Battery cell and method for manufacturing the same

Abstract

To provide a highly reliable battery cell in which generation of blow holes in a welded part is suppressed, and a method for manufacturing the battery cell.SOLUTION: A method for manufacturing a battery cell includes steps of: storing an electrode body in a case body with an opening; providing a sealing plate with an external edge in the opening of the case body; and welding the case body and the external edge of the sealing plate to each other and sealing the opening. A slope part in which the welding depth increases in a welding progress direction in a welding start part is formed, and the length of the slope part along the progress direction is at least 1 mm and 5 mm at a maximum.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present technology relates to a battery cell and a method for manufacturing the same. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 09-007560 (Patent Document 1) discloses that when laser welding a cover plate (sealing plate) to an outer can (case body), the input energy of the laser beam is gradually reduced to terminate the laser welding once the laser beam has made a circuit around the mating portion and returned to the welding start point, thereby reducing welding defects caused by reheating in the overlap portion in the final stage of sealing welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-007560 Summary of the Invention [Problem to be solved by the invention]

[0004] In the welded seal, air trapped around the weld can enter the molten part and cause blowholes. As the capacity of batteries increases, more effective measures against this problem are required. For example, as the thickness of the sealing plate increases, it is necessary to increase the welding output and deepen the welding depth, which increases the need to effectively suppress the occurrence of blowholes caused by reheating of the air trapped between the fracture surface of the sealing plate and the inner surface of the case body.

[0005] An object of the present technology is to provide a highly reliable battery cell in which the occurrence of blowholes in welded joints is suppressed, and a manufacturing method thereof. [Means for solving the problem]

[0006] The present technology provides the following battery cell and method for manufacturing the same.

[0007] [1] A method for manufacturing a battery cell, comprising the steps of: accommodating an electrode body in a case body having an opening; providing a sealing plate having an outer edge in the opening of the case body; and welding the case body and the outer edge of the sealing plate to seal the opening, wherein a slope portion is formed at a start of the welding, the weld depth increasing in a direction in which the welding proceeds, and the length of the slope portion along the proceeding direction is 1 mm or more and 5 mm or less.

[0008] [2] The method for manufacturing a battery cell according to [1], wherein the welding is terminated after passing the starting portion.

[0009] [3] The method for manufacturing a battery cell described in [1] or [2], wherein the case body has a generally rectangular shape, the sealing plate has a generally rectangular shape having a long side and a short side, the length of the long side of the sealing plate is 250 mm or more and 400 mm or less, the length of the short side of the sealing plate is approximately 30 mm or more and 50 mm or less, and the thickness of the sealing plate is 2 mm or more and 3 mm or less.

[0010] [4] The method for manufacturing a battery cell according to any one of [1] to [3], wherein the maximum depth of the welding is 0.8 mm or more and 3 mm or less.

[0011] [5] A battery cell comprising: a case body having an opening and housing an electrode body; a sealing plate having an outer edge and provided at the opening; and a welded portion joining the case body and the outer edge of the sealing plate, wherein in a cross section along the direction in which the welding that constitutes the welded portion proceeds, a triangular band is formed near the start of the welding, and the angle of the apex of the triangular band is between 100° and 140°.

[0012] [6] The battery cell described in [5], wherein the case body has a generally rectangular shape, the sealing plate has a generally rectangular shape having a long side and a short side, the length of the long side of the sealing plate is 250 mm or more and 400 mm or less, the length of the short side of the sealing plate is 30 mm or more and 50 mm or less, and the thickness of the sealing plate is 2 mm or more and 3 mm or less.

[0013] [7] The battery cell according to [5] or [6], wherein the maximum depth of the weld is 0.8 mm or more and 3 mm or less. Effect of the Invention

[0014] According to the present technology, it is possible to provide a highly reliable battery cell in which the occurrence of blowholes in welded parts is suppressed, and a method for manufacturing the same. [Brief description of the drawings]

[0015] [Figure 1] FIG. [Diagram 2] 4 is a cross-sectional view showing a welded portion between a case body and a sealing plate. FIG. [Diagram 3] FIG. 1 is a schematic diagram showing a laser welding machine. [Figure 4] FIG. 1 illustrates a beam used in laser welding. [Diagram 5] FIG. 4 is a schematic diagram showing a welding start portion and a welding end portion. [Figure 6] 10 is a cross-sectional view for explaining air trapping at the start and end of welding. FIG. [Figure 7] This is a schematic diagram (part 1) of a cross section at the welding travel position. [Figure 8] This is a schematic diagram of the cross section at the welding travel position (part 2). [Figure 9] FIG. 13 is a diagram for explaining the slope length (D) at the start of welding. [Figure 10] FIG. 1 is a graph showing the relationship between the slope length (D) and the blowhole occurrence rate. [Figure 11]FIG. 13 is a diagram showing the relationship between the slope length (D) and the angle of the apex of the triangular band formed in the sealed portion after welding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof will not be repeated.

[0017] In the embodiments described below, when referring to the number, amount, etc., the scope of the present technology is not necessarily limited to the number, amount, etc., unless otherwise specified. In addition, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. In addition, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiment.

[0018] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

[0019] Furthermore, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along" are used in this specification, these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in one state, and the relative positional relationships can be inverted or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0020] In this specification, the term "battery" is not limited to lithium ion batteries, but may include other batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0021] In this specification, a "battery cell" can be mounted in a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), etc. However, the use of the "battery cell" is not limited to being mounted in a vehicle.

[0022] 1 is an exploded perspective view of a battery cell. As shown in FIG. 1, the battery cell according to this embodiment includes a case body 1, a cover member 2, and an electrode body 3.

[0023] The case body 1 has an opening 11 that opens upward. The opening 11 is defined by a side surface 12. An electrolyte (not shown) is accommodated inside the case body 1 together with the electrode body 3. The case body 1 has a substantially rectangular parallelepiped shape including a long side surface 12A and a short side surface 12B.

[0024] The cover member 2 includes a positive electrode side current collector 21, a negative electrode side current collector 22, and a sealing plate 23 that seals the opening 11 of the case body 1. An electrode terminal 20A is provided on the sealing plate 23. The electrode terminal 20A includes a positive electrode external terminal 21A and a negative electrode external terminal 22A that are provided at a distance from each other in the X-axis direction. The positive electrode side current collector 21 is electrically connected to the positive electrode external terminal 21A. The negative electrode side current collector 22 is electrically connected to the negative electrode external terminal 22A.

[0025] The sealing plate 23 has a generally rectangular shape having a longitudinal direction (X-axis direction) and a lateral direction (Y-axis direction). As an example, the length (L1) of the longitudinal direction of the sealing plate 23 is about 250 mm or more and 400 mm or less. As an example, the length (L2) of the lateral direction of the sealing plate 23 is about 30 mm or more and 50 mm or less. As an example, the thickness (T) of the sealing plate 23 is about 2 mm or more and 3 mm or less.

[0026] The electrode body 3 has a positive electrode 31 and a negative electrode 32 aligned in the X-axis direction (longitudinal direction). The current collector 21 is connected to the positive electrode 31 of the electrode body 3, and the current collector 22 is connected to the negative electrode 32 of the electrode body 3. This electrically connects the positive electrode 31 and the negative electrode 32 of the electrode body 3 to the positive electrode external terminal 21A and the negative electrode external terminal 22A of the cover member 2.

[0027] When manufacturing a battery cell, after connecting the current collectors 21, 22 to the positive electrode 31 and the negative electrode 32, the electrode body 3 is housed in the case body 1 through the opening 11, and the sealing plate 23 is provided in the opening 11 of the case body 1. Then, the outer edge of the case body 1 and the sealing plate 23 are joined by laser welding to seal the opening 11.

[0028] Next, a non-aqueous electrolyte is injected through an injection hole (not shown) provided in the sealing plate 23. The non-aqueous electrolyte may contain, for example, ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). After the non-aqueous electrolyte is injected, the injection hole is sealed with a sealing member (not shown). By carrying out the above steps, the battery cell is completed.

[0029] The structure of the battery cell is not limited to that shown in Fig. 1, and for example, the electrode body 3 may have a tab protruding in the Z-axis direction. The electrode body 3 may be a wound type electrode body or a laminated type electrode body. The battery case is not limited to a rectangular shape.

[0030] 2 is a cross-sectional view showing a welded portion 40 between the side surface 12 of the case body 1 and the sealing plate 23. The "welding travel position" in FIG. 2 is a position corresponding to the center of the welding beam. The side surface (plate thickness surface) of the sealing plate 23 includes a fracture surface 23A and a shear surface 23B formed when the plate-shaped member is punched to extract the sealing plate 23. As shown in FIG. 2, an air-trapping region is formed between the fracture surface 23A and the side surface 12 of the case body 1, which can cause the occurrence of blowholes.

[0031] The welding depth of the welded portion 40 varies depending on the output of the laser welding and the plate thickness of the sealing plate 23, but as an example, the maximum welding depth is about 0.8 mm or more and 3 mm or less.

[0032] 3 is a schematic diagram showing a laser welding machine 100. The laser welding machine 100 includes a laser irradiation unit 110 and a scanner 120. The scanner 120 identifies a position to be irradiated with laser light, and the laser irradiation unit 110 irradiates the laser light toward the identified position.

[0033] Fig. 4 is a diagram showing the beam 111. As shown in Fig. 4, the beam 111 includes a core beam 111A and a ring beam 111B.

[0034] The outer diameter and output of the core beam 111A can be changed as appropriate, but as an example, the outer diameter of the core beam 111A is about 0.25 mm or more and 0.35 mm or less, and the output of the core beam 111A is about 1700 W or more and 2300 W or less.

[0035] Also, as an example, the outer diameter of the ring beam 111B is about 0.76 mm or more and 0.99 mm or less, and the output of the ring beam 111B is about 3900 W or more and 5300 W or less.

[0036] The scanning speed of the beam 111 in laser welding can be changed as appropriate, but as an example, it is about 220 mm / s or more and 410 mm / s or less.

[0037] Fig. 5 is a schematic diagram showing the start and end of welding. As shown in Fig. 5, the laser welding proceeds from a welding start point O (start point) in the direction of arrow A, goes around the outer edge of the rectangular sealing plate 23, passes the welding start point O, proceeds in the direction of arrow B, and ends (end of welding).

[0038] In the example of Figure 5, the welding start point O is a position on the front side (-Y side) and a distance L1 (for example, about 10 mm) from the center of the sealing plate 23 in the Y-axis direction, and the welding end point is a position on the back side (+Y side) and a distance L2 (for example, about 20 mm) from the center of the sealing plate 23 in the Y-axis direction.

[0039] Next, air trapping at the start and end of welding will be described with reference to FIG.

[0040] 6 shows a state in which laser welding is started in the direction of arrow DR1 from welding start point O, goes around the outer edge of sealing plate 23, and returns in the direction of arrow DR2 to the vicinity of welding start point O. Welded portion 40 includes a first portion 41 where molten metal has solidified and a second portion 42 that is still in a molten state. In the vicinity of welding start point O, an air-trapped region is formed between a rear end surface 43 of first portion 41 at the welding start portion and a front end surface 44 of second portion 42 that is in a molten state, and this air may enter second portion 42 that is in a molten state, causing blowholes.

[0041] Fig. 7 and Fig. 8 are schematic diagrams created based on cross-sectional photographs showing the state after welding at the welding travel position, and Fig. 9 is a diagram for explaining the slope length (D) at the start of welding.

[0042] 9, the laser output or welding depth is gradually increased from the welding start point O toward the welding progress direction, and the laser output is set to 100% when the position is reached at a distance D from the welding start point O. As a result, during the welding process, a slope portion in which the welding depth gradually increases is formed in the range from the welding start point O to the distance D. In this specification, the distance D is referred to as the "slope length (D)."

[0043] Fig. 7 shows a cross section when the slope length (D) is 1 mm, and Fig. 8 shows a cross section when the slope length (D) is 20 mm. As shown in Figs. 7 and 8, in the cross section along the direction of welding after sealing off the weld, a triangular band having a shape according to the slope length (D) is formed near the welding start point O. θ1 shown in Fig. 7 (D = 1 mm) is about 110°, and θ2 shown in Fig. 8 (D = 20 mm) is about 170°.

[0044] Fig. 10 is a diagram showing the relationship between the slope length (D) and the blowhole incidence rate. Fig. 11 is a diagram showing the relationship between the slope length (D) and the angle of the apex of the triangular band formed in the sealed portion after welding.

[0045] The results shown in Figures 10 and 11 were evaluated or measured under the conditions of the outer diameter, output, and scanning speed of the beam 111 (core beam 111A and ring beam 111B) described above, and "A2" in Figure 10 shows the results when the output was increased by 20% compared to "A1".

[0046] As shown in Figure 10, under both conditions "A1" and "A2," when the slope length (D) is between 10mm and 20mm, blowholes occur at a certain rate, whereas when the slope length (D) is between 1mm and 5mm, the occurrence of blowholes is suppressed. Also, when the slope length (D) is 20mm, the probability of blowhole occurrence is higher than when the slope length (D) is 10mm.

[0047] The tendency shown in FIG. 10 is believed to arise because, as the slope length (D) becomes longer, the air trapping area (FIG. 6) between the rear end face 43 of the first portion 41 at the start of the weld and the front end face 44 of the second portion 42 in a molten state becomes larger, and the amount of air trapped becomes larger.

[0048] As shown in Fig. 11, the longer the slope length (D), the larger the angle θ of the apex of the triangular band formed near the welding start point O in the cross section along the welding progress direction after the weld is sealed off. When the slope length (D) is 1 mm to 5 mm, which suppresses the occurrence of blowholes, the angle θ is about 100° to 140°.

[0049] 10 and 11, in the laser welding process of the case body 1 and the sealing plate 23, the slope length (D) from the welding start point O is preferably about 1 mm or more and 5 mm or less. Also, in a cross section along the welding progress direction after the welding is sealed off, the angle θ of the apex of the triangular band formed in the vicinity of the welding start point O is preferably about 100° or more and 140° or less.

[0050] According to the battery cell manufacturing method (laser welding method) of the present embodiment, it is possible to suppress the occurrence of blowholes in the welded portion and provide a highly reliable battery cell.

[0051] Although the embodiment of the present technology has been described above, the embodiment disclosed herein should be considered as illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0052] 1 case body, 2 cover member, 3 electrode body, 11 opening, 12 side surface, 12A long side surface, 12B short side surface, 20A electrode terminal, 21, 22 current collector, 21A positive electrode external terminal, 22A negative electrode external terminal, 23 sealing plate, 23A fracture surface, 23B shear surface, 31 positive electrode, 32 negative electrode, 40 welded portion, 41 first portion, 42 second portion, 43 rear end surface, 44 front end surface, 100 laser welding machine, 110 laser irradiation portion, 111 beam, 111A core beam, 111B ring beam, 120 scanner.

Claims

1. A step of housing the electrode body in a case body having an opening; providing a sealing plate having an outer edge at the opening of the case body; and welding the case body and the outer edge of the sealing plate to seal the opening. A slope portion is formed at the start portion of the welding, in which the welding depth increases in the direction in which the welding proceeds; The method for manufacturing a battery cell, wherein the length of the slope portion along the traveling direction is 1 mm or more and 5 mm or less.

2. The method of claim 1 , wherein the welding ends after passing the start portion.

3. The case body has a substantially rectangular parallelepiped shape, The sealing plate has a generally rectangular shape having a long side direction and a short side direction, The length of the sealing plate in the longitudinal direction is 250 mm or more and 400 mm or less, The length of the sealing plate in the short side direction is about 30 mm or more and 50 mm or less, The method for manufacturing a battery cell according to claim 1 or 2, wherein the sealing plate has a thickness of 2 mm or more and 3 mm or less.

4. The method for manufacturing a battery cell according to claim 1 or 2, wherein the maximum depth of the welding is 0.8 mm or more and 3 mm or less.

5. A case body having an opening and housing the electrode body; a sealing plate having an outer edge and provided at the opening; a welded portion that joins the case body and the outer edge of the sealing plate, In a cross section along the direction of welding that forms the welded portion, a triangular band is formed near the start of the welding, The angle of the apex of the triangular band is equal to or greater than 100° and equal to or less than 140°.

6. The case body has a substantially rectangular parallelepiped shape, The sealing plate has a generally rectangular shape having a long side direction and a short side direction, The length of the sealing plate in the longitudinal direction is 250 mm or more and 400 mm or less, The length of the sealing plate in the short side direction is 30 mm or more and 50 mm or less, The battery cell according to claim 5 , wherein the sealing plate has a thickness of 2 mm or more and 3 mm or less.

7. The battery cell according to claim 5 or claim 6, wherein the maximum depth of the weld is 0.8 mm or more and 3 mm or less.

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