Method for consolidating multilayer foil using hot pressing

Abstract

The present disclosure provides a method for consolidating a foil stack. The method includes assembling foils of an electrode stack in a battery cell to form a combined foil stack. In addition, the method includes hot pressing the combined foil stack using a heated press die to form a consolidated foil stack. Further, the method includes laser welding the consolidated foil stack to the terminal lead using a laser welder.

Description

Technical Field

[0001] The present disclosure relates to electrode stacks in battery cells, and more particularly to consolidating electrode sheets within the electrode stack. Background Art

[0002] Battery cells, such as prismatic cells, typically include multiple electrode stacks. Each electrode stack includes anode and cathode electrode sheets extending from the stack. The electrode sheets of the electrode stack are welded and connected to terminal leads or current collectors. Current collectors are metal plates that consolidate the current generated by the electrode stack and transmit it to the terminals on the battery cell. When welding the electrode sheets, surface contamination on the electrode sheets can cause gas release, forming air cavities. These air cavities, combined with tension caused by shrinkage during solidification, can cause the electrode sheets at the melt boundary to detach.

[0003] Although prior art methods and systems attempt to minimize electrode sheet shedding at the fusion boundary and may achieve their intended purpose, a new and improved method for reducing electrode sheet shedding is still needed. Summary of the Invention

[0004] According to several aspects of the present disclosure, a method for consolidating a foil stack is provided. The method includes combining foils from an electrode stack in a battery cell to form a combined foil stack. Furthermore, the method includes hot pressing the combined foil stack using a heated press die to form a consolidated foil stack. Furthermore, the method includes laser welding the consolidated foil stack to a terminal lead using a laser welder.

[0005] According to another aspect of the present disclosure, the method includes hot pressing a foil formed of at least one of copper or aluminum.

[0006] According to another aspect of the present disclosure, the method includes heating the combined foil stack to a temperature between 350 Kelvin and 680 Kelvin and maintaining the temperature for 5 seconds to 30 minutes.

[0007] According to another aspect of the present disclosure, the method includes using an induction heated die when hot pressing the combined foil stack.

[0008] According to another aspect of the present disclosure, the method includes using a resistively heated die when hot pressing the combined foil stack.

[0009] According to another aspect of the present disclosure, the method includes forming at least one indentation feature in the combined foil stack with a heated press die while hot pressing the combined foil stack.

[0010] According to another aspect of the present disclosure, the method includes forming at least one wavy feature in the combined foil stack with a heated die while hot pressing the combined foil stack.

[0011] According to another aspect of the present disclosure, the method includes forming at least one rib feature in the combined foil stack with a heated press die while hot pressing the combined foil stack.

[0012] According to another aspect of the present disclosure, the method includes using a high frequency oscillating laser when laser welding the combined foil stack.

[0013] According to another aspect of the present disclosure, the method further includes cooling at least one of a portion of a jig or a portion of a sub-jig configured to hold the electrode stack during hot pressing of the combined foil stack.

[0014] According to another aspect of the present disclosure, the method includes using a Peltier plate when cooling at least a portion of the fixture.

[0015] According to another aspect of the present disclosure, the method includes using cooling channels in the sub-jig when cooling at least a portion of the jig.

[0016] According to several aspects of the present disclosure, a method for consolidating a foil stack is provided. The method includes combining foils from an electrode stack in a battery cell to form a combined foil stack. The method also includes clamping the combined foil stack to secure it in place. The electrode stack is supported by a fixture, and the combined foil stack is supported by a sub-fixture. The method also includes hot pressing the combined foil stack using a heated die to form a consolidated foil stack. Furthermore, the method includes laser welding the consolidated foil stack to a terminal lead using a laser welder.

[0017] According to another aspect of the present disclosure, the method includes heating the combined foil stack to a temperature between 350 Kelvin and 680 Kelvin and maintaining the temperature for 5 seconds to 30 minutes while hot pressing the combined foil stack.

[0018] According to another aspect of the present disclosure, the method includes using a press die that incorporates an induction coil into a fixture that compresses the combined foil stack while hot pressing the combined foil stack. The induction coil heats the combined foil stack.

[0019] According to another aspect of the present disclosure, the method further includes cooling at least one of a portion of a jig or a portion of a sub-jig configured to hold the electrode stack during hot pressing of the combined foil stack.

[0020] According to several aspects of the present disclosure, a method for consolidating a foil stack is provided. The method includes combining foils from an electrode stack in a battery cell to form a combined foil stack. The foils are formed from copper or aluminum. The method includes clamping the combined foil stack to secure the foil stack in place. The electrode stack is supported by a fixture, and the combined foil stack is supported by a sub-fixture. The method includes hot pressing the combined foil stack using a heated press die to form a consolidated foil stack. The method includes using a cooling system to cool at least a portion of the consolidated foil stack, wherein the cooling system is integrated into the sub-fixture. The method includes laser welding the consolidated foil stack to a terminal lead using a high-frequency oscillation laser welder.

[0021] According to another aspect of the present disclosure, the method includes using a Peltier plate when cooling at least a portion of the fixture.

[0022] According to another aspect of the present disclosure, the method includes heating the combined foil stack to a temperature between 350 Kelvin and 680 Kelvin and maintaining the temperature for 5 seconds to 30 minutes while hot pressing the combined foil stack.

[0023] According to another aspect of the present disclosure, the method includes using cooling channels in the sub-jig when cooling at least a portion of the jig.

[0024] Further areas of applicability will become apparent from the following detailed description provided herein.It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0025] The above features and advantages and other features and advantages of the presently disclosed systems and methods are readily apparent from the detailed description, including the claims and examples, when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0027] Figure 1 is a perspective view illustrating an example of a vehicle including a battery pack having a plurality of battery cells according to the present disclosure.

[0028] Figure 2A The present invention is provided in the following manner Figure 1 A perspective view of a battery cell within a battery pack is shown, wherein the battery cell includes at least one electrode stack having a plurality of electrode tabs welded to a current collector.

[0029] Figure 2B According to the present disclosure Figure 2A A partial cross-sectional view of a battery cell is shown, illustrating the layers in a single electrode stack and a set of anode and cathode electrode sheets.

[0030] Figure 3 is a flow chart illustrating a method of laser welding anode and cathode electrode sheets to current collectors using hot pressing according to the present disclosure.

[0031] Figure 4 It shows that according to the present disclosure Figure 2A A perspective view of an electrode stack and a combined foil stack is shown with a clamp and sub-clamp supporting the electrode stack and the combined foil stack.

[0032] Figure 5 It shows that according to the present disclosure Figure 4 A perspective view of an electrode stack and a built-up foil stack is shown, with a press die hot pressing the built-up foil stack.

[0033] Figure 6 It shows that according to the present disclosure Figure 4 A perspective view of an electrode stack and a consolidated foil stack obtained by hot pressing the combined foil stacks is shown.

[0034] Figure 7 It shows that according to the present disclosure Figure 4 An isometric perspective view of the electrode stack and consolidated foil stack is shown.

[0035] Figure 8 is a perspective view showing a combined foil stack and a pressing die for hot pressing the combined foil stack according to the present disclosure.

[0036] Figure 9 It shows that according to the present disclosure Figure 8 A perspective view of the consolidated foil stack is shown after hot pressing the combined foil stack.

[0037] Figure 10 is a perspective view illustrating a combined foil stack and a press die for hot pressing the combined foil stack according to the present disclosure, wherein the press die is configured to create features in the resulting consolidated foil stack.

[0038] Figure 11 It shows that according to the present disclosure Figure 10 A perspective view of a consolidated foil stack produced by hot pressing a combined foil stack is shown, wherein features produced in the consolidated foil stack include indentation features.

[0039] Figure 12 It shows that according to the present disclosure Figure 10 A perspective view of a consolidated foil stack produced by hot pressing a combined foil stack is shown, wherein features produced in the consolidated foil stack include wavy features.

[0040] Figure 13 It shows that according to the present disclosure Figure 10A perspective view of a consolidated foil stack produced by hot pressing a combined foil stack is shown, wherein features produced in the consolidated foil stack include rib features.

[0041] Figure 14 is a perspective view showing a built-up foil stack supported by a clamp and a sub-clamp having trimming features for trimming ends of the built-up foil stack according to the present disclosure.

[0042] Figure 15 is a diagram showing the use of the present disclosure as Figure 14 A perspective view of a consolidated foil stack with trimmed features shown.

[0043] Figure 16 is a perspective view showing an electrode stack and a combined foil stack supported by a jig and a sub-jig including a cooling system having cooling channels supplied by a coolant according to the present disclosure.

[0044] Figure 17 is a perspective view showing an electrode stack and a combined foil stack supported by a clamp and a sub-clamp including a cooling system with Peltier plates according to the present disclosure.

[0045] Figure 18 is a perspective view showing a consolidated foil stack welded to a terminal lead, wherein the resulting weld is a butt weld, in accordance with the present disclosure.

[0046] Figure 19 is a perspective view showing a consolidated foil stack welded to a terminal lead according to the present disclosure, wherein the resulting weld is a lap weld located a distance from the end of the consolidated foil stack.

[0047] Figure 20 is a perspective view showing a consolidated foil stack welded to a terminal lead according to the present disclosure, wherein the resulting weld is a lap weld, with the weld location being at an end of the consolidated foil stack.

[0048] Figure 21 is a perspective view showing two consolidated foil stacks according to the present disclosure, each supported by a fixture and a sub-fixture having Peltier plates, wherein one Peltier plate heats the first consolidated foil stack and a second Peltier plate cools the second consolidated foil stack during the welding process. DETAILED DESCRIPTION

[0049] Reference will now be made in detail to several embodiments of the present disclosure as illustrated in the accompanying drawings. Whenever possible, the same or similar reference numerals are used in the drawings and the description to refer to the same or similar parts or steps. The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses.

[0050] refer to Figure 1 , shows a perspective view of a vehicle 10 having a battery pack 12 according to the present disclosure. The battery pack 12 is shown together with an exemplary vehicle 10. The vehicle 10 is an electric vehicle or a hybrid vehicle having wheels 11 driven by a motor / inverter 13. The motor / inverter 13 receives power from the battery pack 12. Although the vehicle 10 is shown as a passenger road vehicle, it should be understood that the battery pack 12 can be used with various other types of vehicles. For example, the battery pack 12 can be used in a marine vehicle (such as a ship) or an aerial vehicle (such as a drone or a passenger aircraft). In addition, the battery pack 12 can be used as a stationary power source that is separate and independent from the vehicle. The battery pack 12 includes a housing 14 for supporting a plurality of battery cells 18. The battery pack 12 can have fifty or more battery cells 18.

[0051] Now refer to Figure 2A , showing an example according to one aspect of the present disclosure Figure 1 A perspective view of a battery cell 18 shown disposed within a battery pack 12. Each battery cell 18 has an outer shell or housing (not shown) and a plurality of electrode stacks 22. Each battery cell 18 can have hundreds of electrode stacks 22. Each electrode stack 22 is connected to current collectors 24, 26. In addition, the electrode stack 22 is placed in a housing and the housing is filled with a suitable electrolyte. For example, the electrolyte is a liquid solution of an organic solvent and a lithium salt. The current collectors 24, 26 are thin metal plates or foils disposed on either side of the electrode stack 22, typically having a thickness between 0.4 mm and 1 mm. The current collectors can be made of, for example, copper or aluminum. The current collectors 24, 26 are attached to the electrode stack 22 to transmit current to an external circuit.

[0052] Additional references Figure 2B ,like Figure 2A , a partial cross-sectional view of a battery cell 18 is shown showing the layers in a single electrode stack 22 according to the present disclosure. Each electrode stack 22 is composed of a negative electrode or anode electrode 40 (foil) extending from a first side of the electrode stack 22, a separator 42, and a positive electrode or cathode electrode 44 (foil) extending from a second side of the electrode stack 22. The anode electrode 40 is typically a thin metal sheet or foil that includes an anode electrode tab 46 (e.g., a metal sheet) for providing electrical connection between the anode electrode and the current collector 24. Figure 2A Similarly, cathode electrode 44 is a thin metal plate or foil that includes cathode electrode tab 48 (as shown) for providing electrical connection between cathode electrode 44 and current collector 26. Figure 2A ). Multiple cathode electrode sheets form a foil stack.

[0053] The anode electrode 40 and the anode electrode sheet 46 are made of, for example, copper or other suitable materials, and are typically coated with graphite or graphite / silicon or other carbon-based materials or silicon oxide or lithiated silicon. The cathode electrode 44 and the cathode electrode sheet 48 are made of, for example, aluminum or other suitable materials, and are typically coated with a metal oxide, such as lithium cobalt oxide (LCO) or nickel cobalt aluminum (NCA) or lithium iron / manganese phosphate (LFP / LFMP) or lithium-rich manganese (LMR). The different metals of the battery cell 18 (copper anode and aluminum cathode) produce a galvanic reaction in the battery cell 18. The anode electrode 40, for example, copper, and the cathode electrode 44, for example, aluminum, have different standard reduction potentials and are separated from each other by a separator 42. The aluminum, which has a lower potential, will oxidize and release electrons, while the copper, which has a higher potential, will reduce and accept electrons. This process of releasing and accepting electrons will generate an electric current that can be used to power the device. Multiple anode electrode sheets form a foil stack.

[0054] The separator 42 is typically a thin porous film or material layer located between the anode electrode 40 and the cathode electrode 44, preventing the anode electrode 40 and the cathode electrode 44 from contacting and causing a short circuit. The separator 42 allows lithium ions to pass through and complete the circuit. Porous and chemically stable composite materials, such as those made from polyethylene (PE), polypropylene (PP), or other natural materials, can be used as the separator 42. Inorganic nanoparticles such as TiO2, SiO2, Al2O3, and ZrO2 can also be used to form a coating composite for the separator 42. The separator 42 increases the internal resistance of the battery cell 18, which reduces the power output and efficiency of the battery. The internal resistance depends on the thickness, porosity, and composition of the separator 42. The separator 42 is also selected to withstand high temperatures and manage thermal runaway, thereby preventing uncontrolled temperature increases caused by exothermic reactions. In addition, the separator 42 has a high melting point and low shrinkage to prevent contact between the anode electrode 40 and the cathode electrode 44. The separator 42 has sufficient mechanical strength to resist puncture, tearing, or deformation during the manufacture and operation of the battery assembly. The separator 42 is also dimensionally stable and flexible to conform to the shape of the electrode and accommodate volume changes during cycling. The separator 42 is chemically inert and compatible with the electrolyte, electrodes, and other battery components. In addition, the separator 42 has a low affinity for water or other impurities that could contaminate the electrolyte or cause electrode corrosion.

[0055] refer to Figure 3 , shows a method 100 for consolidating a foil stack of an electrode stack 22 within a battery cell 18 according to the present disclosure.

[0056] The method begins at box 102. Box 102 depicts combining the foils 46, 48 of the electrode stack 22 in the battery cell 18 to form a combined foil stack 52. The combined foils 46, 48 may include pre-assembling the electrode stack 22 in an upstream stacking process. For example, the anode electrode 40, the cathode electrode 44, and the separator may be deposited in a magazine (not shown) in a stacking wheel (not shown) and arranged separately to form the electrode stack 22. In this arrangement, the anode electrode sheet 46 extends from a first side of the electrode stack 22 and forms a combined foil stack 52 including the anode electrode sheet 46. The cathode electrode sheet 48 extends from the other side of the first side of the electrode stack 22 or another portion of the first side of the electrode stack 22 (i.e., away from the anode electrode sheet 46) and forms a combined foil stack 52 including the cathode electrode sheet 48. The combined foil stack 52 may include either the anode electrode sheet 46 or the cathode electrode sheet 48. In one example, while the combined foil stack 52 includes a stack of 50 electrode sheets, the number of electrode sheets may vary (eg, from fewer than 25 electrode sheets to more than 100 electrode sheets). The method may then move to block 104 .

[0057] Block 104 depicts clamping the combined foil stack 52 in place using the clamp 54 or the sub-clamp 56. Clamping the combined foil stack 52 may include using only the clamp 54 or using both the clamp 54 and the sub-clamp 56. As used herein and as Figure 4 As shown, the clamp 54 is used to hold and support the electrode stack 22, and the sub-clamp 56 is used to hold and support the combined foil stack 52 in preparation for hot pressing, but it should be understood that other configurations of the clamp 54 and the sub-clamp 56 may be used. Clamping can provide joining force for additional combinations of the combined foil stack 52. Due to the low inherent stiffness of the electrode sheets in the combined foil stack 52 and the residual stresses caused by the rolling and winding processes during the production and combination of the anode electrode sheet 46 and the cathode electrode sheet 48, uniform clamping of the combined foil stack 52 is advantageous. When the sub-clamp 56 is used, the sub-clamp 56 may contact only a portion of the combined foil stack 52 (e.g., a portion not used for hot pressing). In some cases, clamping the combined foil stack 52 may occur during a pre-assembly step and / or during an upstream stacking process. In addition, the clamp 54 and / or the sub-clamp 56 may be integrated with the die 60. Additionally, the fixture 54 and / or sub-fixtures 56 can be heated using, for example, induction heating (e.g., an induction heated fixture and / or induction heated sub-fixtures) and / or resistance heating (e.g., a resistance heated fixture and / or resistance heated sub-fixtures). The die 60, which incorporates an induction coil in a non-conductive tool, can compress the combined foil stack 52, and the induction coil heats the foil to form a diffusion bond. The method then moves to block 106.

[0058] Block 106 depicts hot pressing the combined foil stack 52 using the heated press die 60 to form the consolidated foil stack 62. Hot pressing the combined foil stack 52 heats the combined foil stack 52 and presses the individual electrode sheets together. The hot pressing step evaporates surface contamination and moisture on the individual electrode sheets while minimizing air cavities within the consolidated foil stack 62. Hot pressing reduces porosity and shedding within the consolidated foil stack 62 during the subsequent welding step.

[0059] Figure 5 、 8 , 10, 14-16 and 21 show a set of heated dies 60 for hot pressing the combined foil stack 52 to produce a consolidated foil stack 62, such as Figure 6 and Figure 9 6. The consolidated foil stack 62 shown in FIG. The die 60 may include a resistance heating die 60, an induction heating die 60, or the like. In a specific embodiment, prior to the hot pressing step, a combined foil stack 52 comprising 50 sheets having an initial total thickness of 890 microns (μm) is hot pressed to produce a consolidated foil stack 62 having a final total thickness of approximately 812 μm. In this example, the difference in thickness is due to the hot pressing step and the elimination of surface contamination and air cavities initially present between the foils 46 and 48. In another embodiment, hot pressing the combined foil stack 52 may include heating the combined foil stack 52 to a temperature between 350 Kelvin (K) and 680 K and maintaining the temperature for a period of ten seconds to thirty minutes. It should be understood that a variety of temperatures and holding times may be used for hot pressing. For example, the hot pressing temperature may be from 300 K or less to 900 K or greater, as long as the melting temperature of the combined foil stack 52 is not reached. The hot pressing time may be from less than 5 seconds to more than 30 minutes.

[0060] refer to Figures 10 to 13 Hot pressing the combined foil stack 52 may include forming at least one feature in the combined foil stack 52 . Figure 10 Hot pressing of the combined foil stack 52 using a heated die configured to emboss and / or form these features is shown. Figure 11 , shows a consolidated foil stack 62 having a plurality of indentation features 64 formed therein. The indentation features 64 can extend into and / or from the resulting consolidated foil stack 62. The consolidated foil stack 62 can have one or more indentation features 64. Figure 12 A consolidated foil stack 62 is shown having undulating features 66 formed therein. The undulating features 66 may be formed on an outer surface and / or throughout the consolidated foil stack 62. The undulating features 66 may facilitate improved gas ventilation during subsequent welding process steps. Figure 13A consolidated foil stack 62 is shown having a plurality of rib features 68 formed therein. The rib features 68 can extend into and / or from the consolidated foil stack 62. The consolidated foil stack 62 can have one or more rib features 68. These features can be used to enhance foil consolidation, particularly during transfer of the electrode stack 22 to a subsequent processing location.

[0061] Additionally, hot pressing the combined foil stack 52 may include trimming the combined foil stack 52 to allow for a consistent clamping fit. Figure 14 As shown, the heated die 60 may include a trimming feature 70 that trims and removes a portion 72 of the combined foil stack 52 such that an end 74 of the resulting consolidated foil stack 62 is, as shown, Figure 15 The method 100 may then move to block 108 .

[0062] Block 108 depicts cooling at least a portion of the sub-fixture 56 using the cooling system 76. For example and with reference to Figure 16 The sub-jig 56 having the cooling channels 78 may be used for the hot pressing step shown in block 106. The cooling channels 78 are embedded in and integral with the sub-jig 56 and deliver coolant throughout at least a portion of the sub-jig 56. When the heated die 60 heats and presses the combined foil stack 52, the sub-jig 56 cools the combined foil stack 52 and / or a portion of the electrode stack 22 to prevent the combined foil stack 52 from overheating.

[0063] In another embodiment, and with reference to Figure 17 , cooling at least a portion of the sub-clamp 56 may include using a sub-clamp 56 that includes a Peltier plate 80. The Peltier plate operates using the Peltier effect, which occurs when an electric current flows through the junction of two different materials. As a result, heat is transferred from one side of the plate (e.g., the cold side 82) to the other side of the plate (e.g., the hot side 84). Depending on the direction of the current, the Peltier plate can absorb heat (get cooler) or dissipate heat (get hotter). The Peltier plate 80 can be integrally provided with the sub-clamp 56 or can be separated from the sub-clamp 56 and / or the clamp 54. The Peltier plate 80 can be arranged so that the hot side is adjacent to and close to the combined foil stack 52, while the cold side is away from the combined foil stack 52 and away from the combined foil stack 52. The method then moves to box 110.

[0064] Block 110 depicts laser welding the consolidated foil stack 62 to the terminal lead 86 (e.g., current collector) using the laser welder 88. The laser welder 88 may include a high-frequency oscillation laser welder. It should be understood that the laser welder 88 may include various suitable welders. In an embodiment, laser welding the consolidated foil stack 62 may include, after the hot pressing step, using the laser welder 88 to weld the consolidated foil stack 62 to the terminal lead 86 in a vertical figure-eight oscillation pattern using high-beam oscillation.

[0065] Additionally, the consolidated foil stack 62 may be welded to the terminal leads 86 in various configurations. For example, Figure 18 As shown, the consolidated foil stack 62 may be welded to the terminal lead 86 in a butt configuration using a laser welder 88 , with the resulting weld 90 disposed at ends 92 of the consolidated foil stack 62 and the terminal lead 86 .

[0066] In such Figure 19 In the illustrated embodiment, the consolidated foil stack 62 is welded in an overlapping configuration, wherein the resulting weld 90 is disposed on a portion of the consolidated foil stack 62 where the consolidated foil stack 62 overlaps a portion of the terminal lead 86 .

[0067] In such Figure 20 In the illustrated embodiment, the consolidated foil stack 62 is welded in an overlapping configuration, wherein the resulting weld 90 is a fillet weld disposed on a portion of the consolidated foil stack 62 that overlaps a portion of the terminal lead 86 .

[0068] refer to Figure 21 , the heated die 60A may be used to heat a first consolidated foil stack 62A located on a first side 98A of the electrode stack 22. The cooled die 60B may be used to cool a second consolidated foil stack 62B located on a second side 98B of the electrode stack 22. The heating of the first consolidated foil stack 62A and the cooling of the second consolidated foil stack 62B may occur simultaneously (e.g., during the welding step depicted in block 110), or may occur separately.

[0069] The present invention offers advantages and benefits over prior art laser welding of electrode stacks. For example, hot pressing the combined foil stack 52 heats the foils 46 and 48, vaporizing surface contamination, typically in the form of aluminum oxide, and eliminating air cavities. During the subsequent welding step, due to the rapid solidification rate of the aluminum alloy, gases are trapped in the resulting weld, leading to the formation of pores. These pores, combined with the tension caused by solidification shrinkage, cause the foil to detach at the fusion boundary. Using hot pressing reduces porosity and detachment during subsequent welding.

[0070] The foregoing description is merely illustrative in nature and is not intended to limit the present disclosure, its application, or use. The broad teachings of the present disclosure can be implemented in many forms. Therefore, while this disclosure includes specific embodiments, the true scope of the disclosure should not be so limited, as other modifications will become apparent upon a study of the drawings, the specification, and the appended claims.

Claims

1. A method for consolidating a foil stack, comprising: combining foils of electrode stacks in a battery cell to form a combined foil stack; hot pressing the combined foil stack using a heated press die to form a consolidated foil stack; as well as The consolidated foil stack is laser welded to the terminal leads using a laser welder. 2 . The method of claim 1 , wherein the foil is formed of at least one of copper or aluminum. 3 . The method of claim 1 , wherein hot pressing the combined foil stack comprises heating the combined foil stack to a temperature between 350 Kelvin and 680 Kelvin and maintaining the temperature for 5 seconds to 30 minutes. The method of claim 1 , wherein hot pressing the combined foil stack comprises using an induction heated die. The method of claim 1 , wherein hot pressing the combined foil stack comprises using a resistively heated die. 6 . The method of claim 1 , wherein hot pressing the combined foil stack comprises forming at least one indentation feature in the combined foil stack using the heated die. 7 . The method of claim 1 , wherein hot pressing the combined foil stack comprises forming at least one wavy feature in the combined foil stack using the heated die. 8 . The method of claim 1 , wherein hot pressing the combined foil stack comprises forming at least one rib feature in the combined foil stack using the heated die.

9. The method of claim 1, wherein laser welding the combined foil stack comprises using a high frequency oscillating laser.

10. The method according to claim 1, further comprising: At least one of a portion of a jig or a portion of a sub-jig configured to hold the electrode stack during hot pressing of the combined foil stack is cooled.

Images