Bonding external tab of electrode of battery cell to terminal using pulsed laser

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; w weld segments are laser welded in each of L weld locations on the stack of the external tabs of one of the C cathode electrodes and the A anode electrodes to join the external tabs of one of the C cathode electrodes and the A anode electrodes to the terminal, where W and L are integers greater than one.

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 joining external tabs of electrodes of a battery cell to terminals using a pulsed laser. 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, an anode electrode and S separators, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector, the anode electrode comprising an anode current collector, an anode active layer disposed 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 the C cathode electrodes and one of the A anode electrodes on the terminal; laser welding W welding segments in each of L welding positions on the stack of external tabs of the C cathode electrodes and one of the A anode electrodes to join the external tab of the C cathode electrodes and one of the A anode electrodes to the terminal, wherein W and L are integers greater than one.

[0005] In other features, for each of the L welding positions, the W welding segments are arranged parallel to each other in a first diagonal direction. For each of the L welding positions, the W welding segments include a first group arranged parallel to each other in the first diagonal direction and a second group arranged parallel to each other in a second diagonal direction and overlapping the first group. For each of the L welding positions, the W welding segments are arranged parallel to each other in a first direction parallel to an outer edge of the stack including the outer tab. For each of the L welding positions, the W welding segments are arranged parallel to each other in a first direction perpendicular to an outer edge of the stack including the outer tab.

[0006] In other features, for each of the L welding locations, the W welding segments include a first group and a second group, the first group being arranged parallel to each other in a first direction parallel to an outer edge of the stack including the outer tab, and the second group being arranged parallel to each other in a second direction perpendicular to an outer edge of the stack including the outer tab and overlapping the first group. The L welding locations are arranged in a row positioned parallel to and spaced apart from an outer edge of the stack including the outer tab. The L welding locations are arranged in a row positioned parallel to and overlapping an outer edge of the stack including the outer tab.

[0007] In other features, the W weld segments in each of the L weld locations are formed in a predetermined order without sequentially welding immediately adjacent ones of the W weld segments in each of the L weld locations. The L weld locations are formed on the stack of external tabs in a predetermined order without sequentially welding immediately adjacent ones of the L weld locations. The L weld locations are formed in a predetermined order including laser welding an outer one of the L weld locations before laser welding an inner one of the L weld locations.

[0008] In other features, the stack of external tabs is trimmed at an acute angle to form a sloped edge, and the L welding locations are arranged in a row along the sloped edge. At least one of the anode current collectors of the A anode electrodes and the cathode current collectors of the C cathode electrodes is made of foil.

[0009] A battery cell includes a terminal. The battery cell stack includes C cathode electrodes, an anode electrode, and S separators, each cathode electrode including a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector, and the anode electrode includes an anode current collector, an anode active layer disposed 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 stack of the external tabs of one of the C cathode electrodes and the A anode electrodes is laser welded to the terminal. The laser welding between the stack of the external tabs of one of the C cathode electrodes and the A anode electrodes and the terminal includes W welding segments in each of L welding positions, wherein W and L are integers greater than one.

[0010] In other features, for each of the L welding locations, the W welding segments are arranged parallel to each other in at least one of a first diagonal direction and a second diagonal direction. For each of the L welding locations, the W welding segments are arranged parallel to each other in a first direction that is parallel to and perpendicular to at least one of an outer edge of the stack of the external tabs of one of the C cathode electrodes and the A anode electrodes. The L welding locations are arranged in a row that is positioned parallel to and spaced apart from an outer edge of the stack of the external tabs. The L welding locations are arranged in a row that is positioned parallel to and overlaps an outer edge of the stack of the external tabs.

[0011] In other features, the stack of external tabs is trimmed at an acute angle to form a sloped edge, and the L welding locations are arranged in a row along the sloped edge. At least one of the anode current collectors of the A anode electrodes and the cathode current collectors of the C cathode electrodes is made of foil.

[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, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0017] A anode electrode, the anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external contact extending from the anode current collector.

[0018] films; and

[0019] S baffles, where C, S, and A are integers greater than one; and

[0020] disposing a stack of external tabs of the C cathode electrodes and one of the A anode electrodes on a terminal;

[0021] W welding segments are laser welded in each of L welding locations on the stack of the external tabs of the C cathode electrodes and one of the A anode electrodes to join the external tab of the C cathode electrodes and one of the A anode electrodes to the terminal, where W and L are integers greater than one.

[0022] 2. The method according to claim 1, wherein, for each of the L welding positions, the W welding segments are arranged parallel to each other in a first diagonal direction.

[0023] 3. The method according to claim 1, wherein, for each of the L welding positions, the W welding segments include a first group arranged parallel to each other in a first diagonal direction and a second group arranged parallel to each other in a second diagonal direction and overlapping the first group.

[0024] 4. The method according to claim 1, wherein, for each of the L welding locations, the W welding segments are arranged parallel to each other in a first direction parallel to an outer edge of the stack including the outer tab.

[0025] 5. The method according to claim 1, wherein, for each of the L welding locations, the W welding segments are arranged parallel to each other in a first direction perpendicular to an outer edge of the stack including the outer tab.

[0026] 6. A method according to Option 1, wherein, for each of the L welding positions, the W welding segments include a first group and a second group, the first group being arranged parallel to each other in a first direction parallel to an outer edge of the stack including the external tab, and the second group being arranged parallel to each other in a second direction perpendicular to an outer edge of the stack including the external tab and overlapping with the first group.

[0027] 7. The method of claim 1, wherein the L welding locations are arranged in a row positioned parallel to and spaced apart from an outer edge of the stack including the outer tab.

[0028] 8. The method of claim 1, wherein the L welding locations are arranged in a row positioned parallel to and overlapping an outer edge of the stack including the outer tab.

[0029] 9. The method according to claim 1, wherein the W welding segments in each of the L welding positions are formed in a predetermined order without sequentially welding immediately adjacent welding segments among the W welding segments in each of the L welding positions.

[0030] 10. The method according to claim 1, wherein the L welding positions are formed on the stack of the external tabs in a predetermined order without sequentially welding adjacent welding positions among the L welding positions.

[0031] 11. The method according to claim 10, wherein the L welding locations are formed in a predetermined order, including laser welding outer welding locations of the L welding locations before laser welding inner welding locations of the L welding locations.

[0032] 12. The method according to claim 1, wherein:

[0033] The stack of outer tabs is trimmed at an acute angle to form a beveled edge; and

[0034] L welding positions are arranged in a row along the inclined edge.

[0035] 13. The method according to claim 1, wherein at least one of the anode current collectors of the A anode electrodes and the cathode current collectors of the C cathode electrodes is made of foil.

[0036] 14. A battery cell comprising:

[0037] Terminals; and

[0038] A battery cell stack, the battery cell stack comprising:

[0039] C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0041] A anode electrode, the anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external contact extending from the anode current collector.

[0042] films; and

[0043] S baffles, where C, S and A are integers greater than one;

[0044] wherein the stack of the external tabs of one of the C cathode electrodes and the A anode electrodes is laser welded to the terminal, and

[0045] Wherein, the laser welding between the stack of the external tabs of one of the C cathode electrodes and the A anode electrodes and the terminal includes W welding segments in each of L welding locations, wherein W and L are integers greater than one.

[0046] 15. The battery cell according to claim 14, wherein, for each of the L welding positions, the W welding sections are arranged parallel to each other in at least one of a first diagonal direction and a second diagonal direction.

[0047] 16. A battery cell according to Option 14, wherein, for each of the L welding positions, the W welding segments are arranged parallel to each other in a first direction, and the first direction is parallel to and perpendicular to at least one of the outer edges of the stack of the external tabs including the C cathode electrodes and one of the A anode electrodes.

[0048] 17. The battery cell of claim 14, wherein the L welding locations are arranged in rows positioned parallel to and spaced apart from an outer edge of the stack including the external tabs.

[0049] 18. The battery cell of claim 14, wherein the L welding locations are arranged in a row positioned parallel to and overlapping an outer edge of the stack including the external tab.

[0050] 19. The battery cell according to claim 14, wherein:

[0051] The stack of outer tabs is trimmed at an acute angle to form a beveled edge; and

[0052] The L welding positions are arranged in a row along the inclined edge.

[0053] 20. The battery cell according to claim 14, wherein at least one of the anode current collectors of the A anode electrodes and the cathode current collectors of the C cathode electrodes is made of foil.

[0054] 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

[0055] The present disclosure will become more fully understood from the detailed description and accompanying drawings, in which:

[0056] 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;

[0057] Figure 1B is a side view of an example of a pouch-shaped battery cell according to the present disclosure;

[0058] Figure 1C is a perspective view of an example of a prismatic battery cell according to the present disclosure;

[0059] 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;

[0060] Figure 2is a perspective view showing an example of a method for joining a stack of external tabs of a cathode or anode electrode to a terminal according to the present disclosure;

[0061] Figure 3 An example of a welding sequence for producing a weld segment at a welding location according to the present disclosure is shown;

[0062] Figure 4 shows other examples of welding sequences for forming welding locations to join a stack of external tabs of a cathode or anode electrode to a terminal in accordance with the present disclosure;

[0063] Figures 5A to 5F is an example of a welding pattern of a welding segment at each welding location according to the present disclosure;

[0064] Figure 6 and 7 is a perspective view showing an example of a method for joining a stack of external tabs to a terminal according to the present disclosure; and

[0065] Figure 8 is a side cross-sectional view showing one of the welded sections of a stack of joined external tabs and a terminal 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 terminals are shown in the context of an electric vehicle, the battery cells including laser welded 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 current collectors of anode and / or cathode electrodes of a battery cell and terminals. In some examples, the terminals correspond to internal terminals of the battery cell that contact the external terminals of the battery cell. In other words, the external terminals contact the internal terminals of the external tabs laser welded to the cathode and / or anode electrodes.

[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. The present disclosure relates to a method for joining external tabs of electrodes of a battery cell at multiple welding locations. Each welding location includes a welding segment formed by a series of short laser pulses. The welding segments are generated in a predetermined welding sequence and arranged in a predetermined welding pattern. Using a predetermined welding sequence and / or pattern helps to manage the heat generated during welding and reduce the interaction time between the laser beam and the material. This method also reduces shrinkage and minimizes detachment in the weld area of ​​the lap joint. The energy, frequency, speed, and position of the pulsed laser beam are optimized to provide sufficient energy to penetrate the stack and terminal of the external tabs, thereby producing a strong weld while preventing detachment and / or reducing thermal deformation. In some examples, each of the welding segments 132 is shorter than the width, height, or diagonal length of the outer boundary of the welding location 130. In some examples, the outer boundary of the welding location 130 is rectangular, but other boundary shapes can be used.

[0070] Reference now Figure 1A , the 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 in a housing 50, where A, C, and S are integers greater than one. The C cathode electrodes 20-1, 20-2, ..., and 20-C (where C is an integer greater than one) include a cathode active material layer 24 disposed on one or both sides of a cathode current collector 26. The A anode electrodes 40-1, 40-2, ..., and 40-A (where A is an integer greater than one) include an anode active material layer 42 disposed on one or both sides of an anode current collector 46. In some examples, the S separators 32 are disposed between the C cathode electrodes 20 and the A anode electrodes 40.

[0071] 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 cathode current collector 26 and the anode current collector 46 that extend beyond the cathode active material layer 24 and the anode active material layer 42, respectively. In some examples, the external tabs 28 of the C cathode electrodes 20 are laser welded to the first terminal and the external tabs 48 of the A anode electrodes 40 are laser welded to the second terminal, as will be further described below. In some examples, the terminals are internal terminals connected to the external terminals of the battery cell. If required for laser welding or other purposes, Figure 1A The outer tabs 28 and 48 in the embodiment may extend a longer distance.

[0072] External tabs 28 and 48 may include a single external tab per current collector or multiple external tabs per current collector to provide redundant connections. External tabs 28 and 48 may extend the width of the current collector or extend only a portion of the width of the current collector.

[0073] In some examples, cathode current collector 26 and anode current collector 46 include foil layers. In some examples, cathode current collector 26 and anode current collector 46 are made of one or more materials selected from the group of copper, stainless steel, brass, bronze, zinc, aluminum and alloys thereof. In some examples, cathode active material layer 24 and / or anode active material layer 46 include a coating on one or both sides of cathode current collector 26 and anode current collector 46, respectively. The coating may include one or more active materials, one or more conductive fillers / additives and / or one or more binder materials. In some examples, the electrode is manufactured by applying a slurry to coat the current collector in a roll-to-roll manufacturing process.

[0074] 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.

[0075] Reference now Figure 1C , the battery cell can be a prismatic battery cell 58 including a housing 60. Although a prismatic battery cell is shown for illustrative purposes, other types of battery cells can be used. 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 28 and 48 of the cathode collector and / or the anode collector are laser welded to the corresponding terminals. In some examples, 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.

[0076] 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 optionally folded and 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.

[0077] Reference now Figure 2 , the stack 110 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 as described above. The stack 110 includes a stack of external tabs 112 extending from the current collector of the anode electrode or the cathode electrode. The stack of external tabs 112 is located near the active material area 114 of the anode electrode or the cathode electrode. The stack of external tabs 112 is arranged on a terminal 116, such as an internal or external terminal of the battery cell.

[0078] The laser 120 directs short laser pulses onto the stack of external tabs 112 of the anode or cathode electrodes to produce weld segments 132 of a plurality of weld locations 130-1, 130-2, ..., and 130-L (collectively or individually referred to as weld locations 130), where L is an integer greater than zero. In some examples, the weld locations 130 are aligned in a row on the stack of external tabs 112 across the width of the stack 110. Alternatively, the weld locations 130 may include an array of weld locations that includes more than one row. In further examples, the weld locations 130 may be arranged in other regular or irregular patterns.

[0079] Each welding location 130 includes a plurality of welding segments 132 arranged in a predetermined pattern. Figure 2 In FIG. 1 , the plurality of weld segments 132 includes P diagonally oriented laser pulse welds, where P is an integer (eg, P=5). The laser 120 heats and melts the weld segments 132 at the weld locations 130 and joins the stack of external tabs 112 to the terminals 116 .

[0080] In some examples, laser 120 or another laser (not shown) performs an initial transfer using different laser welding parameters or a different laser to preheat the weld segment and / or weld location before performing laser welding. Examples of laser operating parameters that can be changed for preheating and / or laser welding include laser power, laser scanning speed, laser oscillation mode, laser focus / defocus, workpiece speed, pulse frequency, and / or pulse shape. Using a different laser and / or changing laser operating parameters can be used to change the amount of heating that occurs in a given location during preheating compared to welding.

[0081] Reference now Figure 3, showing a welding sequence in one of the welding positions 130. In some examples, the welding segments 132 are welded in a non-sequential manner. For example, the welding position 130 includes welding segments 132-1, 132-2, 132-3, 132-4, and 132-5 arranged in the order of -1 to -5 from the lower left to the upper right of the welding position. In some examples, welding segments are generated non-sequentially according to the welding sequence of the present disclosure, so that two adjacent welding segments are not welded sequentially. This method reduces overheating, deformation, and / or shrinkage by dissipating heat in external tabs and terminals. For example, the non-sequential welding sequence creates welding segments for odd-numbered welding positions from the lower left to the upper right, and then creates welding segments for even-numbered positions from the lower left to the upper right.

[0082] Reference now Figure 4 , shows a sequence for laser welding the welding positions 130-1, 130-2, ... and 130-L, where L is an integer greater than 2. In this example, L=7, although L can be set equal to other integers. In some examples, adjacent welding positions in the welding positions 130 are welded in a non-sequential order. In the first welding sequence at 180, the welding segments 132 in the welding positions 130 are produced by alternating between the outermost welding positions, then alternating between the next innermost welding positions, and so on. In some examples, the welding segments in the welding positions 130 are performed in the following order: 130-1, 130-7, 130-2, 130-6, 130-3, 130-5, and 130-4.

[0083] In the second welding sequence at 190, the welding segments 132 in the welding positions 130 are performed from the outermost welding position on one side to the middle welding position, to the outermost welding position on the other side to the middle welding position, etc. In some examples, the welding segments in the welding positions 130 are performed in the following order: 130-1, 130-4, 130-7, 130-2, 130-5, 130-3, and 130-4. It will be appreciated that other laser welding sequences of welding positions and / or welding segments may be performed.

[0084] Reference now Figures 5A to 5F , showing different arrangements of welding segments 132 at welding locations 130. Figure 5A , the welding segment 132 in the welding location 130 extends diagonally and parallely from the left side of the welding location upward to the right side. In some examples, the welding segment extends diagonally at a predetermined angle in the range of 30° to 60° (e.g., 45°) relative to the outer edge 192 of the stack of external tabs 112. Figure 5B In FIG. 1 , the welding section 132 in the welding location 130 extends diagonally and parallely from the right side of the welding location upward to the left side. Figure 5C, the weld segments 132 in the weld locations 130 extend diagonally in two directions to form a cross-hatch pattern.

[0085] exist Figure 5D In FIG. 1 , the weld segments 132 in the weld locations 130 extend in a first direction (eg, perpendicular to the outer edge 192 of the stack of outer tabs 112) and are parallel to each other. Figure 5E In FIG. 1 , the weld segments 132 in the weld locations 130 extend in a second direction (eg, parallel to the outer edge 192 of the stack of outer tabs 112) and are parallel to each other. Fig. 5F , the weld segments 132 in the weld locations 130 extend in a first direction and a second direction (transverse to the first direction) to form a cross-hatch pattern.

[0086] The welding locations can be arranged within the outer edge of the outer tab stack, such as Figure 2 In other examples, the welding location can be arranged between the outer edge 192 of the stack of external tabs 112 and the edge of the active material layer 114, such as Figure 6 In other examples, the stack of external tabs 112 can be trimmed at an acute angle along the outer edge 192 of the stack of external tabs 112 to form a beveled edge 200. The welding location 130 is positioned along the beveled edge 200 of the stack of external tabs 112, such as Figure 7 shown.

[0087] Now refer to Figure 8 , shows a cross section at one of the weld segments 132. The weld penetration at the weld segment 132 extends partially or completely through the thickness of the terminal 116, thereby ensuring a secure weld.

[0088] 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.

[0089] 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."

[0090] 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, 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, 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; W welding segments are laser welded in each of L welding locations on the stack of the external tabs of the C cathode electrodes and one of the A anode electrodes to join the external tab of the C cathode electrodes and one of the A anode electrodes to the terminal, where W and L are integers greater than one.

2. The method according to claim 1, wherein: For each of the L welding positions, the W welding segments are arranged parallel to each other in a first diagonal direction.

3. The method according to claim 1, wherein: For each of the L welding positions, the W welding sections include a first group arranged parallel to each other in a first diagonal direction and a second group arranged parallel to each other in a second diagonal direction and overlapping the first group.

4. The method according to claim 1, wherein: For each of the L welding locations, the W welding segments are arranged parallel to each other in a first direction parallel to an outer edge of the stack including the outer tab.

5. The method according to claim 1, wherein: For each of the L welding locations, the W welding segments are arranged parallel to each other in a first direction perpendicular to an outer edge of the stack including the outer tab.

6. The method according to claim 1, wherein: For each of the L welding positions, the W welding segments include a first group and a second group, wherein the first group is arranged parallel to each other in a first direction parallel to the outer edge of the stack including the external tab, and the second group is arranged parallel to each other in a second direction perpendicular to the outer edge of the stack including the external tab and overlaps with the first group.

7. The method according to claim 1, wherein: The L welding locations are arranged in rows located parallel to and spaced apart from an outer edge of the stack including the outer tab.

8. The method according to claim 1, wherein: The L welding locations are arranged in a row located parallel to and overlapping an outer edge of the stack including the outer tab.

9. The method according to claim 1, wherein: The W welding sections in each of the L welding positions are formed in a predetermined order without sequentially welding immediately adjacent welding sections among the W welding sections in each of the L welding positions.

10. The method according to claim 1, wherein: The L welding positions are formed on the stack of the external tabs in a predetermined order without sequentially welding adjacent welding positions among the L welding positions.

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