Can sealing lid, secondary battery, and method for manufacturing a secondary battery

Abstract

To solve a problem of a conventional bonding surface structure in which a process becomes complicated due to the formation and management of grooves or protrusions.SOLUTION: A sealing can lid 11 applied to a secondary battery case 10 includes a base plate that becomes a main body of the sealing can lid 11, and a hole 30 provided in the base plate into which a cap 15 is inserted, and the hole 30 has a tapered surface 20 whose side surface is tapered such that the diameter of the hole decreases toward the inside of the case 10 when viewed in cross section.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to, for example, a sealing lid of a secondary battery used as a vehicle battery, a secondary battery, and a method for manufacturing a secondary battery.

Background Art

[0002] In the assembly process of a secondary battery, the case in which the power body is housed is sealed by joining the case and various lids. One of these joining methods is ultrasonic joining. Therefore, a technique related to a surface joining structure of a battery suitable for ultrasonic joining is disclosed in Patent Document 1.

[0003] The battery joining surface structure described in Patent Document 1 has a base member which is one of the metal members for the battery to be joined, and a joined member which is the other of the metal members for the battery to be joined, and at least one of the base member and the joined member has a groove formed in the joining surface where the base member and the joined member contact each other. In a state where the base member and the joined member are joined, at least 70% or more of the groove has disappeared compared to before joining. Further, in the joining surface structure described in Patent Document 1, it has an energy director provided so as to protrude from the flat surface of the member on the joining surface, and this energy director constitutes one or more grooves.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the surface joint structure described in Patent Document 1 requires the formation of grooves or protrusions on the joint surface, and these grooves or protrusions must be formed and controlled. In other words, the technology disclosed in Patent Document 1 has the problem of complicating the process due to the formation and control of grooves or protrusions.

[0006] This invention has been made in view of the above circumstances, and aims to provide a sealing lid that enables efficient ultrasonic bonding while facilitating process control, and a secondary battery having said sealing lid. [Means for solving the problem]

[0007] One embodiment of the sealing lid of the present invention is a sealing lid applied to the case of a secondary battery, comprising a base plate which forms the body of the sealing lid, and a hole provided in the base plate into which a cap is fitted, wherein the hole has a tapered surface in cross-sectional view, with the diameter of the hole decreasing toward the inside of the case.

[0008] One embodiment of the secondary battery of the present invention comprises a case in which a power element is enclosed, and a sealing lid that seals the case, wherein the sealing lid is provided on a base plate which is the body of the sealing lid and has a hole into which a cap is fitted, and the hole has a tapered surface in cross-sectional view such that the diameter of the hole decreases toward the inside of the case.

[0009] One embodiment of the present invention relates to a method for manufacturing a secondary battery, comprising: a power element insertion step of inserting a power element into a case; a sealing step of joining a sealing lid to the opening of the case into which the power element is inserted; an electrolyte injection step of pouring an electrolyte into the case through a hole provided in the sealing lid into which a cap is fitted; and a sealing step of joining the cap and the sealing lid with the cap fitted into the hole, wherein in the sealing step, the outer circumference of the cap is in contact with a tapered surface formed on the side surface of the hole, which has a tapered shape in cross-sectional view such that the diameter of the hole decreases toward the inside of the case, and the cap and the sealing lid are joined by ultrasonic bonding.

[0010] In the sealing lid, secondary battery, and method for manufacturing a secondary battery of the present invention, a hole is provided in the sealing lid having a tapered side surface in which the diameter of the hole decreases toward the inside of the case. Furthermore, in the sealing lid, secondary battery, and method for manufacturing a secondary battery of the present invention, the edge of the cap is supported by this tapered side surface, and the contact portion between the tapered surface and the edge of the cap is ultrasonically bonded. [Effects of the Invention]

[0011] According to the sealing lid, secondary battery, and method for manufacturing the secondary battery of the present invention, it is possible to provide a sealing lid that enables efficient ultrasonic bonding while facilitating process control, and a secondary battery having the sealing lid. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view illustrating the structure of a secondary battery according to Embodiment 1. [Figure 2] This is a cross-sectional view illustrating the structure of the joint portion of the sealing lid according to Embodiment 1. [Figure 3] This is a free chart illustrating the manufacturing method of a secondary battery according to Embodiment 1. [Figure 4] This is a cross-sectional view illustrating in detail the sealing process of the secondary battery according to Embodiment 1. [Figure 5] This is a cross-sectional view illustrating the structure of the joint portion of a first example of a sealing lid according to Embodiment 2. [Figure 6] This is a cross-sectional view illustrating the structure of the joint portion of a second example of a sealing lid according to Embodiment 2. [Modes for carrying out the invention]

[0013] Embodiment 1 Embodiments of the present invention will be described below with reference to the drawings. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary.

[0014] First, the junction structure according to Embodiment 1 can be used for both primary batteries that cannot be charged or discharged, and secondary batteries that can be charged or discharged. However, the following description will focus on the junction structure used in secondary batteries. Figure 1 shows a perspective view illustrating the structure of secondary battery 1 according to Embodiment 1.

[0015] As shown in Figure 1, the secondary battery 1 according to Embodiment 1 has a case 10 and a sealing lid 11. The power element is housed in the case 10. The sealing lid 11 seals the case 10 with the power element housed inside. The sealing lid 11 is provided with a positive electrode 12 and a negative electrode 13. The positive electrode 12 is an electrode that extracts power from the positive electrode of the power element inside the case 10, and is joined to a positive electrode column and a positive electrode rivet 12a that penetrates the sealing lid 11. The positive electrode column, positive electrode rivet 12a, and positive electrode 12 are joined by laser welding. The negative electrode 13 is an electrode that extracts power from the negative electrode of the power element inside the case 10, and is joined to a negative electrode column and a negative electrode rivet 13a that penetrates the sealing lid 11. The negative electrode column, negative electrode rivet 13a, and negative electrode 13 are joined by laser welding.

[0016] Furthermore, the sealing lid 11 is provided with a release valve 14 and a cap (for example, an injection hole cap 15). The injection hole cap 15 is a cap that is joined to the sealing lid 11 by ultrasonic bonding. The release valve 14 is a valve that reduces the internal pressure of the sealed case 10 when the internal pressure inside the case 10 exceeds a certain level. The injection hole cap 15 is a cap for a hole (for example, an injection hole) through which electrolyte is injected into the case 10.

[0017] In the following description, the joint structure provided on the sealing lid 11 according to Embodiment 1 will be explained using the joint structure provided on the liquid injection hole cap 15 as an example. Therefore, Figure 2 shows a cross-sectional view illustrating the structure of the joint portion of the sealing lid 11 according to Embodiment 1. The cross-sectional view shown in Figure 2 is a cross-sectional view of the sealing lid 11 along the cross-sectional line that crosses the liquid injection hole cap 15.

[0018] As shown in FIG. 2, the can lid 11 includes a base plate that forms the main body of the can lid 11, and a liquid injection hole 30 that is provided in the base plate and serves as a hole into which the liquid injection hole cap 15 is inserted. In the can lid 11 according to the first embodiment, the side wall of the liquid injection hole 30 has a tapered surface 20 that is tapered such that the diameter of the hole decreases toward the inside of the case 10 in a cross-sectional view.

[0019] Also, in the example shown in FIG. 2, the side wall of the liquid injection hole 30 has a horizontal receiving portion 21 and a vertical guide portion 22. The horizontal receiving portion 21 is provided near the inner end of the side wall of the liquid injection hole 30 inside the case 10 and is continuous with the inner end of the tapered surface 20 inside the case 10. The horizontal receiving portion 21 is a protrusion that prevents the liquid injection hole cap 15 from falling into the case 10. The vertical guide portion 22 is a vertical surface that connects the upper surface of the can lid 11 and the tapered surface 20 provided on the side wall of the liquid injection hole 30.

[0020] Also, FIG. 2 shows the structure of the liquid injection hole cap 15. In the example shown in FIG. 2, an enlarged view of the edge portion 151 of the liquid injection hole cap 15 is also shown. The liquid injection hole cap 15 applied to the can lid 11 according to the first embodiment may have a burr 31 on the edge portion 151. This is because, by using the can lid 11, the edge portion 151 of the liquid injection hole cap 15 filled in the liquid injection hole 30 is pressed against the tapered surface 20 and functions as an energy director that improves the transmission efficiency of ultrasonic vibration. Even if there is no burr 31 on the edge portion 151 of the liquid injection hole cap 15, the edge portion 151 has an angle close to a right angle, so this edge portion 151 functions as an energy director. And, although it will be described in detail later, in the secondary battery 1 according to the first embodiment, the can lid 11 and the liquid injection hole cap 15 joined by ultrasonic waves are in a state where the edge portion 151 of the liquid injection hole cap 15 is embedded in the tapered surface 20.

[0021] Next, the manufacturing method of the secondary battery 1 according to Embodiment 1 will be described. Figure 3 shows a free chart illustrating the manufacturing method of the secondary battery 1 according to Embodiment 1. The flowchart shown in Figure 3 shows the assembly process of the secondary battery among the manufacturing processes of the secondary battery. As shown in Figure 3, in the assembly of the secondary battery 1 according to Embodiment 1, first, a power element insertion process is performed in which a power element is inserted into the case 10 (step S1). Next, a sealing process is performed in which a sealing lid 11 is joined to the opening of the case 10 into which the power element has been inserted (step S2). In this step 2, the case 10 and the sealing lid 11 are joined by laser welding. After that, an electrolyte injection process is performed in which electrolyte is injected into the case 10 through a hole (for example, an electrolyte injection hole 30) provided in the sealing lid 11 into which a cap 15 is fitted (step S3). Next, the assembly of the secondary battery 1 is completed by performing a sealing process in which the electrolyte injection hole cap 15 and the sealing lid 11 are joined with the electrolyte injection hole cap 15 fitted into the electrolyte injection hole 30 (step S4).

[0022] In the sealing step S4, the outer circumference of the liquid injection hole cap 15 is in contact with a tapered surface 20 formed on the side of the liquid injection hole 30, which has a tapered shape in which the diameter of the hole decreases toward the inside of the case 10 in a cross-sectional view, and the liquid injection hole cap 15 and the sealing lid 11 are joined by ultrasonic bonding. The details of the sealing step will now be explained in more detail with reference to Figure 4. Figure 4 is a cross-sectional view illustrating in detail the sealing step of the secondary battery according to Embodiment 1.

[0023] Figure 4 shows the state in step S4-1, where the liquid injection hole cap 15 is fitted into the liquid injection hole 30. In step S4-1, the edge portion 151 of the liquid injection hole cap 15 is in contact with the tapered surface 20 inside the liquid injection hole 30. In this state, by pressing the bonding tip 40 against the liquid injection hole cap 15, the liquid injection hole cap 15 and the sealing lid 11 are ultrasonically bonded.

[0024] In Figure 4, step S4-2 shows the state in which the sealing lid 11 and the liquid filling hole cap 15 are ultrasonically bonded. As shown in step S4-2, when the sealing lid 11 and the liquid filling hole cap 15 are ultrasonically bonded, the edge portion 151 of the liquid filling hole cap 15 is embedded in the tapered surface 20 of the sealing lid 11. This is because the material of the liquid filling hole cap 15 is harder than the material of the sealing lid 11. In the secondary battery 1 according to Embodiment 1, a bonding surface 32 is formed on two sides of the liquid filling hole cap 15: a part of the side wall of the liquid filling hole cap 15 (especially around the end on the inside of the case 10) and a part of the bottom surface of the liquid filling hole cap 15 (especially around the end on the side wall side of the liquid filling hole 30).

[0025] As described above, in the secondary battery 1 according to Embodiment 1, a tapered surface 20 is formed on the side wall of the liquid injection hole 30 into which the liquid injection hole cap 15 is fitted, and ultrasonic bonding is performed by pressing the edge portion 151 of the liquid injection hole cap 15 against the tapered surface 20. As a result, in the secondary battery 1, highly efficient ultrasonic bonding is possible with the edge portion 151 of the liquid injection hole cap 15 acting as an energy director.

[0026] Furthermore, in the combination of the sealing lid 11 and the liquid injection hole cap 15 according to Embodiment 1, there is no need to form grooves or protrusions on the joint surface, and it is not a problem even if there are burrs 31 on the edge portion 151 of the liquid injection hole cap 15. Therefore, by using the sealing lid 11 according to Embodiment 1, the process can be simplified by omitting the deburring process and burr inspection process of the sealing lid 11, thereby suppressing both management costs and manufacturing costs. Moreover, the tapered surface 20 of the sealing lid 11 can be formed by general pressing or cutting processes alone, and the accuracy error can be easily managed, so there is almost no increase in manufacturing costs or process control.

[0027] Furthermore, in the combination of the sealing lid 11 and the liquid injection hole cap 15 according to Embodiment 1, the joint surface is formed over two sides: a part of the side wall of the liquid injection hole cap 15 (especially around the end on the inside of the case 10) and a part of the bottom surface of the liquid injection hole cap 15 (especially around the end on the side wall side of the liquid injection hole 30). This allows for high joint strength to be achieved.

[0028] Embodiment 2 Embodiment 2 describes sealing lids 11a and 11b, which are different forms of the sealing lid 11. In the description of Embodiment 2, the same reference numerals as in Embodiment 1 are used for components that are the same as in Embodiment 1, and their descriptions are omitted.

[0029] First, Figure 5 shows a cross-sectional view illustrating the structure of the joint portion of a first example of a sealing lid according to Embodiment 2. In the following description, this first example will be referred to as the sealing lid 11a. As shown in Figure 5, the sealing lid 11a has a recess in the tapered surface 20 for positioning the liquid injection hole cap 15. More specifically, the recess 23 is formed by creating a step in the tapered surface 20. Due to this recess 23, the relative inclination of the liquid injection hole cap 15 with respect to the sealing lid 11a becomes horizontal, thus enabling better ultrasonic bonding than in Embodiment 1. In addition, in the sealing lid 11a, the edge portion 151 of the liquid injection hole cap 15 is in contact with the tapered surface 20, so the edge portion 151 can effectively function as an energy director.

[0030] Next, Figure 6 shows a cross-sectional view illustrating the structure of the joint portion of a second example of the sealing lid according to Embodiment 2. In the following description, this second example will be referred to as sealing lid 11b. As shown in Figure 6, sealing lid 11b has a protrusion on the tapered surface 20 for positioning the liquid injection hole cap 15. More specifically, the protrusion 24 is formed to protrude from the tapered surface 20. Due to this protrusion 24, the relative inclination of the liquid injection hole cap 15 with respect to the sealing lid 11a becomes horizontal, thus enabling better ultrasonic bonding than in Embodiment 1. In addition, in sealing lid 11b, the edge portion 151 of the liquid injection hole cap 15 is in contact with the tapered surface 20, so the edge portion 151 can effectively function as an energy director.

[0031] As described above, by providing the recess 23 or protrusion 24 for positioning as described in Embodiment 2, the inclination of the liquid injection hole cap 15 with respect to the tapered surface 20 can be easily controlled.

[0032] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0033] 1 Secondary battery 10 cases 11. Can sealing lid 12 Positive electrode 12a Positive rivet 13 Negative electrode 13a Negative electrode rivet 14. Opening valve 15. Injection port cap 151 Edge section 20 Tapered surface 21 Horizontal support section 22 Vertical guide section 23 Recess 24 Convex part 30 Liquid injection hole 31 Bali 32 Joint surface 40 bonding tips

Claims

1. A sealing lid applicable to the case of a secondary battery, The base plate which forms the main body of the sealing lid, The hole provided in the base plate, It has a cap that fits into the aforementioned hole, The hole has a tapered surface in cross-sectional view, where the side surface has a tapered shape in which the diameter of the hole decreases toward the inside of the case. The cap is a sealing lid in which a joining surface is formed on two sides, a part of the side wall of the cap and a part of the bottom surface of the cap, in a state in which the cap is embedded in the tapered surface on the side, and the tapered surface and the cap are joined together.

2. The sealing lid according to claim 1, wherein the hole is provided with a recess or protrusion on the tapered surface for positioning the cap.

3. Cases in which the power source is enclosed, The case has a sealing lid that seals the case, The aforementioned sealing lid is The base plate which forms the main body of the sealing lid, The hole provided in the base plate, It has a cap that fits into the aforementioned hole, The hole has a tapered surface in cross-sectional view, where the side surface has a tapered shape in which the diameter of the hole decreases toward the inside of the case. The cap is embedded in the tapered side surface of the secondary battery, and a joining surface is formed on two sides of the cap, a part of the side wall and a part of the bottom surface, to join the tapered surface and the cap.

4. A method for manufacturing a secondary battery, A power element insertion process in which a power element is inserted into the case, A sealing step of joining a sealing lid to the opening of the case into which the power unit is inserted, The process includes pouring electrolyte into the case through a hole provided in the sealing lid into which the cap is fitted, The process includes a sealing step of joining the cap and the can lid with the cap fitted into the hole, A method for manufacturing a secondary battery, comprising: in the sealing step, joining the cap and the sealing lid by ultrasonic bonding with the outer circumference of the cap in contact with a tapered surface formed on the side of the hole, which has a tapered shape in which the diameter of the hole decreases toward the inside of the case when viewed in cross-section, thereby forming a bonding surface on two sides, a part of the side wall of the cap and a part of the bottom surface of the cap, where the tapered surface and the cap are joined.

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