Welding stack of external tabs to terminal using two-step laser process that reduces defects

Abstract

A method for joining an external tab of a battery cell to a terminal includes providing a battery cell stack including C cathode electrodes, A anode electrodes, and S separators, where C, S, and A are integers greater than one. The method includes: arranging a stack of external tabs of one of the C cathode electrodes and the A anode electrodes on a terminal; during the first laser processing step, creating a trench in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at a welding location; and during a second laser treatment step, welding the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at the welding location.

Description

Technical Field

[0001] The information provided in this section is for the purpose of generally presenting the context of the present disclosure. To the extent described in this section, the work of the presently named inventors and aspects of the description that may not constitute prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0002] The present disclosure relates to battery cells, and more particularly to laser welding a stack of external tabs of electrodes to terminals of the battery cell. Background Art

[0003] An electric vehicle (EV), such as a battery electric vehicle (BEV), a hybrid vehicle, and / or a fuel cell vehicle, includes one or more motors and a battery system, which includes one or more battery cells, modules, and / or battery packs. A power control system is used to control the charging and / or discharging of the battery system during charging and / or driving. Summary of the invention

[0004] A method for joining an external tab of a battery cell to a terminal comprises: providing a battery cell stack, the battery cell stack comprising C cathode electrodes, A anode electrodes, and S separators, each cathode electrode comprising a cathode current collector made of foil, a cathode active layer arranged on the cathode current collector, and an external tab extending from the cathode current collector, the anode electrode comprising an anode current collector made of foil, an anode active layer arranged on the anode current collector, and an external tab extending from the anode current collector, wherein C, S, and A are integers greater than one. The method comprises: arranging a stack of external tabs of one of the C cathode electrodes and the A anode electrodes on the terminal; creating grooves in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at a welding location during a first laser processing step; and welding the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at the welding location during a second laser processing step.

[0005] In other features, both the first laser processing step and the second laser processing step are performed using a first laser. The method includes: after performing the first laser processing step, adjusting at least one of the laser power, laser scanning speed, laser focus / defocus, laser oscillation mode, workpiece speed, pulse frequency and / or pulse shape of the first laser for the second laser processing step. The first laser processing step and the second laser processing step are performed using the first laser and the second laser, respectively. The first laser is operated using laser operating parameters different from those of the second laser. At least one of the laser power, laser scanning speed, laser focus / defocus, workpiece speed, laser oscillation mode, pulse frequency and / or pulse shape of the second laser is different from that of the first laser.

[0006] In other features, the first laser is operated at a first focus setting and a first scanning speed, and the second laser is operated at a second focus setting and a second scanning speed. The first focus setting is less focused than the second focus setting, and the first scanning speed is higher than the second scanning speed. At least some defects generated during the first laser processing step are repaired during the second laser processing step.

[0007] In other features, the first laser comprises a cutting laser and the second laser comprises a welding laser. The first laser comprises a welding laser and the second laser comprises a welding laser. The method includes: disposing a fill material in the groove after the first laser processing step and before the second laser processing step.

[0008] A method for joining an external tab of a battery cell to a terminal comprises: providing a battery cell stack, the battery cell stack comprising C cathode electrodes, A anode electrodes, and S separators, each cathode electrode comprising a cathode current collector made of foil, a cathode active layer arranged on the cathode current collector, and an external tab extending from the cathode current collector, the anode electrode comprising an anode current collector made of foil, an anode active layer arranged on the anode current collector, and an external tab extending from the anode current collector, wherein C, S, and A are integers greater than one. The method comprises: arranging a stack of external tabs of one of the C cathode electrodes and the A anode electrodes on the terminal; during a first laser processing step, using a first laser to create a groove in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at a welding position; and during a second laser processing step, using a second laser to weld the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at the welding position.

[0009] In other features, the first laser and the second laser are operated using at least one different laser operating parameter selected from the group consisting of laser power, laser scanning speed, laser focus / defocus, workpiece speed, pulse frequency, and pulse shape.

[0010] In other features, the first laser comprises a cutting laser and the second laser comprises a welding laser. The first laser comprises a welding laser and the second laser comprises a welding laser. The first laser operates at a first focus setting and a first scanning speed, and the second laser operates at a second focus setting and a second scanning speed.

[0011] In other features, the first focus setting is less focused than the second focus setting. The first scanning speed is higher than the second scanning speed. At least some defects created by the first laser during the first laser processing step are repaired by the second laser during the second laser processing step.

[0012] The present invention may also include the following aspects.

[0013] 1. A method for joining an external tab of a battery cell to a terminal, comprising:

[0014] A battery cell stack is provided, the battery cell stack comprising:

[0015] C cathode electrodes, each cathode electrode comprising a cathode current collector made of foil, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0016] A anode electrode, the anode electrode comprising an anode current collector made of foil, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and

[0017] S baffles, where C, S, and A are integers greater than one; and

[0018] disposing a stack of external tabs of the C cathode electrodes and one of the A anode electrodes on a terminal;

[0019] During a first laser processing step, grooves are created in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at welding locations; and

[0020] During a second laser processing step, the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes is welded at the welding location.

[0021] 2. The method according to claim 1, wherein both the first laser processing step and the second laser processing step are performed using a first laser.

[0022] 3. The method according to Option 2 also includes: after performing the first laser processing step, adjusting at least one of the laser power, laser scanning speed, laser focus / defocus, laser oscillation mode, workpiece speed, pulse frequency and / or pulse shape of the first laser for use in the second laser processing step.

[0023] 4. The method according to claim 1, wherein the first laser processing step and the second laser processing step are performed using a first laser and a second laser, respectively.

[0024] 5. The method of claim 4, wherein the first laser is operated using different laser operating parameters than the second laser.

[0025] 6. The method according to claim 5, wherein at least one of the laser power, laser scanning speed, laser focus / defocus, workpiece speed, laser oscillation mode, pulse frequency and / or pulse shape of the second laser is different from that of the first laser.

[0026] 7. The method of claim 4, wherein the first laser operates at a first focus setting and a first scanning speed, and the second laser operates at a second focus setting and a second scanning speed.

[0027] 8. The method according to claim 7, wherein:

[0028] The first focus setting is less focused than the second focus setting; and

[0029] The first scanning speed is higher than the second scanning speed.

[0030] 9. The method of claim 1, wherein at least some defects created during the first laser processing step are repaired during the second laser processing step.

[0031] 10. The method of claim 4, wherein the first laser comprises a cutting laser and the second laser comprises a welding laser.

[0032] 11. The method of claim 4, wherein the first laser comprises a welding laser and the second laser comprises a welding laser.

[0033] 12. The method according to claim 1 further comprises: disposing a filling material in the trench after the first laser processing step and before the second laser processing step.

[0034] 13. A method for joining an external tab of a battery cell to a terminal, comprising:

[0035] A battery cell stack is provided, the battery cell stack comprising:

[0036] C cathode electrodes, each cathode electrode comprising a cathode current collector made of foil, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0037] A anode electrode, the anode electrode comprising an anode current collector made of foil, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and

[0038] S baffles, where C, S, and A are integers greater than one; and

[0039] disposing a stack of external tabs of the C cathode electrodes and one of the A anode electrodes on a terminal;

[0040] During a first laser processing step, using a first laser, creating a groove in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at a welding location; and

[0041] During a second laser processing step, the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes is welded at the welding location using a second laser.

[0042] 14. The method of claim 13, wherein the first laser and the second laser are operated using at least one different laser operating parameter.

[0043] 15. The method of claim 14, wherein the at least one different laser operating parameter is selected from the group consisting of laser power, laser scanning speed, laser focus / defocus, workpiece speed, pulse frequency, and pulse shape.

[0044] 16. The method of claim 13, wherein the first laser comprises a cutting laser and the second laser comprises a welding laser.

[0045] 17. The method of claim 16, wherein the first laser comprises a welding laser and the second laser comprises a welding laser.

[0046] 18. The method of claim 13, wherein the first laser operates at a first focus setting and a first scanning speed, and the second laser operates at a second focus setting and a second scanning speed.

[0047] 19. The method according to claim 18, wherein:

[0048] The first focus setting is less focused than the second focus setting; and

[0049] The first scanning speed is higher than the second scanning speed.

[0050] 20. The method of claim 13, wherein at least some defects created by the first laser during the first laser processing step are repaired by the second laser during the second laser processing step.

[0051] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the accompanying drawings.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. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present disclosure will become more fully understood from the detailed description and accompanying drawings, in which:

[0053] Figure 1A is a side cross-sectional view of an example of a battery cell including a cathode electrode, an anode electrode, and a separator according to the present disclosure;

[0054] Figure 1B is a side view of an example of a pouch-shaped battery cell according to the present disclosure;

[0055] Figure 1C is a perspective view of an example of a prismatic battery cell according to the present disclosure;

[0056] Figure 1D is a side cross-sectional view of an example of internal and external terminals of a prismatic battery cell according to the present disclosure;

[0057] Figure 2 is a side view of an example of an external tab of an electrode disposed on a terminal of a battery cell according to the present disclosure;

[0058] Figure 3 is a side view showing an example of a first laser processing step for laser welding an external tab stack of an electrode to a terminal of a battery cell according to the present disclosure;

[0059] Figure 4 is a side view showing an example of a defect in a groove at a welding location after a first laser processing step according to the present disclosure;

[0060] Figure 5 is a side view showing an example of a second laser processing step for laser welding an external tab stack of an electrode to a terminal of a battery cell according to the present disclosure;

[0061] Figure 6 is a side view of an example of an external tab stack and terminals after a second laser processing step according to the present disclosure;

[0062] Figure 7 is a side view of another example of laser welding an external tab stack to a terminal of a battery cell according to the present disclosure;

[0063] Figure 8 is a side view showing another example of a first laser processing step for laser welding an external tab stack to a terminal of a battery cell according to the present disclosure;

[0064] Fig. 9 is a side view showing another example of a defect in a groove at a welding location after a first laser processing step according to the present disclosure; and

[0065] Fig.10 is a side view illustrating another example of a second laser processing step for laser welding an external tab stack to an internal terminal of a battery cell according to the present disclosure.

[0066] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0067] Although the battery cells including laser welded internal terminals are shown in the context of an electric vehicle, the battery cells including laser welded internal terminals may be used in stationary applications and / or other applications.

[0068] The present disclosure addresses the quality of welding between external tabs extending from the current collectors of the anode and / or cathode electrodes and the terminals of the battery cell. In some examples, the terminals are internal terminals of the battery cell that contact the external terminals of the battery cell in the prismatic battery cell. In other words, the external terminals contact the internal terminals of the external tabs laser welded to the cathode electrode and / or the anode electrode. It is understood that separate terminals are used to connect the cathode and anode electrodes to external devices.

[0069] When welding multiple layers of external tabs (e.g., external tabs extending from a current collector made of foil) in a lap joint, the weld can be porous and detachment can occur at the fusion boundary. When laser welding is used, defects may occur. The present disclosure relates to joining external tabs of current collectors of anode and / or cathode electrodes to terminals using a two-step laser process to reduce or eliminate defects and improve weld quality. In some examples, laser welding is performed without ultrasonic welding.

[0070] Reference now Figure 1AThe battery cell 10 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a predetermined order in a stack 12, the stack being arranged in a housing 50, and the cathode electrodes 20-1, 20-2, ..., and 20-C (where C is an integer greater than one) include a cathode active layer 24 arranged on one side or both sides of a cathode current collector 26. A anode electrodes 40-1, 40-2, ..., and 40-A (where A is an integer greater than one) include an anode active layer 42 arranged on one side or both sides of an anode current collector 46.

[0071] The connections to the C cathode electrodes 20 and the A anode electrodes 40 are typically made into terminals. The C cathode electrodes 20 and the A anode electrodes 40 include external tabs 28 and 48, respectively, which correspond to the portions of the current collectors of the C cathode electrodes 20 and the A anode electrodes 40 that extend beyond the cathode and anode active material layers 24 and 42. In some examples, the external tabs 28 of the C cathode electrodes 20 are connected to internal terminals and the external tabs 48 of the A anode electrodes 40 are connected to another internal terminal. The internal terminals are connected to the external terminals of the battery cell. Although the lengths of the external tabs 28 and 48 are Figure 1A 48 are shown as being relatively short, but the external tabs 28 and 48 can extend to any distance required for welding or other purposes. The external tabs 28 and 48 can include a single external tab for each electrode or multiple external tabs for each electrode to provide redundant connections. The external tabs 28 and 48 can extend the width of the current collector or only extend a portion of the width of the current collector.

[0072] In some examples, cathode current collector 26 and anode current collector 46 include foil layers. In some examples, the current collector is made of one or more materials selected from the group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and alloys thereof. In some examples, anode active layer 42 and / or cathode active layer 24 include a coating comprising one or more active materials, one or more conductive fillers / additives, and / or one or more binder materials. In some examples, the battery cell and / or electrode is manufactured by applying a slurry to coat the current collector in a roll-to-roll manufacturing process.

[0073] Reference now Figure 1B , the pouch-shaped battery cell 52 includes a pouch-shaped housing 53, which includes a stack 56. As will be further described below, external tabs 57 of the anode and cathode electrodes are laser welded to terminals 54 and 55 extending through the pouch-shaped housing 53, respectively.

[0074] Reference now Figure 1C, the prismatic battery cell 58 includes a housing 60. Although a prismatic battery cell is shown for illustrative purposes, the two-step laser processing according to the present disclosure can be used to laser weld external tabs to terminals of cylindrical, pouch or other battery cell form factors. In some examples, the housing 60 has a rectangular cross-section in the x-axis plane, the y-axis plane, and the z-axis plane. The prismatic battery cell 58 includes external terminals 62 and 64 and a vent cover 66. A stack 12 of C cathode electrodes 20, A anode electrodes 40, and S separators 32 is arranged in the housing 60. As will be further described below, the external tabs of the anode collector and / or cathode collector are laser welded to the corresponding terminals. The terminals are arranged to contact the external terminals 62 and 64 of the battery cell 10 to provide external connections to the anode electrode and the cathode electrode.

[0075] Reference now Figure 1D , an example of internal terminals 84 and 86 of a prismatic battery cell is shown in the housing 60. The stack 12 of A anode electrodes or C cathode electrodes includes an external tab 88. The external tabs 88 of the A anode electrodes and / or C cathode electrodes are laser welded to the internal terminals 84 and 86, respectively, as will be further described below. Although the internal terminals 84 and 86 are shown as "L" shaped terminals, flat terminals or terminals having other shapes may also be used.

[0076] Reference now Figures 2 to 4 , shows an example of the first step of a two-step laser processing method. As can be appreciated, the two-step laser processing method can be used to join the external tabs of the anode or cathode electrode to the terminal (e.g., in a prismatic battery cell or other type of battery cell). Figure 2 In the embodiment of the present invention, a stack of external tabs 110 extending from a current collector of a cathode electrode or an anode electrode is arranged on a terminal 114 of the battery cell.

[0077] exist Figure 3 1 , a laser 120-1 is directed onto the welding location 118 to create a groove 119 in the stack of external tabs 110. The laser 120-1 cuts and / or melts the stack of external tabs 110. In some examples, material may be removed at the welding location 118 of the stack of external tabs 110 to form the groove 119. In some examples, the laser 120-1 may also penetrate and / or remove a portion of the internal terminal 114 located below the welding location 118, as shown at 121. In some examples, a vacuum source 124 including a vacuum tube 126 may be used to remove melted foil, debris, or other material from the groove 119 formed at the welding location 118 during the first laser processing step to clean the welding location 118 prior to the second laser processing step.

[0078] exist Figure 4, a stack of external tabs 110 is shown after a first laser processing step. During the first laser processing step, defects 130, such as voids or cracks, may be formed on the inner or outer surface of the stack of external tabs 110 within and / or near the grooves 119 formed at the welding locations 118. The defects are repaired during a second laser processing step.

[0079] Reference now Figure 5 and 6 , shows a second laser processing step for welding a stack of external tabs 110 of an anode or cathode electrode to an internal terminal of a battery cell. Laser 120-2 reheats weld location 118, the material melts, and defect 130 is removed. Laser 120-2 heats a slightly wider area than laser 120-1 and penetrates part or all of the thickness of terminal 114.

[0080] Prior to commencing the second laser processing step, the groove 119 at the weld location 118 may be at least partially filled with a weld filler material 133 that is compatible with the material of the foil and / or internal terminal 114 being welded. The weld filler material 133 may be used to replace material lost during the first laser processing step. After the second laser processing step, the foil material, internal terminal, filler material, and / or terminal reflow, and a final weld 143 is produced that has few or no defects, such as Figure 6 shown.

[0081] In some examples, lasers 120-1 and 120-2 are the same laser. In some examples, lasers 120-1 and 120-2 are different. For example, both lasers 120-1 and 120-2 can be welding lasers operated with different operating parameters. In other examples, laser 120-1 is a cutting laser and laser 120-2 is a welding laser. Examples of laser operating parameters include laser power, laser scanning speed, laser oscillation mode, laser focus / defocus, workpiece speed, pulse frequency and / or pulse shape. Laser operating parameters are used to change the amount of heating that occurs at a given position. The laser oscillation mode of the laser (e.g., such as a figure 8, a zigzag mode or other mode) can be used to adjust the heating of the welding position.

[0082] It will be appreciated that the final weld is only slightly larger than the groove 119 created during the first laser processing step. Increasing the weld area during the second laser processing step remelts defects at the edge of the weld location 118 and generally does not create new defects.

[0083] Now refer to Figures 7 to 9 , shows the first laser processing step of another two-step laser processing method. Figure 7In FIG. 2 , the stack 210 is arranged on the internal terminals 214 of the battery cells. Figure 8 In FIG. 2 , laser 220 - 1 heats the material at welding location 218 . In some examples, laser 120 penetrates a portion of inner terminal 214 below welding location 218 . Fig. 9 In the embodiment shown in FIG. 2 , during the first laser processing step, a cavity is formed at the welding location 218 , and material may be removed and / or defects 230 may be formed in the welding location 218 .

[0084] Reference now Fig.10 , showing a second laser processing step for connecting the foil of the external tab to the internal terminal of the battery cell. In some examples, before the second laser processing step, the cavity at the welding location can be at least partially filled with a welding filler material that is compatible with the foil. The laser 120 heats the welding location 218, and the defect 230 is removed. After further heating, the final weld 243 is formed, as shown in FIG. Fig.10 shown.

[0085] In some examples, lasers 220-1 and 220-2 correspond to a single laser operating with the same or different operating parameters. In some examples, lasers 220-1 and 220-2 are different and both are welding lasers. Examples of laser operating parameters include laser power, laser scanning speed, laser oscillation mode, laser focus / defocus, workpiece speed, pulse frequency and / or pulse shape. In some examples, laser 220-1 used during the first laser processing step uses a defocused laser beam and laser scanning performed at a first speed. In some examples, laser 220-2 used during the second processing step uses a focused laser beam and laser scanning performed at a second speed slower than the first speed.

[0086] It will be appreciated that the resulting weld is only slightly larger than the groove 119 created during the first laser processing step. Increasing the weld area during the second laser processing step remelts defects and generally does not create new defects.

[0087] The foregoing description is essentially only illustrative, and is in no way intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because after studying the drawings, the specification and the appended claims, other modifications will become apparent. It should be understood that without changing the principles of the present disclosure, one or more steps in the method can be performed in different orders (or simultaneously). In addition, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in the features of any one of the other embodiments and / or combined with the features of any one of the other embodiments, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with each other remains within the scope of the present disclosure.

[0088] Various terms are used to describe the spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.), including "connected," "engaged," "coupled," "adjacent," "next to," "on top," "above," "below," and "disposed." Unless explicitly described as "directly," when the relationship between a first and a second element is described in the above disclosure, the relationship may be a direct relationship in which no other intervening elements exist between the first and second elements, but may also be an indirect relationship in which one or more intervening elements exist (spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be interpreted to mean a logic (A ORB OR C) using a non-exclusive logical OR, and should not be interpreted to mean "at least one of A, at least one of B, and at least one of C."

[0089] In the drawings, the direction of the arrows, as indicated by the arrows, generally represents the flow of information (e.g., data or instructions) of interest to the illustration. For example, when element A and element B exchange various information, but the information sent from element A to element B is relevant to the illustration, the arrow may be directed from element A to element B. The unidirectional arrow does not imply that no other information is sent from element B to element A. In addition, for information sent from element A to element B, element B may send a request for the information or a confirmation of receipt of the information to element A.

Claims

1. A method for joining an external tab of a battery cell to a terminal, comprising: A battery cell stack is provided, the battery cell stack comprising: C cathode electrodes, each cathode electrode comprising a cathode current collector made of foil, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector; A anode electrode, the anode electrode comprising an anode current collector made of foil, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and S baffles, where C, S, and A are integers greater than one; and disposing a stack of external tabs of the C cathode electrodes and one of the A anode electrodes on a terminal; During a first laser processing step, grooves are created in the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes at welding locations; and During a second laser processing step, the stack of the external tabs of the one of the C cathode electrodes and the A anode electrodes is welded at the welding location.

2. The method according to claim 1, wherein: Both the first laser processing step and the second laser processing step are performed using a first laser.

3. The method according to claim 2, further comprising: After performing the first laser processing step, at least one of the laser power, laser scanning speed, laser focus / defocus, laser oscillation mode, workpiece speed, pulse frequency and / or pulse shape of the first laser is adjusted for the second laser processing step.

4. The method according to claim 1, wherein: The first laser processing step and the second laser processing step are performed using a first laser and a second laser, respectively.

5. The method according to claim 4, wherein: The first laser is operated using different laser operating parameters than the second laser.

6. The method according to claim 5, wherein: At least one of laser power, laser scanning speed, laser focus / defocus, workpiece speed, laser oscillation mode, pulse frequency and / or pulse shape of the second laser is different from that of the first laser.

7. The method according to claim 4, wherein: The first laser is operated at a first focus setting and a first scanning speed, and the second laser is operated at a second focus setting and a second scanning speed.

8. The method according to claim 7, wherein: The first focus setting is less focused than the second focus setting; and The first scanning speed is higher than the second scanning speed.

9. The method according to claim 1, wherein: At least some of the defects created during the first laser processing step are repaired during the second laser processing step.

10. The method according to claim 4, wherein: The first laser comprises a cutting laser and the second laser comprises a welding laser.

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