mesh plates, are possible. In embodiments, a foil cathode current collector 152 and a foil anode current collector 154 are gas-tight. The cathode current collector 152 and the foil tab 164 extending from it have a thickness in the range of 5 micrometers to 50 micrometers, including all values ​​and ranges therein, such as the range of 5 micrometers to 25 micrometers.The anode current collector 154 and the foil tab 166 extending from it have a thickness in the range of 4 micrometers to 50 micrometers, including all values ​​and ranges therein, such as in the range of 4 micrometers to 25 micrometers or 13 micrometers.

[0042] In embodiments, the internal connecting lines 172, 174, 176, 178, contained in the foil stacks 182, 184, comprise aluminum. Alternatively or additionally, the internal connecting lines 172, 174, 176, 178 comprise at least one or more components of copper, copper-clad aluminum, stainless steel, nickel, and titanium. In certain embodiments, the internal connecting lines 172, 174, 176, 178 comprise aluminum. The internal connecting lines 172, 174, 176, 178 have a thickness ranging from 0.5 millimeters to 5 millimeters, including all values ​​and increments therein.

[0043] Cathode 156 features an active material that is a source of lithium ions (Li). +) provides and can be subjected to reversible insertion or deposition of lithium ions, which determines, for example, the capacity and average voltage of a battery. In embodiments, the active material comprises at least one of lithium iron phosphate (LFP), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium manganese iron phosphate (LMFP), and lithium nickel manganese cobalt oxide (LiNiMnCoO2). The cathode 156 has a thickness in the range of 80 micrometers to 500 micrometers, including all values ​​and ranges therein, such as approximately 110 micrometers.The cathode electrode 151, which has both the cathode current collector 152 and the cathode 156, has a thickness in the range of 85 micrometers to 550 micrometers, including all values ​​and ranges therein, when coated on one side of the cathode current collector 152, and has a thickness in the range of 165 micrometers to 1050 micrometers, including all values ​​and ranges therein, when coated on both sides, for a double-sided cathode electrode 151, such as in the range of 205 micrometers to 500 micrometers.

[0044] The anode 158 comprises materials that can be subjected to reversible insertion or intercalation of lithium ions at a lower electrochemical potential than the material of the cathode 156, such that an electrochemical potential difference exists between the anode 158 and the cathode 156. The anode material can comprise one or more of the following: lithium metal; lithium alloys, such as lithium silicon alloy, lithium aluminum alloy, lithium indium alloy, lithium titanate, and lithium tin alloy; carbon-based materials, such as graphite, activated carbon, carbon black, and graphene; silicon; silicon-based alloys; silicon oxide; silicon-based composite materials; tin oxide; aluminum; indium; zinc; germanium; and titanium oxide; as well as any combination thereof. In embodiments, the anode 158 has a thickness in the range of 50 micrometers to 150 micrometers, including all values ​​and ranges therein.When coated on the anode current collector 154, the anode electrode 153 has a thickness in the range of 54 micrometers to 200 micrometers, including all values ​​and ranges therein. When the anode 158 is coated on both sides of the anode current collector 154, the anode electrode 153 has a thickness in the range of 58 micrometers to 250 micrometers, including all values ​​and ranges therein.

[0045] The separator 160 is a porous, electrically insulating material that prevents the cathode 156 and the anode 158 from touching the circuit and potentially short-circuiting. The separator 160 is arranged between, or at least partially enclosed by, the cathode 156 and the anode 158, allowing the passage of lithium ions and the electrolyte 162 through the pores of the separator 160. The separator 160 can comprise one or more of a composite material, a polymer material, and a nonwoven material. In embodiments, the separator 160 comprises at least one of polyethylene, polypropylene, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride. Additionally, the separator 160 can be filled, i.e., it can contain fillers dispersed within it, the filler being a material such as glass fiber.In additional or alternative embodiments, the separator 160 can have at least one heat-stable, porous polymer coating and one ceramic coating, such as an aluminum oxide coating. The coating is arranged on one or more surfaces of a porous polymer film, the polymer film being selected from at least one of polyethylene and polypropylene. The separator 160 can have one or more layers, each layer being formed from one or more of the aforementioned materials. The separator 160 can take the form of a film or a mesh, such as a woven mesh or a slit film. In embodiments, the separator 160 has a thickness in the range of 4 micrometers to 25 micrometers, including all values ​​and ranges therein.

[0046] The electrolyte 162 provides a medium between the cathode 156 and the anode 158 through which lithium ions and the electrolyte move. The medium can be a liquid, a gel, or a solid and must be capable of conducting the lithium ions between the cathode 156 and the anode 158. The electrolyte 162 penetrates the pores of the porous separator 160 and wets or otherwise contacts the surfaces of the cathode 156, the anode 158, and the separator 160. In embodiments, the electrolyte 162 comprises one or more lithium salts dissolved in a non-aqueous organic solvent.The lithium salts may contain one or more of the following: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2) (LiBOB), lithium difluorooxalatoborate (LiBF2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonylimide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (LiSFI), lithium (triethylene glycol dimethyl ether)bis(trifluoromethanesulfonyl)imide (Li(G3)(TFSI)) and Lithium bis(trifluoromethanesulfonyl)azidide (LiTFSA).

[0047] The non-aqueous aprotic organic solvent contains one or more of various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylic acid esters (e.g., methyl formate, methyl acetate, methyl propionate), g-lactones (e.g., g-butyrolactone, g-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane).

[0048] Furthermore, electrolyte 162 may contain a number of additives, such as, but not limited to, vinyl carbonate, vinylethylene carbonate, propanesulfonate, 1,3,2-dioxathiolane-2,2-dioxide (DTD), LiPF2O2, and combinations thereof. Other additives may include diluents that do not coordinate with lithium ions but can reduce the viscosity of electrolyte 162, such as bis(2,2,2-trifluoroethyl) ether (BTFE), and flame retardants, such as triethyl phosphate.

[0049] With reference to Fig. Figure 6 illustrates a general method 600 for connecting foil tabs 200, such as foil tabs 164, 166, and the internal connecting leads 202, 204, such as internal connecting leads 172, 174, 176, 178. The method 600, in block 602, involves clamping foil tabs 200, such as those of at least one of the cathode current collectors 156 and anode current collector 158 described above, together with one or more connecting leads 202, 204, as shown in Figure 6. Fig. 7, Fig. 8A, Fig. 8B, Fig. 9A and Fig. Figure 9B illustrates how to form a stack of foils. As illustrated, the welded joints formed can be edge joints, overlap joints, or overlap joints. Fig. 8A and Fig. Figure 9A illustrates embodiments in which internal connecting lines 202, 204 are clamped adjacent to the foil tabs 200 and provide the outer surfaces 210, 212 of the foil stack 208. Fig. 8B and Fig. Figure 9B illustrates embodiments in which a single internal connecting line 204 is contained within the film stack 208. Alternatively, the internal connecting lines 202, 204 can be placed between the film flaps 200, and the outermost film flaps 200 provide the outer surfaces 210, 212 of the film stack 208.

[0050] The terminals 216, 218, 220 are generally aligned parallel to the orientation of the film tabs 200 and the internal connecting leads 202, 204 in the film stack 208. A first terminal 216 is positioned adjacent to the first outer surface 212, which is opposite the second outer surface 210. In embodiments such as in Fig. 7, Fig. 8A, Fig. 8B, Fig. 9A, Fig. As illustrated in Figure 9B, a second clamp 218 is placed adjacent to the second outer surface 210. In further embodiments, where the light beam 224 emitted by the laser 226 intersects a plane formed by the second clamp 218, as in the case of overlap connections and overlap joints, as in Fig. 8A, Fig. 8B, Fig. 9A and Fig. As illustrated in Figure 9B, the second clamp 218 is placed adjacent to the expected location on the circumference of the point of the light beam 224 on the incident surface 228 of the foil stack 208. In additional or alternative embodiments, the at least one clamp 218 is placed adjacent to the expected melting limit 230, i.e., the boundary of the melting zone where the liquid and solid phases of the metal coexist, and on the solid-phase side of the melting limit. In still further embodiments, as in the case of Figure 9B, the clamp 218 is placed adjacent to the expected melting limit 230, i.e., the boundary of the melting zone where the liquid and solid phases of the metal coexist, and on the solid-phase side of the melting limit. Fig. 8A and Fig. In the overlap connections illustrated in Figure 8B, a third clamp 220 is placed on the other side of the expected location on the circumference of the laser beam point 224 on the incidence surface 228 of the foil stack 208. Fig. 9A and Fig. In 9B, where the weld joint 250 is an overlap joint, only one clamp 218 can be used on the second outer surface 210. The clamps 216, 218, and 220 exert pressure against the foil stack 208 and the internal connecting lines 202 and 204. The pressure exerted by the clamps 216, 218, and 220 is in the range of 0 megapascals (MPa) (0 pounds per square inch) to 3.45 megapascals (MPa) (500 pounds per square inch), including all values ​​and ranges within this range, such as 0.1 megapascals to 2.5 megapascals, 1 megapascal to 2 megapascals, etc.

[0051] In block 604, a light beam 224 is emitted from a laser 226 onto an incidence surface 228 of the foil stack 208, such as the second outer surface 212. While the images illustrate that the laser axis 232 is generally oriented orthogonally to the incidence surface 228, the laser axis can be oriented at an angle 234 of more than 15 degrees relative to the incidence surface 228, including all values ​​and ranges from 15 degrees to 90 degrees.

[0052] Additionally, the laser 226 generally emits a light beam 224 in a pattern of core 240 and ring 240, as in Fig. Figure 10 illustrates this. In embodiments, the power at core 240 is in the range of 30 percent to 70 percent of the total power emitted by laser 226, and the power in ring 242 is in the range of 30 percent to 70 percent of the total power emitted by laser 226. In preferred embodiments, more power is present in core 240 than in ring 242. In embodiments, the laser power at core 240 is in the range of 1,000 W to 2,000 W, including all values ​​and ranges therein, depending on the materials used and the material thickness, and the laser power in ring 242 is in the range of 500 W to 1,500 W, including all values ​​and ranges therein. Too low a laser core power results in a minimal solid-state weld depth, and too high a laser core power leads to excessive penetration and a reduced solid-state weld depth, ultimately weakening the weld strength.The ratio of the core diameter 244 to the ring diameter 244 is in the range of 1:1.5 to 1:4, including all values ​​and ranges therein. Furthermore, in embodiments, the light beam 224 is moved across the second outer surface 210 and the incidence surface 228 to provide a welding speed in the range of 5 millimeters per second to 150 millimeters per second, including all values ​​and ranges therein, such as 10 millimeters per second to 90 millimeters per second, 50 millimeters per second, etc. Herein, the welding speed is understood to be the rate at which the laser moves across the workpiece.

[0053] Furthermore, in embodiments, the laser energy can be adjusted by shaping the light beam 224 to emit light around half the ring in an arc on only one side of the core, as in Fig. 12A and Fig. Figure 12B illustrates this. The arc can extend from 10 percent to 80 percent of ring 242. Fig. Figure 12B illustrates the power profile A of the light beam 224, with the power percentage shown on the vertical y-axis and the distance shown on the horizontal x-axis, where C is the center of the beam. The laser beam 224 can be shaped using one or more diffracting or reflecting elements. Furthermore, in additional or alternative embodiments, the laser 226 and the light beam 224 emitted by it can be oscillated, applying unequal amounts of laser energy to increase the diffusion connection, as shown in Fig. 13A and Fig. Figure 13B illustrates this. Laser oscillations can be facilitated by moving the laser itself or by moving the laser optics relative to the laser and the weld 250. Fig. Figure 13A illustrates one embodiment of an oscillation pattern 270. Other oscillation patterns can also be used. Fig. Figure 13B illustrates the power profile A of the laser oscillation of the oscillation pattern of Fig. 13A, where the power percentage is illustrated on the vertical y-axis and the distance is illustrated on the horizontal x-axis, with C being the center of the oscillation pattern. Beam shaping in the manner described above can be used when welding an overlap joint, wherein the foil stack 208 does not extend over both internal connecting lines 202, 204, as in Fig. 9 illustrates.

[0054] With renewed reference to Fig. 6, Fig. 7, Fig. 8, Fig. 9 to Fig. In block 606, a weld joint 250 is formed, which has a weld lens 252 formed by the core 240 of the laser beam 224 together with a solid-state diffusion bond zone 254 formed around a section of the weld lens 252 by the ring 242 of the light beam 224. The weld lens 250 is a pool of molten metal, generally formed by the core of the light 224 emitted by the laser 226, which solidifies into a lens shape upon cooling. The weld lens 252 extends over the multitude of foil tabs 200 and is thicker than the thickness 258 of the foil tabs 200 in the foil stack 208. Furthermore, the weld lens 252 extends into the adjacent internal connecting lines 202, 204. The depth 260 of the weld lens 252 relative to the incidence surface 228 is in the range of 250 micrometers to 2,200 micrometers, including all values ​​and ranges therein.The diffusion bonding zone 254 is present in the heat-affected zone (HAZ). In the diffusion bonding zone 254, atoms migrate from a first surface to adjacent surfaces due to the pressure provided by the clamps 216, 218, 220 and heat generated by the light beam 224 emitted by the laser 226. Thus, the metal does not melt in the diffusion bonding zone 254. The diffusion bonding zone 254 extends over the foil tabs 200 around at least one section of the weld lens 252. The depth 262 of the diffusion bonding zone 220 relative to the incidence surface 204 is in the range of 300 micrometers to 2,600 micrometers, including all values ​​and regions within this range. In block 608, the foil stack 208, which is connected to the internal connecting lines 202, 204, is removed from terminals 216, 218, 220. Procedure 600 can then be repeated for the other foil stack.Additionally, the resulting welded joints 250 exhibit a tensile strength in the range of 230 Newtons to 600 Newtons, including all values ​​and ranges therein, when 40 foil flaps 200 or more are present.

[0055] A method for forming a battery cell 150 is described in Fig. 13 and with further reference to the Fig. 7, Fig. 8, Fig. 9, Fig. 10 to Fig. Figure 11 illustrates this. Method 1300, in block 1302, features the arrangement of at least one cathode electrode 151, at least one anode electrode 153, and at least one separator 160 in a stacked or jelly-roll configuration. In block 1304, the foil tabs 200 of the cathode electrodes 151 and the anode electrodes 153 are connected to the internal connecting leads 202, 204 of the cathode electrodes 151 and the anode electrodes 153, as shown above with reference to Fig. The process described in section 600 is welded. The jelly-roll or stacked cathode electrodes 151, anode electrodes 153, and separators 160, including the welded internal connecting leads 202 and 204, are placed in the housing 170 at block 1306. At block 1308, internal connecting leads 202 and 204 are connected to external terminals extending from the battery housing 170. At block 1310, the battery housing 170 is sealed. At block 1320, the electrolyte 162 is added to the housing 170 if it was not already present as a solid electrolyte in the jelly-roll or stacked layers.

[0056] A comparative example was produced in which 40 layers of aluminum foil (simulating the foil tabs 164, 200) with a thickness of 480 micrometers were joined to 2.5 mm aluminum sheet (simulating the internal connecting leads) using a 37 mm overlap joint. The joint was formed using ultrasound and a laser. A sample was then produced according to the procedure described herein using 40 layers of aluminum cathode current collectors 152 with extending foil tabs 164, each with a thickness of 480 micrometers, joined to 2.5 mm aluminum sheet using a 45 mm edge weld, as shown in Fig. Figure 7 illustrates the results. Fig. Figure 14 illustrates the breaking load, measured in Newtons, on the primary vertical y-axis. Beam A is the comparative example, breaking at 227.5 Newtons, and Beam B, produced according to the present description, breaks at 548.33 Newtons. The strength of the two welds was compared. Newtons per millimeter are illustrated on the secondary vertical y-axis. The breaking strength for the welds was 227.5 Newtons per 37 millimeters (Beam C) and 548.22 Newtons per 45 millimeters (Beam D); averaging 6.15 Newtons per millimeter and 12.19 Newtons per millimeter, respectively.

[0057] Several tensile strength tests were performed using different core / ring power ratios with a total emitted laser power of 1.7 kW to join 2.5 mm aluminum sheets to 12 µm thick aluminum foils. The welding speed was 50 mm per second, and the core-to-ring power ratio was adjusted in 10 percent increments between 20 percent core power of the total power emitted by the laser and 70 percent core power of the total power emitted by the laser. The relationship between the combined fusion weld lens depth and diffusion bond depth and the tensile strength test is shown in Fig. Figure 15 shows the penetration depth of the weld lens in micrometers. This is illustrated on the primary vertical, y'-axis in the lower section of the graph bars, and the solid diffusion bond depth, also measured in micrometers, is illustrated on the primary vertical, y'-axis in the upper section of the graph bars. The tensile strength, measured in Newtons, is illustrated by the scatter plot line A on the secondary vertical, y''-axis.

[0058] It was found that using 60% of the laser power in the core and 40% in the ring resulted in the maximum depth of both the weld lens and the diffusion bond, leading to the highest weld strength. Using 20% ​​power in the core resulted in a minimum solid bond depth in the joint, resulting in the weakest strength. Conversely, using 70% power in the core resulted in excessive penetration but a reduced solid bond depth, ultimately decreasing the weld strength compared to 60% power. Weld failure in weld 1500 occurred at the foil diffusion bond 1502 and the weld lens 1504, as shown in Fig. 16A illustrates. Fig. Figure 16B shows the successful diffusion bonding of foils to aluminum sheets 1506, as evidenced by the presence of foils 1508 that remained attached to the aluminum sheet after the tensile test. Upon examination of the foils 1508 that were pulled from the weld joint, it is evident that they have been securely diffusion-bonded to one another, as shown in Fig. 17 illustrated.

[0059] The resistance before and after the tensile test of the specimen produced according to this description was measured using the four-wire method for measuring resistance. As described in Fig.As illustrated in Figure 18, it was observed in both the tensile test specimens before (B) and after (A) that the resistance, measured in milliohms and shown on the vertical y-axis, decreased when the percentage of applied core power reached 70 percent, with the resistance then beginning to increase again, as illustrated on the horizontal x-axis. Additionally, it was found that the resistance after the fracture (A) was higher than the resistance before (B) of the tensile test. This indicates that the diffusion bond improved the electrical conductivity of the welded joints, as the fracture occurred between the weld nugget and the diffusion-bonded area of ​​the foils.

[0060] The welding process described herein, and the components assembled by this process, offer several advantages. These advantages include improved performance of sheet metal welds, including improved weld joint strength. They also include improved conductivity of the welded joints. Furthermore, they result in reduced porosity and separation between the sheets.

[0061] The description provided here is merely exemplary, and variations that do not deviate from the core of the description are to be considered within its scope. Such variations should not be regarded as a departure from the spirit and scope of the description provided.

Claims

[1] Battery cell, comprising: a stack of foil, wherein the stack of foil has a plurality of foil tabs, each extending from a current collector and at least one internal connecting line; and a welded joint formed between the plurality of film flaps and the at least one connecting line in the film stack, wherein a section of the welded joint has a weld lens extending over the plurality of film flaps into the internal connecting line, and the remainder of the welded joint has a diffusion bonding zone, wherein the diffusion bonding zone extends around at least one section of the weld lens. [2] Battery cell according to claim 1, wherein the weld lens has a depth in the range of 250 micrometers to 2,200 micrometers relative to an incidence surface, and the diffusion bonding zone has a depth in the range of 300 micrometers to 2,600 micrometers relative to the incidence surface. [3] Battery cell according to claim 1, wherein at least one connection line has a first connection line and a second connection line, wherein the first connection line is configured to provide a first outer surface of the film stack and the second connection line is configured to provide a second outer surface of the film stack. [4] Battery cell according to claim 1, wherein the plurality of foil tabs comprises two to 300 foils. [5] Battery cell according to claim 1, wherein the internal connecting leads have a thickness in the range of 0.5 millimeters to 5 millimeters. [6] Battery cell according to claim 5, wherein the plurality of foil tabs comprises two to 300 foils and the current collector is a cathode current collector and each cathode current collector has a thickness in the range of 5 micrometers to 50 micrometers. [7] Battery cell according to claim 6, wherein the cathode current collector has aluminium and the internal connecting line has aluminium. [8] Battery cell according to claim 5, wherein the plurality of foil tabs comprises two to 300 foils and the current collector is an anode current collector and each anode current collector has a thickness in the range of 4 micrometers to 50 micrometers. [9] Battery cell according to claim 8, wherein the anode current collector has copper and the internal connecting line has copper. [10] Method for welding electrode foils, comprising: Clamping a stack of foils together with at least two clamps, wherein the stack of foils has a plurality of foil tabs, each extending from a current collector and extend to at least one internal connecting line, wherein a first of the two terminals is positioned on a first outer side of the foil stack and a second of the at least two terminals is positioned on a second outer side of the foil stack; Applying pressure to the stack of foils with the clamps; Emitting a light beam from a laser onto the second outer surface of the foil stack, wherein the light beam has a total power of emitted light and light in a core and ring pattern emitted, with the power in the core ranging from 30 percent to 70 percent of the total power of emitted light and the power in the ring ranging from 30 percent to 70 percent of the total power of emitted light; and Forming a weld joint, wherein a section of the weld joint has a weld lens formed at least partially by the core of the laser beam, and the remainder of the weld joint has a diffusion bond zone formed at least partially by the ring of the laser beam.

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