Battery cell and method for manufacturing battery cell

Abstract

A battery cell (10) is provided with: a battery element (100); a front cover (210) that covers an end portion of the battery element (100); and an exterior film (300) wound around the battery element (100) and the front cover (210). The front cover (210) has a front protrusion (212) protruding toward the opposite side of the battery element (100) of the front cover (210). The front protrusion (212) and the exterior film (300) are at least partially joined to each other.

Description

Technical Field

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

[0002] In recent years, various battery cell structures, such as lithium-ion secondary battery cells, have been developed. For example, the battery cell described in Patent Document 1 comprises a battery element, two cover members, and an exterior film. The two cover members cover both ends of the battery element in the longitudinal direction. The exterior film is wrapped around the longitudinal direction of the battery element.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2021 / 157731 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] For example, in the battery cell described in Patent Document 1, the cover and the outer film are sometimes joined together by heat welding. However, simply applying heat to the cover and the outer film may not sufficiently increase the joint strength between the cover and the outer film. If the joint strength between the cover and the outer film is insufficient, it may be difficult to improve the sealing performance of the battery cell.

[0008] One example of an object of the present invention is to improve the sealing performance of a battery cell. Other objects of the present invention will become apparent from the description of this specification.

[0009] Means for solving problems

[0010] One embodiment of the present invention is as follows. [1]

[0012] A battery cell comprises: a battery element; a cover covering an end of the battery element; and an outer film wrapped around the battery element and the cover, wherein the cover has a protrusion protruding toward the side of the cover opposite to the battery element, and the protrusion and the outer film are at least partially joined to each other. [2]

[0014] The battery cell according to [1], wherein the protrusion at least partially surrounds a given area on the opposite side of the battery element relative to the cover member. [3]

[0016] The battery cell according to [1] or [2], wherein the fusion zone of at least one of the protrusion and the exterior film is at least partially present between the protrusion and the exterior film. [4]

[0018] A method for manufacturing a battery cell comprises: wrapping an exterior film around a battery element and a cover having a protrusion protruding toward the opposite side of the battery element and covering an end of the battery element; and at least partially joining the protrusion and the exterior film to each other. [5]

[0020] According to the method for manufacturing a battery cell described in [4], the step of at least partially joining the protrusion and the exterior film to each other includes the step of applying heat from a portion of the exterior film opposite to the protrusion and a portion of the protrusion opposite to the exterior film.

[0021] Effects of the Invention

[0022] According to the above aspect of the present invention, the sealing performance of the battery cell can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a front perspective view of a battery cell according to the embodiment.

[0024] Figure 2 This is an enlarged front perspective view of a portion of a battery cell according to the embodiment.

[0025] Figure 3 It is a front view of a battery cell according to the embodiment.

[0026] Figure 4 It is a right side view of the battery cell according to the embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[0028] Figure 1 It is a front perspective view of the battery cell 10 according to the embodiment. Figure 2 This is an enlarged front perspective view of a portion of the battery cell 10 according to the embodiment. Figure 3 It is a front view of the battery cell 10 according to the embodiment. Figure 4 1 is a right side view of the battery cell 10 according to the embodiment. Figure 4 In the figure, for the purpose of explanation, the exterior film 300 described later is shown through. Figure 4 In the figure, for the sake of explanation, a base end or rear end of a front protrusion 212 described later and a base end or front end of a rear protrusion 222 described later are shown by dotted lines.

[0029] In each figure, the X, Y, and Z directions are indicated for illustrative purposes. The X direction indicates the front-to-back direction of the battery cell 10. The Y direction is perpendicular to the X direction. The Y direction indicates the left-to-right direction of the battery cell 10. The Z direction is perpendicular to both the X and Y directions. The Z direction indicates the up-down direction of the battery cell 10. The directions indicated by the arrows indicating the X direction, the Y direction, and the Z direction are the rear direction, the left direction, and the upward direction, respectively. The relationships among the X, Y, Z, front-to-back direction, left-to-right direction, and up-down direction of the battery cell 10 are not limited to this example.

[0030] In addition, a white circle with an X indicating the X direction, the Y direction, or the Z direction means that the direction from the front to the back of the paper is the direction indicated by the arrow indicating the direction.

[0031] The battery cell 10 includes a battery element 100 , a positive electrode tab 110 , a negative electrode tab 120 , a front cover 210 , a rear cover 220 , and an exterior film 300 . The exterior film 300 includes a wrapping portion 302 and a lead portion 304 .

[0032] The battery element 100 has a roughly rectangular parallelepiped shape. The long side of the battery element 100 is roughly parallel to the X direction. The length of the battery element 100 in the X direction is not limited to the following, and for example, it is 300 mm or more and 500 mm or less, preferably 450 mm or less. The short side of the battery element 100 is roughly parallel to the Z direction. The length of the battery element 100 in the Z direction is not limited to the following, and for example, it is 90 mm or more and 130 mm or less, preferably 120 mm or less. The thickness direction of the battery element 100 is roughly parallel to the Y direction. The thickness of the battery element 100 in the Y direction is not limited to the following, and for example, it is 20 mm or more and 50 mm or less, preferably 45 mm or less. However, the shape of the battery element 100 is not limited to this example.

[0033] The battery element 100 includes at least one positive electrode (not shown), at least one negative electrode (not shown), and at least one separator (not shown). For example, multiple positive electrodes and multiple negative electrodes are alternately stacked in the Y direction. At least a portion of the separator is located between adjacent positive electrodes and negative electrodes in the Y direction. For example, multiple sheet-shaped separators may be located between adjacent positive electrodes and negative electrodes in the Y direction. Alternatively, a sheet-shaped separator may be formed in a zigzag shape passing through the area between adjacent positive electrodes and negative electrodes in the Y direction. Alternatively, the positive electrode, negative electrode, and separator may be wound so that the separator is arranged between the positive electrode and the negative electrode. In one example, the positive electrode, negative electrode, and separator are wound with both sides of one of the positive electrode and negative electrode covered by the separator. In other examples, a stack comprising multiple unit stacks may be wound, wherein the unit stacks include the positive electrode, separator, and negative electrode in this order. The winding structure of the positive electrode, negative electrode, and separator is not limited to these examples.

[0034] In the embodiment, battery cell 10 is a battery cell containing an electrolyte. However, battery cell 10 may also be an all-solid-state battery. In an all-solid-state battery, a solid electrolyte layer is provided in the portion corresponding to the separator. An all-solid-state battery does not contain an electrolyte. Unless otherwise specified, the battery cell 10 will be described as a battery cell containing an electrolyte.

[0035] like Figure 4 As shown, the positive electrode tab 110 is located in front of the battery element 100. The rear end of the positive electrode tab 110 is electrically connected to the positive electrode current collector 102a. The positive electrode current collector 102a extends forward from the positive electrode 102. Thus, the positive electrode tab 110 is electrically connected to the plurality of positive electrodes 102.

[0036] like Figure 4 As shown, the negative electrode tab 120 is located at the rear of the battery element 100. The front end of the negative electrode tab 120 is electrically connected to the negative electrode current collector 104a. The negative electrode current collector 104a extends rearward from the negative electrode 104. Thus, the negative electrode tab 120 is electrically connected to the plurality of negative electrodes 104.

[0037] The front cover 210 covers the front end of the battery element 100. The front cover 210 is made of, for example, resin, metal, or the like. The front end of the positive electrode tab 110 protrudes from the front of the front cover 210. Viewed from the front, the front cover 210 has a roughly rectangular shape with rounded corners in the X direction. Viewed from the front, the long side of the front cover 210 is roughly parallel to the Z direction, and the short side of the front cover 210 is roughly parallel to the Y direction. The four corners of the front cover 210 in the X direction are aligned with the four corners of the battery element 100 in the X direction.

[0038] like Figures 1 to 4As shown, the front cover 210 has a front protrusion 212. The front protrusion 212 protrudes toward the side of the front cover 210 opposite to the battery element 100. That is, the front protrusion 212 protrudes in front of the front cover 210. In an embodiment, the front protrusion 212 at least partially surrounds a predetermined area in front of the front cover 210 in the X direction when viewed from the front. In an embodiment, the positive electrode tab 110 is provided in the predetermined area. Figure 3 In the illustrated example, the front protrusion 212 extends continuously along the entire circumference of the outer peripheral surface of the front cover 210 in the X direction, as viewed from the front. In other words, the front protrusion 212 forms a recessed portion open to the front on the front of the front cover 210. However, the front protrusion 212 may be at least partially interrupted along the outer peripheral surface of the front cover 210 in the X direction, as viewed from the front.

[0039] The rear cover 220 covers the rear end of the battery element 100. The rear cover 220 is made of, for example, resin, metal, or the like. The rear end of the negative electrode tab 120 protrudes from the rear of the rear cover 220. Viewed from the rear, the rear cover 220 has a roughly rectangular shape with rounded corners in the X direction. Viewed from the rear, the long side of the rear cover 220 is roughly parallel to the Z direction, and the short side of the rear cover 220 is roughly parallel to the Y direction. The four corners of the rear cover 220 in the X direction are aligned with the four corners of the battery element 100 in the X direction.

[0040] like Figure 4 As shown, rear cover 220 has a rear protrusion 222. Rear protrusion 222 protrudes rearward of rear cover 220. As seen from the rear, rear protrusion 222, like front protrusion 212, at least partially surrounds a predetermined area behind rear cover 220 in the X direction. In this embodiment, negative electrode tab 120 is disposed in this predetermined area.

[0041] like Figure 1 as well as Figure 2 As shown, the winding portion 302 is in a generally cylindrical shape with openings to the front and rear. The front cover 210 is disposed inside the front opening of the winding portion 302. The rear cover 220 is disposed inside the rear opening of the winding portion 302. The winding portion 302 is wound around the battery element 100, the front cover 210, and the rear cover 220 in the X direction for one turn. Thus, as shown in FIG. Figure 4 As shown, the front cover 210, the rear cover 220, and the wrapping portion 302 form a storage space 500 for accommodating the battery element 100. The storage space 500 contains an electrolyte solution (not shown) along with the battery element 100. The manner in which the battery element 100 is wrapped in the wrapping portion 302 is not limited to the example described above.

[0042] The outer circumference of the front cover 210 in the X direction, including the outer circumference of the front protrusion 212 in the X direction, and the inner circumference of the front opening of the wrapping portion 302 in the X direction are joined together by heat welding. Thus, a front sealing portion 510 is formed in front of the storage space 500.

[0043] The outer circumference of the rear cover 220 in the X direction, including the outer circumference of the rear protrusion 222, and the inner circumference of the rear opening of the wrapping portion 302 in the X direction are joined together by heat welding. Thus, a rear seal portion 520 is formed at the rear of the accommodating space 500.

[0044] like Figure 1 as well as Figure 2 As shown, when viewed from the front, the lead portion 304 is led out from the upper left corner of the battery element 100 of the winding portion 302. Figure 2 As shown, the lead portion 304 includes a first lead portion 304a and a second lead portion 304b. The first lead portion 304a is led out from one of the two ends of the winding portion 302 in the circumferential direction around the X direction. The second lead portion 304b is led out from the other of the two ends of the winding portion 302 in the circumferential direction around the X direction. The first lead portion 304a and the second lead portion 304b are joined to each other by, for example, heat welding. Therefore, when viewed from the front, a side sealing portion 530 is formed on the upper side of the accommodating space 500. The lead portion 304 is bent along the upper surface of the battery element 100. However, the lead portion 304 does not have to be bent. In addition, the shape of the bend of the lead portion 304 is not limited to the shape involved in the embodiment.

[0045] In the embodiment, the outer circumferential surface of the front protrusion 212 in the X-direction and the inner circumferential surface of the front opening of the wrapping portion 302 in the X-direction are at least partially joined to each other by heat welding. For example, the entire outer circumferential surface of the front protrusion 212 in the X-direction and the entire inner circumferential surface of the front opening of the wrapping portion 302 in the X-direction are joined to each other by heat welding. During this heat welding, heat can be applied to the joined portion between the front protrusion 212 and the wrapping portion 302 from one side of at least one of the inner circumferential surface of the front protrusion 212 in the X-direction and the outer circumferential surface of the front opening of the wrapping portion 302 in the X-direction. As a result, the heat welding may at least partially form a fused portion between the outer circumferential surface of the front protrusion 212 in the X-direction and the inner circumferential surface of the front opening of the wrapping portion 302 in the X-direction. In one example, a fused portion of at least one of the front protrusion 212 and the wrapping portion 302 may be formed entirely between the outer circumferential surface of the front protrusion 212 in the X direction and the inner circumferential surface of the front opening of the wrapping portion 302 in the X direction. For example, heat can be applied to the junction between the front protrusion 212 and the wrapping portion 302 above the positive electrode tab 110 from the lower surface of the front protrusion 212 above the positive electrode tab 110 and the upper surface of the wrapping portion 302 above the positive electrode tab 110. Therefore, compared to simply applying heat to the upper surface of the wrapping portion 302 above the positive electrode tab 110 and the lower surface of the wrapping portion 302 below the positive electrode tab 110, heat can be more easily applied to the junction between the outer circumferential surface of the front protrusion 212 in the X direction and the inner circumferential surface of the front opening of the wrapping portion 302 in the X direction. Therefore, compared with the above-mentioned case, it is possible to easily increase the bonding strength between the front protrusion 212 and the wrapped portion 302. Therefore, compared with the above-mentioned case, it is possible to improve the sealing performance of the battery cell 10.

[0046] In the embodiment, the front protrusion 212 at least partially surrounds a predetermined area in front of the front cover 210 in the X-direction, as viewed from the front. Consequently, compared to a case where the front protrusion 212 is located only above, below, to the left, or to the right of the positive electrode tab 110, the bonding area between the outer circumference of the front protrusion 212 in the X-direction and the inner circumference of the opening in front of the wrapping portion 302 in the X-direction can be increased. Consequently, compared to the aforementioned case, the sealing performance of the battery cell 10 can be improved. Alternatively, the front protrusion 212 can be located only above, below, to the left, or to the right of the positive electrode tab 110.

[0047] In the embodiment, the outer circumferential surface of the front cover 210 in the X-direction and the outer circumferential surface of the front protrusion 212 in the X-direction are substantially flush. Therefore, compared to a case where there is a height difference between the outer circumferential surface of the front cover 210 in the X-direction and the outer circumferential surface of the front protrusion 212 in the X-direction, it is easier to join the wrapping portion 302 to both the outer circumferential surface of the front cover 210 in the X-direction and the outer circumferential surface of the front protrusion 212 in the X-direction. However, a height difference may also exist between the outer circumferential surface of the front cover 210 in the X-direction and the outer circumferential surface of the front protrusion 212 in the X-direction.

[0048] In the embodiment, the matters described regarding the connection between the outer circumferential surface of the front protrusion 212 in the X direction and the inner circumferential surface of the front opening of the wrapping portion 302 in the X direction also apply to the connection between the outer circumferential surface of the rear protrusion 222 in the X direction and the inner circumferential surface of the rear opening of the wrapping portion 302 in the X direction. Either the front protrusion 212 or the rear protrusion 222 may be omitted. For example, the front cover 210 may include the front protrusion 212, while the rear cover 220 may not include the rear protrusion 222.

[0049] Next, an example of a method for manufacturing the battery cell 10 according to the embodiment will be described. In this example, the battery cell 10 is manufactured as follows.

[0050] First, the battery element 100 is manufactured. The battery element 100 includes at least one positive electrode, at least one negative electrode, and at least one separator.

[0051] Next, the positive electrode tab 110 and the front cover 210 are joined together. Similarly, the negative electrode tab 120 and the rear cover 220 are joined together. Next, the positive electrode tab 110 and the positive electrode current collector 102a are joined together. Similarly, the negative electrode tab 120 and the negative electrode current collector 104a are joined together. Alternatively, the positive electrode tab 110 and the front cover 210 may be joined together after the positive electrode tab 110 and the positive electrode current collector 102a are joined together. Similarly, the negative electrode tab 120 and the rear cover 220 may be joined together after the negative electrode tab 120 and the negative electrode current collector 104a are joined together.

[0052] Next, the exterior film 300 is wrapped around the battery element 100 in the X direction once. This forms a wrapped portion 302. Furthermore, the excess length of the exterior film 300 is drawn out as a lead-out portion 304.

[0053] Next, the outer X-direction circumference of the front cover 210 and the inner X-direction circumference of the front opening of the wrapping portion 302 are joined together by heat fusion, including the outer X-direction circumference of the front protrusion 212. This forms the front seal 510. For example, the front protrusion 212 and the wrapping portion 302 are heat fused together using a sealing strip positioned in the area surrounded by the inner X-direction circumference of the front protrusion 212 and a sealing strip positioned outside the outer X-direction circumference of the front opening of the wrapping portion 302. In this example, heat can be applied from both the outer X-direction circumference of the front opening of the wrapping portion 302 and the inner X-direction circumference of the front protrusion 212. Specifically, heat can be applied from both the portion of the front opening of the wrapping portion 302 opposite the front protrusion 212 and the portion of the front protrusion 212 opposite the front opening of the wrapping portion 302. In this example, compared to a case where the front cover member 210 and the wrapped portion 302 are simply heat-welded together using a sealing strip disposed above the wrapped portion 302 above the positive electrode tab 110 and a sealing strip disposed below the wrapped portion 302 below the positive electrode tab 110, heat can be easily applied to the joint between the front cover member 210 and the wrapped portion 302. Therefore, compared to the above case, the joint strength between the front cover member 210 and the wrapped portion 302 can be improved.

[0054] Next, the outer X-direction circumference of the rear cover 220 and the inner X-direction circumference of the rear opening of the wrapping portion 302 are joined together by heat fusion, including the outer X-direction circumference of the rear protrusion 222. This forms the rear seal 520. For example, the rear protrusion 222 and the wrapping portion 302 are heat-fused together using a sealing strip positioned in the area surrounded by the inner X-direction circumference of the rear protrusion 222 and a sealing strip positioned outside the outer X-direction circumference of the rear opening of the wrapping portion 302. In this example, heat can be applied from both the outer X-direction circumference of the rear opening of the wrapping portion 302 and the inner X-direction circumference of the rear protrusion 222. Specifically, heat can be applied from both the portion of the rear opening of the wrapping portion 302 opposite the rear protrusion 222 and the portion of the rear protrusion 222 opposite the rear opening of the wrapping portion 302. In this example, compared to a case where the rear cover 220 and the wrapped portion 302 are simply thermally welded together using a sealing strip disposed above the wrapped portion 302 above the negative electrode tab 120 and a sealing strip disposed below the wrapped portion 302 below the negative electrode tab 120, heat can be easily applied to the joint between the rear cover 220 and the wrapped portion 302. Therefore, compared to the above case, the joint strength between the rear cover 220 and the wrapped portion 302 can be improved.

[0055] Next, electrolyte is injected into the storage space 500 through the gap between the first lead portion 304a and the second lead portion 304b. Next, the storage space 500 is evacuated through the gap between the first lead portion 304a and the second lead portion 304b. Next, the first lead portion 304a and the second lead portion 304b are joined by heat fusion to form the side seal portion 530. Thus, the storage space 500 is vacuum-sealed.

[0056] The method for vacuum-sealing the storage space 500 is not limited to the above example. In another example, first, the first lead portion 304a and the second lead portion 304b are joined by heat fusion to form the side seal 530. Next, the electrolyte is injected into the storage space 500 through an injection hole provided in at least one of the front cover 210 and the rear cover 220. The storage space 500 is then evacuated through the injection hole. The injection hole is then sealed with a predetermined cover.

[0057] Next, the side sealing portion 530 is bent along the upper surface of the battery element 100 .

[0058] In this manner, the battery cell 10 is manufactured.

[0059] As mentioned above, although embodiment of this invention was described with reference to drawings, these are illustrations of this invention, and various structures other than the above-mentioned can be adopted.

[0060] For example, in the embodiment, the positive electrode tab 110 and the negative electrode tab 120 are arranged on opposite sides of the battery element 100 in the X direction. However, both the positive electrode tab 110 and the negative electrode tab 120 may be arranged only on one of the front and rear sides of the battery element 100 in the X direction. In this case, the front and rear ends of the battery element 100 are covered by, for example, two cover members. Alternatively, only the side of the battery element 100 where the positive electrode tab 110 and the negative electrode tab 120 are extended may be covered by the cover member. In this example, the exterior film 300 may be sealed on the side of the battery element 100 opposite the cover member and folded along the battery element 100.

[0061] This application claims the benefit of priority based on Japanese patent application No. 2023-009501, filed on January 25, 2023, the disclosure of which is incorporated herein in its entirety.

[0062] Explanation of symbols

[0063] 10: Battery cell, 100: Battery element, 102: Positive electrode, 102a: Positive electrode collector, 104: Negative electrode, 104a: Negative electrode collector, 110: Positive electrode tab, 120: Negative electrode tab, 210: Front cover, 212: Front protrusion, 220: Rear cover, 222: Rear protrusion, 300: External film, 302: Wrapping portion, 304: Lead-out portion, 304a: First lead-out portion, 304b: Second lead-out portion, 500: Accommodation space, 510: Front sealing portion, 520: Rear sealing portion, 530: Side sealing portion.

Claims

1. A battery cell comprising: Battery elements; a cover member covering the ends of the battery element; and an outer film wrapped around the battery element and the cover, The cover member has a protrusion protruding toward the side of the cover member opposite to the battery element, The protrusion and the exterior film are at least partially joined to each other.

2. The battery cell according to claim 1, wherein: The protrusion at least partially surrounds a given area on an opposite side of the battery element relative to the cover member.

3. The battery cell according to claim 1 or 2, wherein: The fusion zone of at least one of the protrusion and the exterior film is at least partially present between the protrusion and the exterior film.

4. A method for manufacturing a battery cell, comprising: a step of wrapping an exterior film around a battery element and a cover member having a protrusion protruding toward the opposite side of the battery element and covering an end portion of the battery element; and and a step of at least partially bonding the protrusion and the exterior film to each other.

5. The method for manufacturing a battery cell according to claim 4, wherein: The step of at least partially bonding the protrusion and the exterior film to each other includes applying heat from a portion of the exterior film opposite to the protrusion and a portion of the protrusion opposite to the exterior film.

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