Secondary battery manufacturing method and secondary battery

Abstract

To provide a method for manufacturing a secondary battery that is capable of manufacturing a secondary battery having high quality and highly durable welded portions.SOLUTION: In a weld portion formation step, one welding step is performed such that center lines M1, M2, M3 along a longitudinal direction of weld beads 41, 42, 43 formed in the one welding step are deviated in a width direction perpendicular to the longitudinal direction of the weld beads 41, 42, 43 formed in the other welding step relative to center lines M1, M2, M3 along the longitudinal direction of adjacent weld beads 41, 42, 43 formed in the other welding step, and such that the weld beads 41, 42, 43 formed in the one welding step have overlapping portions D1, D2, D3 at both ends in the longitudinal direction where they partially overlap the weld beads 41, 42, 43 formed in the other welding step, thereby forming a weld portion 40 consisting of multiple weld beads 41, 42, 43 arranged in a staggered pattern.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a secondary battery and a secondary battery. [Background technology]

[0002] Conventionally, secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries have been used as power sources for electric vehicles, hybrid vehicles, etc. In this type of secondary battery, an electrode body and the like are housed in a case having an opening, and a sealing plate is welded to the opening. As a method for welding a sealing plate to a case in such a secondary battery, a manufacturing method of a sealed battery disclosed in Patent Document 1 has been proposed.

[0003] In the method for manufacturing a sealed battery described in Patent Document 1, in order to weld a lid to a case body, a first step is performed in which a plurality of first weld beads are sequentially formed at intervals, and a second step is performed in which a second weld bead is formed in a gap portion located between the first weld beads. As a result, a weld portion is formed that connects an opening edge portion of the case body and an outer peripheral edge portion of the lid, and the lid is welded to the case body. In Patent Document 1, the weld portion is formed by connecting a plurality of first weld beads and second weld beads to each other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-59408 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing method of a sealed battery described in Patent Document 1, a first weld bead is formed, and then a second weld bead is formed to form a welded portion in which a plurality of first weld beads and second weld beads are connected to each other. Therefore, when forming the second weld bead, the already welded portions (both ends in the length direction of the first weld bead) are welded again, and there is a possibility that welding defects such as reheat cracking will occur in the rewelded portions (rewelded portions).

[0006] In particular, in the manufacturing method of a sealed battery described in Patent Document 1, a weld is formed in which the first weld bead and the second weld bead are aligned in a substantially straight line, and most of both ends of the first weld bead in the longitudinal direction are rewelded. Therefore, the rewelded areas are large and welding defects are likely to occur. Therefore, the manufacturing method of a sealed battery described in Patent Document 1 has a problem in that the quality and durability of the welds are likely to be reduced.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a method for manufacturing a secondary battery capable of manufacturing a secondary battery having a welded part that is high quality and highly durable, and a secondary battery having a welded part that is high quality and highly durable. [Means for solving the problem]

[0008] The characteristic configuration of the method for producing a secondary battery according to the present invention for achieving the above object is as follows: A method for manufacturing a secondary battery including a housing having an opening and housing an electrode assembly therein, and a lid that seals the opening of the housing, comprising the steps of: a welded portion forming step of performing a welding step of laser-welding an opening edge portion of the housing and an outer peripheral edge portion of the lid body to sequentially form a plurality of weld beads at intervals at least twice to form a welded portion; In the weld portion forming step, one welding step is performed such that a center line along the length direction of the weld bead formed in the one welding step is shifted in a width direction perpendicular to the length direction of the weld bead formed in the other welding step with respect to a center line along the length direction of an adjacent weld bead formed in the other welding step, and the weld bead formed in the one welding step has overlapping portions at both ends in the length direction where the weld bead formed in the other welding step partially overlaps with the weld bead formed in the other welding step, thereby forming the weld portion at least a portion of which is constituted by a plurality of the weld beads arranged in a staggered pattern; The amount of deviation between a center line along the length of the weld bead formed in one welding process and a center line along the length of the weld bead formed in another welding process is within a range of 10% to 40% of the overall width of the weld bead formed in the other welding process.

[0009] According to the above characteristic configuration, the overlapping portion of the weld beads is smaller than when the weld beads are arranged in a straight line. In other words, in the above manufacturing method, when the weld beads are formed by laser welding, the number of re-welded portions is reduced, and the occurrence of welding defects is suppressed. Therefore, according to the manufacturing method of the secondary battery having the above characteristic configuration, it is possible to manufacture a secondary battery with improved quality of the welds compared to when the weld beads are arranged in a straight line. In addition, according to the above-described characteristic configuration, the weld beads are arranged in a staggered pattern, and the weld length is increased, which reduces stress against external forces such as internal pressure and increases the durability of the welds in the secondary battery. Furthermore, according to the above characteristic configuration, since the welding process in which multiple weld beads are formed by multiple laser welding is performed multiple times to form the weld, the cooling of the weld is slower than in a method in which the weld is formed by a single laser welding, and weld cracks due to rapid cooling can be prevented. This increases the weld strength of the secondary battery. Furthermore, since the time required for one laser welding is shortened, the amount of heat transferred to components (peripheral components) such as the resin member and electrodes attached to the lid can be reduced. This prevents melting and thermal settling of the resin member due to heat generated during welding, and deterioration of the electrodes, and thus prevents the performance degradation of the secondary battery caused by these factors. In this manner, the method for manufacturing a secondary battery according to the present invention makes it possible to suitably manufacture a secondary battery having welds that are of high quality and have high durability.

[0010] The secondary battery according to the present invention, which achieves the above object, has the following characteristic configuration: A housing having an opening and housing an electrode body therein; a cover that seals the opening of the housing, a weld portion formed by laser welding an opening edge portion of the housing and an outer circumferential edge portion of the lid body, the weld portion being composed of a plurality of weld beads; at least some of the plurality of weld beads are arranged in a staggered pattern in which a center line along the length direction of one of the weld beads is shifted in a width direction perpendicular to the length direction of the other adjacent weld bead with respect to a center line along the length direction of the other adjacent weld bead, and one of the weld beads has overlapping portions at both ends in the length direction that partially overlap with the other adjacent weld bead, The amount of deviation between the center line along the length of one of the weld beads and the center line along the length of another of the adjacent weld beads is within a range of 10% to 40% of the total width of the other of the adjacent weld beads.

[0011] According to the above characteristic configuration, when the housing and the lid are laser-welded to each other, the overlapping portion of the weld beads is smaller and the number of re-welded portions is reduced, which reduces the occurrence of welding defects, compared to when multiple weld beads are arranged in a straight line. Therefore, the secondary battery having the above characteristic configuration has improved quality of the welds compared to when multiple weld beads are arranged in a straight line. In addition, according to the above-mentioned characteristic configuration, since the multiple weld beads are arranged in a staggered pattern and the weld length is increased, stress against external forces such as internal pressure is reduced. Therefore, the secondary battery having the above-mentioned characteristic configuration has high durability at the welded portion. Thus, the secondary battery according to the present invention has welds of high quality and high durability. Effect of the Invention

[0012] As described above, according to the manufacturing method of the secondary battery of the present invention, a secondary battery having a welded portion with high quality and high durability can be manufactured, and the secondary battery of the present invention has a welded portion with high quality and high durability. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view of a secondary battery including a sealing body according to an embodiment; [Diagram 2] FIG. 1 is a cross-sectional view showing a schematic configuration of a secondary battery. [Diagram 3] FIG. 2 is a top view showing a secondary battery. [Figure 4] FIG. 4 is an enlarged view of part A in FIG. [Diagram 5] FIG. 11 is a schematic diagram for explaining a state after a first welding step in the weld portion forming step. [Figure 6] FIG. 11 is a schematic diagram for explaining a second welding step in the weld portion forming step. [Figure 7] FIG. 11 is a schematic diagram for explaining a state after a second welding step in the welded portion forming step. [Figure 8] FIG. 8 is an enlarged view of part B in FIG. [Figure 9] FIG. 11 is a schematic diagram for explaining a third welding step in the weld portion forming step. [Figure 10] FIG. 11 is a top view showing a secondary battery according to another embodiment. [Figure 11] FIG. 11 is a top view showing a secondary battery according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a method for manufacturing a secondary battery and the secondary battery according to an embodiment of the present invention will be described with reference to the drawings. Note that, in the following, an embodiment in which the secondary battery is a lithium ion secondary battery will be described as an example. In addition, in the following, each description and each drawing will be appropriately simplified in order to clarify the description.

[0015] [Overview of secondary battery 1] Fig. 1 is a perspective view of a secondary battery 1 manufactured by the manufacturing method for a secondary battery according to this embodiment. Fig. 2 is a cross-sectional view showing a schematic configuration of the secondary battery 1 according to this embodiment. In the following description, the direction parallel to the height direction of the secondary battery 1 is defined as the Z-axis direction, the direction parallel to the longitudinal direction of the electrode body 20 is defined as the X-axis direction, and the direction parallel to the thickness direction of the electrode body 20 is defined as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0016] 1 and 2, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 13, metal battery terminals PS, NS, and an electrode body 20. The secondary battery 1 is a sealed secondary battery in which the electrode body 20 is housed inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 13, and an electrolyte is injected into the inside of the case body 11.

[0017] [Configuration of battery case 10] As shown in Figs. 1 and 2, the battery case 10 of this embodiment is composed of a case body 11 having a generally rectangular parallelepiped shape with an opening at the top, and a sealing plate 13 that seals the opening of the case body 11. In this embodiment, both the case body 11 and the sealing plate 13 are made of aluminum, but this is not limited to this. The materials for the case body 11 and the sealing plate 13 may be appropriately selected from various metals and alloys depending on the type and application of the battery. In this embodiment, the case body 11 corresponds to the "casing" and the sealing plate 13 corresponds to the "lid".

[0018] In this embodiment, the sealing plate 13 has a shape corresponding to the shape of the opening of the case body 11, and is configured to be able to seal the opening of the case body 11. Specifically, the sealing plate 13 in this embodiment is made of a substantially rectangular flat plate member. The sealing plate 13 has a positive battery terminal PS disposed on one end side in the longitudinal direction (X-axis direction) and a negative battery terminal NS disposed on the other end side in the longitudinal direction.

[0019] Details will be described later, but in this embodiment, the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11 are laser welded, and a weld 40 consisting of multiple weld beads 41, 42, 43 is formed across the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11 (see Figures 3 and 4).

[0020] [Configuration of electrode body 20] In this embodiment, the electrode body 20 is composed of a wound body in which long strip-shaped positive and negative electrode materials are laminated with a strip-shaped separator interposed therebetween, wound, and compressed into a flat shape. As shown in FIG. 2, the electrode body 20 of this embodiment is substantially rectangular when viewed in the thickness direction (Y-axis direction), and a positive electrode terminal joint 21 in which the positive electrode material is collected is formed at one end side in the longitudinal direction (X-axis direction) when viewed in the thickness direction, and a negative electrode terminal joint 22 in which the negative electrode material is collected is formed at the other end side. The structure of the electrode body 20 is not particularly limited, and various structures used in general sealed secondary batteries can be adopted. In addition, the materials used for the positive and negative electrode materials are not particularly limited, but in this embodiment, aluminum is used for the positive electrode material and copper is used for the negative electrode material.

[0021] The electrode body 20 is housed inside the case body 11 in a position in which the thickness direction and the longitudinal direction are parallel to the horizontal direction. The electrode body 20 and the case body 11 are insulated from each other by an insulating film.

[0022] [Positive and negative electrode configurations] In this embodiment, the secondary battery 1 includes, as its positive electrode side configuration, a positive battery terminal PS consisting of a positive electrode external terminal 25 and a positive electrode current collector terminal 27, a positive electrode insulating member 29, and a positive electrode gasket 31. The secondary battery 1 also includes, as its negative electrode side configuration, a negative electrode battery terminal NS consisting of a negative electrode external terminal 26 and a negative electrode current collector terminal 28, a negative electrode insulating member 30, and a negative electrode gasket 32.

[0023] Although detailed description will be omitted, in the secondary battery 1 of this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27, and the negative electrode external terminal 26 and the negative electrode current collector terminal 28 are integrated by crimping to form the respective battery terminals PS and NS. In this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27 constituting the positive electrode battery terminal PS are both made of aluminum. Meanwhile, with regard to the negative electrode battery terminal NS, the negative electrode external terminal 26 is made of aluminum, and the negative electrode current collector terminal 28 is made of copper.

[0024] In this embodiment, the battery terminals PS, NS are provided such that the busbar welding surfaces Ba, Bb of the external terminals 25, 26 are located on the front (upper) side of the sealing plate 13, and the electrode connection portions 27a, 28a of the current collecting terminals 27, 28 are located on the back (lower) side of the sealing plate 13. In addition, the external terminals 25, 26 and the sealing plate 13, and the current collecting terminals 27, 28 and the sealing plate 13 are insulated and airtightly maintained by insulating members 29, 30 and gaskets 31, 32 made of an insulating material (e.g., PFA resin).

[0025] The current collecting terminals 27, 28 have electrode connecting portions 27a, 28a at their lower ends, and these electrode connecting portions 27a, 28a are joined to the terminal joint portions 21, 22 of the electrode body 20, respectively.

[0026] [Configuration and formation method of welded portion 40] Next, the welded portion forming step for forming the welded portion 40 and the configuration of the welded portion 40 formed through the welded portion forming step will be described with reference to Figs. 3 to 9. Fig. 3 is a top view of the secondary battery 1, which corresponds to a diagram showing a state after the third welding step, and Fig. 4 is an enlarged view of part A in Fig. 3. Fig. 5 is a schematic diagram for explaining a state after the first welding step in the welded portion forming step. Fig. 6 is a schematic diagram for explaining a second welding step performed after the first welding step, Fig. 7 is a schematic diagram for explaining a state after the second welding step, and Fig. 8 is an enlarged view of part B in Fig. 7. Furthermore, Fig. 9 is a schematic diagram for explaining a third welding step performed after the second welding step.

[0027] First, the configuration of the welded portion 40 will be described with reference to FIGS.

[0028] As shown in Figures 3 and 4, the welded portion 40 of this embodiment is composed of a first weld bead 41 formed in a first welding process described below, a second weld bead 42 formed in a second welding process, and a third weld bead 43 formed in a third welding process.

[0029] The first weld bead 41, the second weld bead 42, and the third weld bead 43 are formed at intervals from each other along the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13 in the length direction L. In this embodiment, the first weld bead 41, the second weld bead 42, and the third weld bead 43 are arranged in order along the boundary, with center lines M1, M2, and M3 along the length direction L located on the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13, center lines M1, M2, and M3 located closer to the outer peripheral edge 13a of the sealing plate 13 than the boundary, and center lines M1, M2, and M3 located closer to the opening edge 11a of the case body 11 than the boundary. That is, in this embodiment, the first weld bead 41, the second weld bead 42, and the third weld bead 43 are arranged in a staggered pattern when viewed from above.

[0030] Further, each weld bead 41, 42, 43 is arranged in a staggered manner such that center lines M1, M2, M3 along length direction L are shifted in width direction W of each weld bead 41, 42, 43 relative to center lines M1, M2, M3 of adjacent weld beads 41, 42, 43. Note that the amount of shift S in width direction W between center line M1, M2, M3 of one weld bead 41, 42, 43 and center line M1, M2, M3 of adjacent weld bead 41, 42, 43 is 10% or more and 40% or less of total widths Wa1, Wa2, Wa3 of the other weld beads 41, 42, 43.

[0031] In this embodiment, the length direction L of the weld beads 41, 42, 43 is a direction along the boundary between the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11. Therefore, for example, the length direction L of the weld beads 41, 42, 43 formed on the long side of the boundary between the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11 is a direction substantially parallel to the X-axis direction, and the length direction L of the weld beads 41, 42, 43 formed on the short side is a direction substantially parallel to the Y-axis direction.

[0032] Each weld bead 41, 42, 43 has overlapping portions D1, D2, D3 at both ends 41a, 41b, 42a, 42b, 43a, 43b in the length direction L, where the weld beads 41, 42, 43 partially overlap with the adjacent weld beads 41, 42, 43. Specifically, first weld bead 41 has overlapping portion D1 at one end 41a in the length direction L, where the first weld bead 41 overlaps with a portion of the other end 42b of second weld bead 42, and has overlapping portion D2 at the other end 41b, where the first weld bead 41 overlaps with a portion of one end 43a of third weld bead 43. Second weld bead 42 has overlapping portion D3 at one end 42a in the length direction L, where the second weld bead 42 overlaps with a portion of the other end 43b of third weld bead 43, and has overlapping portion D1 at the other end 42b. Further, third weld bead 43 has an overlapping portion D2 at one end 43a in the length direction L, and has an overlapping portion D3 at the other end 43b.

[0033] Next, the welded portion forming step will be described with reference to Fig. 3 to Fig. 9. The welded portion forming step is a step included in the method for producing the secondary battery according to this embodiment.

[0034] The weld portion forming step is a step of performing a welding step multiple times to laser-weld the opening edge portion 11a of the case body 11 and the outer peripheral edge portion 13a of the sealing plate 13 to sequentially form a plurality of weld beads 41, 42, 43 at intervals to form the weld portion 40. Specifically, in this embodiment, a total of three welding steps, a first welding step, a second welding step, and a third welding step, are performed in the weld portion forming step.

[0035] First, a first welding step is performed. In the first welding step, a laser is irradiated to the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13, and the laser irradiation position is moved a certain distance along the boundary while continuing the laser irradiation. As a result, the part irradiated with the laser melts, and a first weld bead 41 is formed. After that, the laser is irradiated again to a position spaced apart from the formed first weld bead 41, and the irradiation position is moved a certain distance while continuing the laser irradiation. This operation is repeated multiple times. As a result, as shown in FIG. 5, a plurality of first weld beads 41 are formed with intervals between each other along the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13 in the length direction L. In this embodiment, three types of first weld beads 41 are formed sequentially: one in which a center line M1 along the longitudinal direction L is located on the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13; one in which the center line M1 is located closer to the outer peripheral edge 13a of the sealing plate 13 than the above-mentioned boundary; and one in which the center line M1 is located closer to the opening edge 11a of the case body 11 than the above-mentioned boundary.

[0036] Next, the second welding step is performed. In the second welding step, as shown in FIG. 6, a laser is irradiated to a start position Ps1, and the laser irradiation position is moved along the boundary portion to an end position Pe1 while continuing the laser irradiation. The start position Ps1 is a position spaced apart from one end 41a of the first weld bead 41 along the boundary portion, and the center is shifted by a shift amount S in the width direction W of the first weld bead 41 with respect to a center line M1 along the length direction L of the first weld bead 41 in a top view. The end position Pe1 is a position that partially overlaps with one end 41a of the first weld bead 41 in the length direction L in a top view, and is a position that is shifted by a shift amount S in the width direction W of the first weld bead 41 with respect to the center line M1 of the first weld bead 41, similarly to the start position Ps1. Incidentally, deviation amount S in the second welding process is set to a value within a range of 10% to 40%, more preferably 30% to 40%, of total width Wa1 of first weld bead 41 that has already been formed.

[0037] By performing the second welding step, as shown in Fig. 7 and Fig. 8, a plurality of second weld beads 42 are formed at intervals along the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13 in the length direction L. In the second welding step, the output of the laser and the like are adjusted so that the overall width Wa2 of the second weld bead 42 is substantially the same as the overall width Wa1 of the first weld bead 41. In the present embodiment, similarly to the first weld bead 41, the second weld beads 42 are also formed in three types in sequence: one in which the center line M2 along the length direction L is located on the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13, one in which the center line M2 is located closer to the outer peripheral edge 13a of the sealing plate 13 than the boundary, and one in which the center line M2 is located closer to the opening edge 11a of the case body 11 than the boundary.

[0038] Here, in the second welding step, the start position Ps1 and end position Pe1 of the laser irradiation are set as positions whose centers are shifted by a shift amount S in the width direction W of the first weld bead 41 with respect to the center line M1 along the length direction L of the first weld bead 41 in a top view. In addition, the end position Pe1 is set so as to partially overlap one end 41a of the first weld bead 41 in the length direction L in a top view. Therefore, as shown in FIG. 7 and FIG. 8, the second weld bead 42 is formed in which the center line M2 is shifted by the shift amount S with respect to the center line M1 of the first weld bead 41, and the first weld bead 41 and the second weld bead 42 are arranged in a staggered pattern. In addition, an overlapping portion D1 is formed at the other end 42b of the second weld bead 42 in the length direction L, which partially overlaps with one end 41a of the first weld bead 41.

[0039] Next, a third welding step is performed. In the third welding step, as shown in FIG. 9, a laser is irradiated to a start position Ps2, and the laser irradiation position is moved along the boundary portion to an end position Pe2 while continuing the laser irradiation. The start position Ps2 is a position that partially overlaps with the other end 41b of the first weld bead 41 in the length direction L in a top view, while the end position Pe2 is a position that partially overlaps with one end 42a of the second weld bead 42 in the length direction L in a top view. In addition, the start position Ps2 and the end position Pe2 are both positions whose centers are shifted by a shift amount S in the width direction W of the first weld bead 41 and the second weld bead 42 with respect to the center line M1 of the first weld bead 41 and the center line M2 of the second weld bead 42. The deviation amount S in the third welding process is set to a value within the range of 10% to 40% of the overall width Wa1 of the first weld bead 41 and the overall width Wa2 of the second weld bead 42 that have already been formed, more preferably within the range of 30% to 40%.

[0040] By performing the third welding step, as shown in Figs. 8 and 9, a plurality of third weld beads 43 are formed at intervals along the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13 in the length direction L. In the third welding step, the output of the laser and the like are adjusted so that the Wa3 of the third weld bead 43 is substantially the same as the overall width Wa1 of the first weld bead 41 and the overall width Wa2 of the second weld bead 42. In the present embodiment, similarly to the first weld bead 41 and the second weld bead 42, the third weld bead 43 is also formed in three types in sequence: one in which the center line M3 along the length direction L is located on the boundary between the opening edge 11a of the case body 11 and the outer peripheral edge 13a of the sealing plate 13, one in which the center line M3 is located closer to the outer peripheral edge 13a of the sealing plate 13 than the boundary, and one in which the center line M3 is located closer to the opening edge 11a of the case body 11 than the boundary.

[0041] In the third welding step, start position Ps2 and end position Pe2 of laser irradiation are set as positions whose centers are shifted by a shift amount S in width direction W of first weld bead 41 and second weld bead 42 in a top view. Start position Ps2 is set to partially overlap other end 41b of first weld bead 41, and end position Pe2 is set to partially overlap one end 42a of second weld bead 42. Therefore, as shown in Figs. 8 and 9, third weld bead 43 is formed whose center line M3 is shifted by shift amount S with respect to center line M1 of first weld bead 41 and center line M2 of second weld bead 42, and each of weld beads 41, 42, and 43 is arranged in a staggered pattern. In addition, an overlap portion D2 is formed at one end 43a of the third weld bead 43 in the longitudinal direction L, which partially overlaps with the other end 41b of the first weld bead 41, and an overlap portion D3 is formed at the other end 43b, which partially overlaps with one end 42a of the second weld bead 42.

[0042] The movement distance of the laser irradiation position when forming each weld bead 41, 42, 43 may be appropriately set so that the first weld bead 41, the second weld bead 42, and the third weld bead 43 weld the entire circumference of the boundary between the opening edge 11a of the case body 11 and the outer periphery 13a of the sealing plate 13. If the movement distance is too long, damage due to heat input increases, and if it is too short, the number of welding operations increases, making the work complicated. Therefore, for example, it is preferable that the movement distance is such that the length of each weld bead 41 is 2% to 5% of the entire circumference of the boundary between the opening edge 11a of the case body 11 and the outer periphery 13a of the sealing plate 13. In addition, the movement speed of the laser is not particularly limited as long as it is a speed at which appropriate welding can be performed.

[0043] As described above, in this embodiment, one welding process is performed so that center lines M1, M2, M3 along the length direction L of weld beads 41, 42, 43 formed in the one welding process are shifted in a width direction W perpendicular to the length direction L of weld beads 41, 42, 43 formed in another welding process relative to center lines M1, M2, M3 along the length direction L of adjacent weld beads 41, 42, 43 formed in the other welding process, and overlapping portions D1, D2, D3 are formed at both ends in the length direction L of each weld bead 41, 42, 43.

[0044] When forming a plurality of weld beads arranged in a straight line, each weld bead is formed such that its end overlaps with the end of an adjacent weld bead over the entire width of the weld bead, and therefore the entire width of the end of the already formed weld bead becomes a re-welded area.

[0045] In contrast, in this embodiment, for example, when the second welding step is performed after the first welding step, second weld bead 42 is formed such that other end 42b overlaps with one end 41a of adjacent, already formed first weld bead 41 in part in width direction W. That is, in this case, only a part of one end 41a of already formed first weld bead 41 in width direction W becomes a re-welded portion.

[0046] Therefore, in the manufacturing method of secondary battery 1 according to this embodiment, the number of re-welded portions is reduced and the occurrence of welding defects is suppressed when forming multiple weld beads 41, 42, 43 in a straight line compared to when multiple weld beads 41, 42, 43 are formed in a straight line. Therefore, secondary battery 1 has improved quality of welded portion 40 compared to a battery in which multiple weld beads are arranged in a straight line.

[0047] Furthermore, according to the method for manufacturing the secondary battery 1 according to this embodiment, the weld beads 41, 42, 43 are arranged in a staggered pattern when viewed from above, and the weld length is increased. This reduces stress against external forces such as internal pressure, and increases the durability of the welded portion 40 in the secondary battery 1. In other words, the secondary battery 1 according to this embodiment has a highly durable welded portion 40.

[0048] Furthermore, according to the manufacturing method of the secondary battery 1 according to this embodiment, the welding step of forming a plurality of weld beads by a plurality of laser weldings is performed a plurality of times to form the welded portion 40. Therefore, compared with a method of forming a welded portion by a single laser welding, the cooling of the welded portion is slower, and weld cracks due to rapid cooling can be prevented. Therefore, in the secondary battery 1, the welding strength between the case body 11 and the sealing plate 13 is high. In addition, since the time required for one laser welding is shortened, the amount of heat transferred to components such as the resin members (insulating members 29, 30 and gaskets 31, 32) attached to the sealing plate 13 and the battery terminals PS, NS can be reduced. Therefore, melting and thermal settling of the resin members due to heat generated during welding and deterioration of the battery terminals are suppressed, and the performance degradation of the secondary battery 1 caused by these factors can be suppressed.

[0049] That is, according to the method for manufacturing the secondary battery 1 according to this embodiment, it is possible to suitably manufacture the secondary battery 1 having the welded parts 40 with high quality and high durability.

[0050] [Another embodiment] [1] In the above embodiment, a mode in which a total of three welding steps, namely, the first welding step, the second welding step, and the third welding step, are performed in the welded portion forming step has been described, but the present invention is not limited to such a mode. It is sufficient that at least two welding steps are performed in the welded portion forming step. FIG. 10 is a top view showing a secondary battery 50 according to another embodiment. FIG. 11 is a top view showing a secondary battery 60 according to another embodiment. For example, as shown in FIG. 10 and FIG. 11, a total of two welding steps, a first welding step and a second welding step, may be performed so that the first weld beads 41 and the second weld beads 42 are arranged in a staggered pattern when viewed from above. Even in such an embodiment, the number of re-welded locations is reduced, suppressing the occurrence of welding defects, and the durability of the welded portion 40 is improved by increasing the weld length. Therefore, secondary batteries 50, 60 having high quality and highly durable welded portions 40 can be suitably manufactured.

[0051] [2] In the above embodiment, first weld bead 41, second weld bead 42, and third weld bead 43 are arranged in a staggered pattern when viewed from above, but the present invention is not limited to this. As long as at least some of the weld beads constituting the welded portion are arranged in a staggered pattern when viewed from above, the weld beads formed in each welding process may not be arranged in a staggered pattern when viewed from above. For example, as shown in Fig. 10, a plurality of first weld beads 41 and a plurality of second weld beads 42 may be arranged side by side on a straight line, and the weld beads 41, 42 may be arranged in a staggered pattern as a whole in the welded portion. In Fig. 10, a plurality of first weld beads 41 are arranged side by side on a straight line such that a center line M1 is located closer to the outer peripheral edge 13a of sealing plate 13 than the boundary between opening edge 11a of case body 11 and outer peripheral edge 13a of sealing plate 13. A plurality of second weld beads 42 are arranged side by side on a straight line such that a center line M2 is located closer to the opening edge 11a of case body 11 than the boundary. 11, a plurality of first weld beads 41 may be arranged in a straight line, a plurality of second weld beads 42 may be arranged in a staggered pattern, and a plurality of weld beads 41, 42 may be arranged in a staggered pattern as a whole of the welded portion. In FIG. 11, a plurality of first weld beads 41 are arranged in a straight line such that center line M1 is located on the boundary. Meanwhile, a plurality of second weld beads 42 are arranged in a staggered pattern such that one whose center line M2 is located closer to outer peripheral edge portion 13a of sealing plate 13 than the boundary and one whose center line M2 is located closer to opening edge portion 11a of case body 11 than the boundary are alternately arranged.

[0052] [3] In the above embodiment, the weld beads 41, 42, 43 constituting the welded portion 40 are arranged in a staggered pattern in a top view around the entire boundary between the opening edge 11a of the case body 11 and the outer circumferential edge 13a of the sealing plate 13. However, the present invention is not limited to this. A plurality of weld beads may be formed around the entire boundary, with some of them arranged in a staggered pattern in a top view and the rest arranged in a straight line along the boundary.

[0053] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0054] 1: Secondary battery 11: Case body (housing) 11a: Outer periphery 13: Sealing plate (lid body) 13a: Opening edge 20: Electrode body 41: First weld bead 41a: One end (end) 41b: Other end (end) 42: Second weld bead 42a: One end (end) 42b: Other end (end) 43: 3rd weld bead 43a: One end (end) 43b: Other end (end) D1, D2, D3: Overlapping parts L: Length direction M1,M2,M3: Center line S: Displacement amount

Claims

1. A method for manufacturing a secondary battery including a housing having an opening and housing an electrode assembly therein, and a lid that seals the opening of the housing, comprising the steps of: a welded portion forming step of performing a welding step of laser-welding an opening edge portion of the housing and an outer peripheral edge portion of the lid body to sequentially form a plurality of weld beads at intervals at least twice to form a welded portion; In the weld portion forming step, one welding step is performed such that a center line along the length direction of the weld bead formed in the one welding step is shifted in a width direction perpendicular to the length direction of the weld bead formed in the other welding step with respect to a center line along the length direction of an adjacent weld bead formed in the other welding step, and the weld bead formed in the one welding step has overlapping portions at both ends in the length direction where the weld bead formed in the other welding step partially overlaps with the weld bead formed in the other welding step, thereby forming the weld portion at least a portion of which is constituted by a plurality of the weld beads arranged in a staggered pattern; a deviation between a center line along the length direction of the weld bead formed in one welding process and a center line along the length direction of the weld bead formed in another welding process is a value within a range of 10% to 40% of a total width of the weld bead formed in the other welding process.

2. A housing having an opening and housing an electrode body therein; a cover that seals the opening of the housing, a weld portion formed by laser welding an opening edge portion of the housing and an outer circumferential edge portion of the lid body, the weld portion being composed of a plurality of weld beads; at least some of the plurality of weld beads are arranged in a staggered pattern in which a center line along the length direction of one of the weld beads is shifted in a width direction perpendicular to the length direction of the other adjacent weld bead with respect to a center line along the length direction of the other adjacent weld bead, and one of the weld beads has overlapping portions at both ends in the length direction that partially overlap with the other adjacent weld bead, A secondary battery, wherein the amount of deviation between a center line along the length direction of one of the weld beads and a center line along the length direction of another adjacent weld bead is a value within a range of 10% to 40% of the overall width of the other adjacent weld bead.

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