Secondary battery and manufacturing method thereof

Abstract

To solve a problem in which a conventional secondary battery has insufficient corrosion resistance in the poles.SOLUTION: A secondary battery according to the present invention includes an electrode body, a case for housing the electrode body, a current collecting portion 20 joined to a current collecting foil protruding from the electrode body, a lid 14 for the case, an electrode terminal 24 electrically connected to the current collecting portion 20, and a pole 20a having one end attached to the current collecting portion 20 inside the case and the other end provided with a crimped portion 28 located at a position passing through the lid 14 and the electrode terminal 24, and the pole 20a has a corrosion-resistant plating 20b material applied from the position where the material is housed in the case to the area where the material is rolled up into the crimped portion 28.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a secondary battery in which an electrode body inside a case is electrically connected to an electrode terminal outside the case by crimping a pole that penetrates from inside the case to outside the case, and to a method for manufacturing the secondary battery. [Background technology]

[0002] In non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, the electrode body inside the case is electrically connected to the electrode terminal outside the case by using a pole that penetrates from inside the case to outside the case. In this case, if corrosion progresses due to various factors in the members exposed to the outside of the case (e.g., the electrode terminals and the metal members connected to the electrode terminals), the resistance value increases, causing deterioration of the battery performance. Therefore, technologies for preventing corrosion of the electrode terminals are disclosed in Patent Documents 1 and 2.

[0003] The battery module described in Patent Document 1 is an energy storage device module in which a plurality of energy storage devices are arranged in parallel, each of which has a positive electrode terminal made of an aluminum-based metal material and a negative electrode terminal made of a copper-based metal material, and in which pole portions of the positive electrode terminal and the negative electrode terminal protrude from a wall portion of a case, and the positive electrode terminal and the negative electrode terminal of the different energy storage devices are connected by a conductive member, and the conductive member has a main body made of an aluminum-based metal material and has an insertion portion that penetrates the main body, and has a plating layer at least around the insertion portion on a surface of the main body and at a contact portion with the pole portion of the negative electrode terminal, and at least the negative electrode terminal has a threaded portion on the pole portion, and the pole portion of the positive electrode terminal and the conductive member are connected by welding, and the pole portion of the negative electrode terminal and the conductive member are connected by screwing a fastening member into the threaded portion.

[0004] The battery module described in Patent Document 1 is a storage module including a plurality of power storage devices and a connection member that electrically connects the plurality of power storage devices, wherein the power storage devices include an electrode assembly having a positive electrode, a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode, a case that houses the electrode assembly, a positive electrode terminal electrically connected to the positive electrode, and a negative electrode terminal electrically connected to the negative electrode, wherein the positive electrode terminal has a protrusion that protrudes to the outside of the case and a protective layer that covers at least a portion of an end face of the protrusion, wherein the protective layer is in contact with the connection member, the protrusion is made of pure aluminum, the protective layer is made of zinc or a zinc alloy, and a portion of the connection member that faces the end face of the protrusion is made of tin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-229564 A [Patent Document 2] JP 2015-125797 A Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques described in Patent Documents 1 and 2 prevent corrosion by plating parts that are prone to corrosion. However, when joining a terminal post to an electrode terminal by crimping the post, problems such as peeling of the plating occur because stress is generated in the post due to pressure and deformation during the crimping process. The techniques described in Patent Documents 1 and 2 are based on the premise of bolt fixation, and cannot be applied to parts where problems occur due to pressure and deformation during the crimping process.

[0007] The present invention has been made in consideration of the above circumstances, and aims to improve the corrosion resistance of a secondary battery in which an electrode body inside the case is electrically connected to an electrode terminal outside the case by crimping a pole that penetrates from inside the case to outside the case. [Means for solving the problem]

[0008] One aspect of the secondary battery of the present invention comprises an electrode body, a case that houses the electrode body, a current collecting component that is joined to a current collecting foil protruding from the electrode body, a lid for the case, an electrode terminal that is electrically connected to the current collecting component, and a pole having one end that is attached to the current collecting component within the case and a crimped portion at the other end that is provided at a position that penetrates the lid and the electrode terminal, and the pole has a corrosion-resistant plating material applied from the position that is housed within the case to the area that is rolled up into the crimped portion.

[0009] One aspect of a manufacturing method for a secondary battery according to the present invention includes a plating process in which a corrosion-resistant plating is performed on a pole, one end of which is attached to a current collecting component; a current collecting component attachment process in which a current collecting component is joined to a current collecting foil protruding from an electrode body; a terminal assembly process in which the current collecting component, the lid, and the electrode terminal are assembled so that the pole passes through through holes provided in the lid and the electrode terminal; a crimping process in which the other end of the pole is crimped after the terminal assembly process to form a crimped portion that is in close contact with the electrode terminal; a storage process in which the electrode body is stored in a case after the crimping process; and a sealing process in which the lid and the case are joined after the storage process, wherein in the plating process, before the pole is crimped in the crimping process, corrosion-resistant plating is applied to a surface area of ​​the pole including at least the range from the area exposed from the electrode terminal to one end of the pole. Effect of the Invention

[0010] According to the secondary battery and manufacturing method of the secondary battery of the present invention, it is possible to improve the corrosion resistance of a secondary battery in which an electrode body inside the case is electrically connected to an electrode terminal outside the case by crimping a pole that penetrates from inside the case to outside the case. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a secondary battery according to a first embodiment. [Diagram 2] FIG. 2 is a diagram for explaining components constituting a current collecting part and an electrode terminal according to the first embodiment. [Diagram 3] 4 is a flowchart illustrating a flow of a manufacturing process for the secondary battery according to the first embodiment. [Figure 4] 5A to 5C are diagrams for explaining in more detail a terminal assembly step and a crimping step according to the first embodiment. [Diagram 5] 10A to 10C are diagrams for explaining in more detail a terminal assembly step and a crimping step according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In order to clarify the description, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and repeated description is omitted as necessary. In the following description, the direction in which the longest side of the battery case extends is defined as the horizontal direction X or width direction X, the direction in which the shortest side of the case extends is defined as the thickness direction Z, and the direction perpendicular to the horizontal direction X and the thickness direction Z and which is the height of the case is defined as the height direction Y or vertical direction Y. In the following description, the horizontal direction X may be referred to as the left-right direction, and the vertical direction Y may be referred to as the up-down direction.

[0013] First embodiment First, a schematic diagram of a secondary battery 1 according to the first embodiment is shown in Fig. 1. As shown in Fig. 1, the secondary battery 1 according to the first embodiment has a case 10, an electrode body 11, and a lid 14. The electrode body 11 is stored in the case 10, and then the electrode body 11 is sealed in the case 10 by the lid 14.

[0014] The electrode body 11 is formed by laminating a positive electrode sheet and a negative electrode sheet with a separator sandwiched therebetween. This laminated structure can be formed as a laminated type in which a positive electrode sheet, a negative electrode sheet, and a separator are laminated, or as a wound type in which a long positive electrode sheet, a negative electrode sheet, and a separator are stacked and then wound. In the following explanation, an example in which a wound type electrode body is used as the electrode body 11 will be explained, but the present invention can also be applied to a laminated type electrode body.

[0015] The positive electrode sheet has a positive electrode composite layer coated with a positive electrode active material, and a positive electrode current collector tab 12 that is not coated with a positive electrode active material. The negative electrode sheet has a negative electrode composite layer coated with a negative electrode active material, and a negative electrode current collector tab 13 that is not coated with a negative electrode active material. In the electrode body 11, the positive electrode composite layer of the positive electrode sheet and the negative electrode composite layer of the negative electrode sheet are configured as a wound body so as to face each other, and the positive electrode current collector tab 12 protrudes from one end of the electrode body 11, and the negative electrode current collector tab 13 protrudes from the other end of the electrode body 11. In such a wound electrode body 11, when viewed in the thickness direction Z of the wound body, the positive electrode current collector tab 12 and the negative electrode current collector tab 13 are each in a state in which a plurality of current collector foils are overlapped. Therefore, in the secondary battery 1, the positive electrode current collector tab 12 is collected by a positive electrode current collector part 20. Moreover, on the negative current collector tab 13 side, the negative current collector tab 13 is collected by a negative current collector component 30. Here, the positive current collector tab 12 and the negative current collector component 30 are components mainly made of copper, and the negative current collector tab 13 and the negative current collector component 30 are components mainly made of aluminum.

[0016] As shown in FIG. 1, the secondary battery 1 according to the first embodiment has electrode terminals 24 and 34 on the upper surface of the lid 14. The electrode terminal 24 is electrically connected using a pole provided on the positive current collecting part 20. The electrode terminal 34 is electrically connected using a pole provided on the negative current collecting part 30. In this case, in the first embodiment, the pole is closed to electrically connect the pole and the electrode terminal. FIG. 1 shows a crimping part 28 that electrically connects the positive current collecting part 20 and the electrode terminal 24, and a crimping part 38 that electrically connects the negative current collecting part 30 and the electrode terminal 24. In the secondary battery 1 according to the first embodiment, a gasket is used to insulate the positive current collecting part 20 and the lid 14 and to maintain a sealed state inside the case. This gasket is provided between the positive current collecting part 20 and the lid 14. In the secondary battery 1 according to the first embodiment, a gasket is used to insulate the negative current collecting part 30 and the lid 14 and to maintain a sealed state inside the case. This gasket is provided between the negative current collecting part 30 and the lid 14. Furthermore, an insulator 22 is provided between the electrode terminal 24 and the lid 14, and an insulator 32 is provided between the electrode terminal 34 and the lid 14, thereby insulating the electrode terminal from the lid 14.

[0017] In the example shown in FIG. 1, the electrode bolt 26 is made to protrude from the electrode terminal 24, and the electrode bolt 36 is made to protrude from the electrode terminal 34. However, the presence or absence of electrode bolts depends on the product specifications, and the electrode post structure described in the first embodiment can be applied to any electrode terminal.

[0018] Here, the structure of the current collecting component and the electrode terminal in the secondary battery 1 according to the first embodiment will be described in more detail. Fig. 2 is a diagram for explaining the components constituting the current collecting component and the electrode terminal according to the first embodiment. Note that Fig. 2 shows the negative current collecting component 30 side in a completed state in which the negative current collecting component 30 and the electrode terminal 34 are assembled, as in Fig. 1, and shows the individual components on the positive current collecting component 20 side before the components are assembled. The components used for assembly and the assembly method are the same for the positive and negative sides, so only the positive side will be described below.

[0019] As shown in FIG. 2, the positive current collector 20 is provided with a pole 20a. More specifically, the pole 20a is attached to the positive current collector 20 in the case 10 of the secondary battery 1, one end of which is a finished product. A gasket 21 is sandwiched between the positive current collector 20 and the lid 14. An electrode terminal 24 is disposed on the outside of the lid 14 of the secondary battery 1 via an insulator 22. A through hole through which the pole 20a penetrates is provided in the gasket 21, the lid 14, the insulator 22, and the electrode terminal 24. When assembling the secondary battery 1, the gasket 21, the lid 14, the insulator 22, and the electrode terminal 24 are stacked so that the through holes are aligned, and the other end of the pole 20a is crimped with the pole 20a inserted into the through hole. As a result, a crimped portion 28 is formed at the other end of the pole 20a. That is, the pole post 20a has the other end penetrating the cover 14 and the electrode terminal 24, and a crimping portion 28 is provided at this other end.

[0020] The electrode bolt 26 is fitted into the insulator 22, and is provided so that the lid is pressed down by the electrode terminal 24. A hole for passing the electrode bolt 26 therethrough is provided in the electrode terminal 24, and the electrode bolt 26 is fixed so as to be inserted into this hole.

[0021] Next, a method for manufacturing the secondary battery 1 according to the first embodiment will be described. FIG. 3 shows a flowchart for explaining the flow of the manufacturing process of the secondary battery 1 according to the first embodiment. As shown in FIG. 3, in assembling the secondary battery 1 according to the first embodiment, first, a plating process is performed in which a corrosion-resistant plating is performed on the pole 20a, one end of which is attached to the current collecting component (step S1). More specifically, in the plating process, before the pole 20a is crimped in a crimping process described later, a corrosion-resistant plating is applied to an area of ​​the surface of the pole including at least the area from the area exposed from the electrode component to one end of the pole 20a. The area to which this plating is applied will be described in detail later.

[0022] The positive current collecting part 20 and the pole 20a are, for example, parts whose main component is copper. On the other hand, the cover 14 and the electrode terminal 24 are parts whose main component is aluminum. Here, the current collecting part and the pole whose main component is copper tend to be corroded by the electrolyte. The corrosion-resistant plating used to prevent galvanic corrosion needs to be a metal whose natural potential is lower (more base) than that of copper in the environment in which galvanic corrosion occurs. In this way, if a metal whose natural potential is lower than the material (e.g., copper) constituting the part is used as the corrosion-resistant plating, corrosion will progress more on the corrosion-resistant plating side than on the main body of the part, so that the main body of the part can be protected from corrosion. When the positive current collecting part 20 and the pole 20a are formed mainly of copper, any of zinc, aluminum, tin, iron, nickel, lead, and alloys containing these metals can be used as the corrosion-resistant plating.

[0023] Next, in the manufacturing process of the secondary battery 1 according to the first embodiment, a current collecting component attachment process is performed in which a current collecting component is joined to the current collecting foil protruding from the electrode body 11 (step S2). Specifically, in the current collecting component attachment process, a positive current collecting component 20 is joined to the positive current collecting tab 12, and a negative current collecting component 30 is joined to the negative current collecting tab 13.

[0024] Next, in the manufacturing process of the secondary battery 1 according to the first embodiment, a terminal assembling process is performed in which the current collecting part, the lid, and the electrode terminal are assembled so that the pole passes through the through holes provided in the lid and the electrode terminal (step S3). Specifically, in the terminal assembling process, the through holes provided in the gasket 21, the lid 14, the insulator 22, and the electrode terminal 24 are aligned, and then the pole 20a is passed through the through hole. In addition, the through holes provided in the gasket, the lid 14, the insulator 32, and the electrode terminal 34 are aligned, and then the pole of the negative current collecting part 30 is passed through the through hole.

[0025] Next, in the manufacturing process of the secondary battery 1 according to the first embodiment, a crimping process is performed in which the other end of the pole is crimped to form a crimped portion that is in close contact with the electrode terminal (step S4). Specifically, in the crimping process, the other end of the pole protruding from the electrode part in the assembly process is crimped by applying pressure, thereby forming the crimped portion 28 and the crimped portion 38.

[0026] Next, in the manufacturing process of the secondary battery 1 according to the first embodiment, the assembly process is completed through a storage process (step S5) in which the electrode body 11 is stored in the case 10, and a sealing process (step S6) in which the lid 14 and the case 10 are joined.

[0027] Here, one of the features of the secondary battery 1 according to the first embodiment is the range of the pole 20a to which the corrosion-resistant plating is applied in the plating process (step S1). This feature will be described in detail with reference to Fig. 4, which shows a more detailed explanation of the terminal assembly process (step S3) and the crimping process (step S4) according to the first embodiment.

[0028] 4, in the secondary battery 1 according to the first embodiment, a corrosion-resistant plating 20b is applied to a portion of the pole 20a, mainly on the case inner side. In the secondary battery 1 according to the first embodiment, a corrosion-resistant plating 20c is applied to the tip surface on the other end side of the pole 20a. In the secondary battery 1 according to the first embodiment, in the terminal assembling process (step S3), the gasket 21, the lid 14, the insulator 22 and the electrode terminal 24 are stacked, and then the positive electrode current collecting part 20 is inserted so as to penetrate through the through holes provided in each of the stacked members.

[0029] The state after this insertion step is completed is shown in the crimping step column of Fig. 4. Referring to the crimping step column of Fig. 4, it can be seen that the corrosion-resistant plating 20b applied to the terminal post 20a is applied to at least the area on the surface of the terminal post including the range from the area exposed from the electrode terminal 24 to one end of the terminal post 20a before the terminal post is crimped. The state after the crimping step is performed on the terminal post 20a with the corrosion-resistant plating 20b applied to such an area is shown in the "after crimping step is completed" column of Fig. 4.

[0030] The "After the crimping process is completed" section of Fig. 4 shows a side view of the vicinity of the electrode terminal 24 after the crimping process is completed, and a cross-sectional view of the electrode terminal 24 taken along a cross section passing through the center of the crimped portion. Referring to the "After the crimping process is completed" section of Fig. 4, by crimping the electrode post 20a, the corrosion-resistant plating 20b cannot be seen from the front, and the corrosion-resistant plating material is present from the position where it is stored in the case to the area that is rolled up into the crimped portion.

[0031] As described above, in the secondary battery 1 according to embodiment 1, by carrying out the crimping process in a state where the corrosion-resistant plating 20b is applied to the area extending from the portion of the pole 20a that becomes the inside of the case 10 to the portion that is crimped to become the curved portion, it becomes possible to bring the crimped portion 28 and the electrode terminal 24 into contact over a wide area without the contact area between the crimped portion 28 and the electrode terminal 24 being reduced by the corrosion-resistant plating 20b.

[0032] In addition, in the secondary battery 1 according to the first embodiment, the corrosion-resistant plating 20b is present on the bent portion by crimping, and the corrosion-resistant plating 20b exhibits a sacrificial anticorrosion function, improving the corrosion resistance of the pole 20a. In addition, in the secondary battery 1 according to the first embodiment, the corrosion-resistant plating 20b is present on the inside of the case 10 of the pole 20a, and therefore it is possible to prevent the progress of corrosion caused by the electrolyte in the case 10. In the verification by the inventors, the application of the corrosion-resistant plating 20b has an effect of reducing the contact resistance of the negative electrode by about 30% compared to the end of corrosion at the 200 msec resistance. Here, the 200 msec resistance is a value obtained by a test in which a rectangular pulse wave in which a constant current value and a constant time are changed between discharge and charge are passed through the measurement target and the resistance value for the first 200 msec period is read. In addition, the resistance value of the 200 msec resistance is calculated based on the results of multiple measurements.

[0033] Furthermore, in the secondary battery 1 according to the first embodiment, by wrapping the corrosion-resistant plating 20b around the corners (e.g., the portions that are bent by crimping) within the crimped portion 28 excluding the portions that come into contact with the electrode terminal 24, it becomes possible to reduce stress concentration while ensuring electrical continuity, and to improve fatigue strength.

[0034] Furthermore, in the secondary battery 1 according to the first embodiment, the corrosion resistance of the crimped portion is improved by providing the corrosion-resistant plating 20c on the other end of the corrosion-resistant plating 20b after crimping or on the surface of the crimped portion .

[0035] In addition, it is preferable to apply corrosion-resistant plating to both the positive and negative electrode sides. However, in the secondary battery 1, metals other than copper, which is the component on the positive electrode side, are used for the case, lid, electrode terminals, etc., and therefore applying corrosion-resistant plating to the same components on the positive electrode side is highly effective.

[0036] Embodiment 2 In the second embodiment, a corrosion-resistant plating 40b, which is another form of the corrosion-resistant plating 20b applied to the pole 20a, will be described. In the description of the second embodiment, the same components as those described in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

[0037] FIG. 5 is a diagram for explaining the terminal assembly process and the crimping process according to the second embodiment in more detail. In FIG. 5, the corrosion-resistant plating 20b described in FIG. 4 is replaced with the corrosion-resistant plating 40b. As shown in FIG. 5, the corrosion-resistant plating 40b is applied to the pole 20a so that a plurality of slits extending in the axial direction of the pole are provided. In addition, the portion of the corrosion-resistant plating 40b that protrudes beyond the electrode terminal 24 when the pole is inserted into the cover 14 is plated over the entire circumference of the pole without any slits. Even with the corrosion-resistant plating 40b with slits provided in this way, after the pole 20a is crimped, the corrosion-resistant plating 40b cannot be seen from the front, and the corrosion-resistant plating material is present from the position where the pole is housed in the case to the area that is rolled into the crimped portion, and the stress at the corners of the crimped portion is alleviated.

[0038] When pressure is applied to the electrode post 20a in the crimping process, the electrode post 20a expands and deforms. However, by using the corrosion-resistant plating 40b with slits, it is possible to prevent the corrosion-resistant plating from cracking or peeling off due to such expansion or deformation. The corrosion-resistant plating is a conductive member, and if it peels off and falls into the case 10, it may cause an unintended short circuit in the electrode body 11. In other words, by using the corrosion-resistant plating 40b, it is possible to prevent the generation of conductive dust inside the case 10 in the crimping process and improve the production yield.

[0039] Also, in the secondary battery according to the second embodiment, similarly to the secondary battery 1 according to the first embodiment, it is possible to obtain the effects of improving corrosion resistance and reducing stress concentration.

[0040] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0041] 1 Secondary battery 10 Cases 11 Electrode body 12 Positive electrode current collecting tab 13 Negative electrode current collecting tab 14 Lid 20 Positive current collector 20a pole pillar 20b, 20c, 40b Corrosion-resistant plating 21 Gasket 22, 32 Insulator 24, 34 electrode terminal 26, 36 Electrode Bolts 28, 38 Crimping part

Claims

1. An electrode body; A case for housing the electrode assembly; a current collecting part joined to a current collecting foil protruding from the electrode body; A lid of the case; an electrode terminal electrically connected to the current collecting component; a pole having one end attached to the current collecting part inside the case and the other end provided with a crimping portion provided at a position penetrating the cover and the electrode terminal, The electrode post has a corrosion-resistant plating material applied from the position where it is housed in the case to the area where it is rolled up into the crimped portion.

2. 2. The secondary battery according to claim 1, wherein the corrosion-resistant plating is applied to the electrode post so as to provide a plurality of slits extending in the axial direction of the electrode post.

3. The pole is made of copper as a main component, 2. The secondary battery according to claim 1, wherein the corrosion-resistant plating is a metal that is less noble than copper.

4. 4. The secondary battery according to claim 3, wherein the corrosion-resistant plating is any one of zinc, aluminum, tin, iron, nickel, lead, and alloys containing these metals.

5. The secondary battery according to claim 1 , wherein the surface of the crimped portion is coated with the corrosion-resistant plating.

6. a plating process for performing a corrosion-resistant plating process on a pole, one end of which is attached to a current collecting part; a current collecting part attachment step of joining a current collecting part to a current collecting foil provided so as to protrude from the electrode body; a terminal assembling process of assembling the current collecting part, the lid, and the electrode terminal so that the pole passes through a through hole provided in the lid and the electrode terminal; a crimping process for crimping the other end of the pole after the terminal assembling process to form a crimped portion that is in close contact with the electrode terminal; a housing step of housing the electrode body in a case after the crimping step; A sealing process of joining the lid and the case after the storing process, In the plating process, a corrosion-resistant plating is applied to a surface area of ​​the pole including at least the range from the area exposed from the electrode terminal to one end of the pole before the pole is crimped in the crimping process.

7. 7. The method for producing a secondary battery according to claim 6, wherein in the plating step, the corrosion-resistant plating is applied to the electrode post so as to provide a plurality of slits extending in an axial direction of the electrode post.

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