JP6970889B2 - Sealed battery - Google Patents

Description

The present invention relates to a sealed battery.

In recent years, lithium-ion batteries, nickel-metal hydride batteries and other secondary batteries have become increasingly important as power sources for vehicles, personal computers and mobile terminals. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a high output power source for mounting on a vehicle. In this type of secondary battery, a battery structure is known in which an electrode body is housed inside a battery case and an electrode terminal connected to the electrode body is pulled out to the upper end (cover body) of the battery case. For example, a sealed battery in which an electrode terminal is pulled out to a lid of a battery case and is caulked and fixed to the lid via a gasket is widely known. Patent Document 1 is disclosed as a prior art relating to this type of sealed battery.

Japanese Unexamined Patent Publication No. 2016-105355

Patent Document 1 is constructed by fastening the lid and the external terminal by caulking and deforming the caulking member (internal terminal) after being inserted into the through hole of the lid and the through hole of the external terminal. Sealed batteries are disclosed. According to this type of sealed battery, the caulked deformed portion of the caulking member and the contact portion between the external terminals serve as a conductive path between both terminals (that is, the caulking member and the external terminal).

Here, in order to further reduce the conduction resistance (electrical resistance) between the two terminals, the battery case, the external terminal, and the caulking member (internal terminal) are integrally assembled by caulking, and then the caulking member is deformed. Welding (for example, laser welding) may be performed to firmly join the portion where the portion and the external terminal are in contact with each other. By such welding, the conduction area between the two terminals (that is, the area of the portion where the conduction path is formed) increases, and thus low resistance between the two terminals can be realized.

However, in general, it has been difficult to improve the machining accuracy above a certain level by joining parts by welding due to their nature. Therefore, in order to stably realize low resistance between the caulking member (internal terminal) and the external terminal, it is necessary to increase the conduction area between both terminals by welding as much as possible.

In particular, such a problem tends to appear remarkably when welding and joining terminals on the negative electrode side, which often use copper as a material. The present invention has been made in view of this point, and the conduction state between the caulking member on the negative electrode side (negative electrode internal terminal) and the external terminal on the negative electrode side (negative electrode external terminal) is stable and excellent. It is an object of the present invention to provide a sealed battery to be obtained.

According to the present invention, an electrode body including a positive electrode and a negative electrode, a battery case accommodating the electrode body, internal terminals of the positive and negative electrodes electrically connected to the positive and negative electrodes inside the case, and the case. Provided is a sealed battery provided with an internal terminal of the positive and negative electrodes and an external terminal of the positive and negative electrodes electrically connected to the outside of the positive and negative electrodes.

The negative electrode external terminal has a plate portion formed in a direction along the outer wall of the case. Further, the negative electrode internal terminal has a pedestal portion located inside the case, and a shaft portion provided so as to project from the pedestal portion and penetrate the through hole of the case and the through hole of the plate portion. It is provided at the end of the shaft portion on the side opposite to the side on which the pedestal portion is located, and is formed by being crimped to a peripheral portion that protrudes outward from the through hole of the plate portion and surrounds the through hole of the plate portion. It has a crimped portion.

The radial peripheral edge of the crimped portion of the shaft portion is welded to the plate portion. Here, the welding, the following conditions: in the peripheral portion of the caulking portion, the side on which the plate portion of the caulking portion is located a distance h _a from the surface opposite to the plate portion, 0. It is performed on the caulked portion satisfying 1 mm or more and 0.55 mm or less;

According to such a configuration, the peripheral edge portion in the radial direction of the shaft portion of the crimped portion of the negative electrode internal terminal and the negative electrode external terminal can be suitably welded. This can increase the conductive area between the negative electrode internal terminal and the negative electrode external terminal. Such an increase in the conductive area can contribute to quality stabilization of the conductive state between both terminals realized by welding the negative electrode internal terminal and the negative electrode external terminal.

It is a figure which shows the cross section of the main part of the closed type battery which concerns on one Embodiment. It is an exploded view which shows typically each member before caulking processing which concerns on one Embodiment. It is sectional drawing for demonstrating the caulking processing of the negative electrode internal terminal which concerns on one Embodiment. It is a side view which enlarges and shows the peripheral part and the central part of the caulked part of the negative electrode internal terminal which concerns on one Embodiment. It is sectional drawing for demonstrating the welding process of the negative electrode internal terminal and the negative electrode external terminal which concerns on one Embodiment. It is a top view for demonstrating the welding process of the negative electrode internal terminal and the negative electrode external terminal which concerns on one Embodiment. FIG. 6 is a cross-sectional view taken along the line VII-VII'in FIG. It is a graph which shows the relationship between the edge height of a caulking part and the conduction area.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. In the following drawings, members / parts having the same function may be described with the same reference numerals, and duplicate explanations may be omitted or simplified. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relations.

Although not intended to be particularly limited, in the following, a wound electrode body (wound electrode body) and a non-aqueous liquid electrolyte (electrolyte solution) are housed in a flat square (box-shaped) case. The present invention will be described by taking as an example a sealed lithium ion secondary battery of the form.

FIG. 1 shows a cross section of a main part of the sealed battery 100 according to the present embodiment. As shown in FIG. 1, the sealed battery 100 includes a negative electrode internal terminal 10, a battery case 20, and a negative electrode external terminal 30. The negative electrode internal terminal 10 is electrically connected to the negative electrode of the electrode body inside the battery case 20. Further, the negative electrode external terminal 30 is provided on the outside of the battery case 20 and is electrically connected to the negative electrode internal terminal 10. The sealed battery 100 further includes a gasket 40 and an insulator 50. Here, the negative electrode internal terminal 10 in FIG. 1 shows a state after caulking, which will be described later.

<Battery case>
The battery case 20 includes a box-shaped (that is, a bottomed square cylinder) case body in which one of the narrow surfaces in a flat rectangular parallelepiped shape is an opening, and a lid that closes the opening. As the material constituting the battery case 20, the same material as that used in a general lithium ion secondary battery can be appropriately used. From the viewpoint of heat dissipation and the like, a battery case 20 in which almost the entire main body and lid are made of metal (for example, made of aluminum, stainless steel (SUS), steel, etc.) can be preferably adopted. On the upper surface (here, the lid) of the battery case 20, a negative electrode external terminal 30 that is electrically connected to the negative electrode of the wound electrode body via the negative electrode internal terminal 10 is arranged. Further, the battery case 20 is formed with a through hole 22 through which the shaft portion 12 of the negative electrode internal terminal 10, which will be described later, is inserted. In this embodiment, the lithium ion secondary battery 100 is a square battery, but the shape of the battery is not limited to the square shape and may be any shape such as a cylindrical shape.

<Negative electrode external terminal>
The negative electrode external terminal 30 is provided on the outside of the battery case 20. In the present embodiment, the negative electrode external terminal 30 has a plate portion 34 formed in a direction along the outer wall of the battery case 20 and a protrusion portion protruding from the plate portion 34 toward the outside of the battery case 20 (not shown). )have. The plate portion 34 is provided with a through hole 32 through which the shaft portion 12 of the negative electrode internal terminal 10 (undeformed negative electrode internal terminal 10a shown in FIG. 2) before caulking can be inserted. The through hole 32 is formed at a position corresponding to the through hole 22 of the battery case 20, and has an inner diameter large enough to fit the shaft portion 12 of the negative electrode internal terminal 10. As the constituent material of the negative electrode external terminal 30, a metal material such as aluminum can be preferably adopted.

<Insulator>
The insulator 50 is a member that insulates the negative electrode external terminal 30 and the battery case 20. The insulator 50 is arranged on an outer surface of the battery case 20 located outside the battery. The insulator 50 has a through hole 52 at a position corresponding to the through hole 22 of the battery case 20. The through hole 52 has an inner diameter large enough to fit the shaft portion 12 of the negative electrode internal terminal 10. The insulator 50 is compressed in the axial direction of the shaft portion 12 by caulking the negative electrode internal terminal 10 so that a portion surrounding the through hole 52 is sandwiched between the battery case 20 and the negative electrode external terminal 30. As a constituent material of the insulator 50, a resin material such as polyphenylene sulfide resin (PPS) or an aliphatic polyamide can be preferably adopted.

<Gasket>
The gasket 40 is provided with a through hole 42 through which the shaft portion 12 of the negative electrode internal terminal 10 (undeformed negative electrode internal terminal 10a shown in FIG. 2) before caulking is inserted. The gasket 40 is compressed by sandwiching a portion surrounding the through hole 42 between the battery case 20 and the pedestal portion 14 of the negative electrode internal terminal 10, so that the negative electrode internal terminal 10 (pedestal portion 14) and the battery case 20 are combined. And seal the through hole 22 of the battery case 20. The gasket 40 has a tubular portion 44 that is inserted into the through hole 22 of the battery case 20 from the inside and prevents (insulates) direct contact between the shaft portion 12 of the negative electrode internal terminal 10 and the battery case 20. The tubular portion 44 has a hollow cylindrical shape. The tubular portion 44 is provided so that its outer peripheral surface is in contact with the inner peripheral surface of the through hole 22 and its inner peripheral surface is in contact with the outer peripheral surface of the shaft portion 12 of the negative electrode internal terminal 10. As the constituent material of the gasket 40, various resin materials exhibiting resistance to the electrolytic solution to be used can be appropriately selected and used. For example, fluorinated resin such as perfluoroalkoxy alkane resin (PFA), polyphenylene sulfide resin (PPS), polyimide resin, polyamideimide resin, polyetheretherketone resin (PEEK), polyetherketoneketone resin (PEKK), polyethersulfone. A resin material such as resin (PES) can be adopted.

<Negative electrode internal terminal>
The negative electrode internal terminal 10 is made of a conductive material such as a metal material (copper or aluminum). The negative electrode internal terminal 10 is inserted through a through hole 22 provided in the battery case 20. The negative electrode internal terminal 10 is connected to the negative electrode external terminal 30 outside the battery case 20, and is electrically connected to the electrode body inside the battery case 20. The negative electrode internal terminal 10 electrically connects the negative electrode external terminal 30 and the electrode body.

FIG. 2 is an exploded view schematically showing each member before caulking, which will be described later. In the embodiment shown in FIGS. 1 and 2, the negative electrode internal terminal 10 (undeformed negative electrode internal terminal 10a) has a shaft portion 12 penetrating the battery case 20 and the negative electrode external terminal 30 and an outer peripheral surface of one end portion of the shaft portion 12. It has a pedestal portion 14 provided in the. The shaft portion 12 is inserted through the through hole 22 of the battery case 20 and extends through the battery case 20 in the axial direction. Further, the shaft portion 12 is further inserted into the through hole 52 of the insulator 50 and the through hole 32 of the negative electrode external terminal 30 outside the battery case 20, and penetrates the insulator 50 and the negative electrode external terminal 30 in the axial direction. The pedestal portion 14 is provided on the outer peripheral surface of one end portion of the shaft portion 12 in the battery case 20. The pedestal portion 14 has a collar shape extending in a direction orthogonal to the axial direction of the negative electrode internal terminal 10. In this embodiment, the pedestal portion 14 extends substantially parallel to the inner surface of the battery case (here, the lid body) 20 and is arranged between the battery case 20 and the electrode body.

<Caulking>
The negative electrode internal terminal 10 and the negative electrode external terminal 30 are fixed to the battery case 20 by caulking the negative electrode internal terminal 10 to the negative electrode external terminal 30 by caulking (riveting) processing. A caulking portion 16 is formed at the tip of the negative electrode internal terminal 10 (shaft portion 12) of FIG. 1 by caulking.

FIG. 3 is a cross-sectional view for explaining caulking of the negative electrode internal terminal 10 (undeformed negative electrode internal terminal 10a) according to the embodiment. In order to caulk the negative electrode internal terminal 10, first, the shaft portion 12 of the undeformed negative electrode internal terminal 10a, which is the negative electrode internal terminal 10 that has not yet been caulked, is subjected to the negative electrode external terminal 30, the insulator 50, and the battery. It is projected to the outside of the battery case 20 so as to penetrate the laminated portion in which the case 20 and the gasket 40 are laminated. Then, the end portion of the protruding undeformed negative electrode internal terminal 10 on the side opposite to the side where the pedestal portion 14 of the shaft portion 12 is located is radially used by a rotary caulking machine 60 having a rotating head 62. By caulking the peripheral portion surrounding the through hole 32 of the negative electrode external terminal 30, the crimped portion 16 is formed, the insulator 50 is compressed between the battery case 20 and the negative electrode external terminal 30, and the insulator 50 is compressed. The negative electrode external terminal 30, the battery case 20, the insulator 50, and the negative electrode internal terminal 10 are integrally fixed. Further, by the caulking process, the gasket 40 is compressed between the battery case 20 and the pedestal portion 14, thereby sealing the through hole 22 of the battery case 20.

FIG. 4 shows an enlarged peripheral portion 16a of the shaft portion 12 of the caulking portion 16 in the radial direction and a central portion 16b of the shaft portion 12 of the caulking portion 16 in the radial direction according to the embodiment formed by caulking. It is a side view which shows. Hereinafter, the “peripheral portion 16a of the caulking portion 16” refers to the peripheral edge portion 16a in the radial direction of the shaft portion 12 of the caulking portion 16. The shape of the caulked portion 16 will be briefly described with reference to FIG. 4.

In the peripheral portion 16a of the caulking portion 16, and the negative electrode external terminal 30 (plate portion 34) is the distance the edge height h _a of the surface opposite to the side where it is located to the plate portion 34 of the caulking portion 16. Further, the distance from the outermost position of the shaft portion 12 of the caulking portion 16 in the radial direction to the plate portion 34 is defined as the outermost peripheral height h _b . The length of the crimped portion 16 protruding outward in the radial direction of the shaft portion 12 from the position where the crimped portion 16 and the plate portion 34 of the negative electrode external terminal 30 are in close contact with each other is defined as an edge length d. Further, the distance from the position farthest from the plate portion 34 in the central portion 16b in the radial direction of the shaft portion 16 of the caulking portion 16 to plate portion 34, and crimping height h _c. Further, FIG. 6, which will be described later, shows the caulking diameter e, which is the diameter in the radial direction of the shaft portion 12 of the caulking portion 16.

Although described in detail later, from the viewpoint of conductivity improvement of the negative electrode internal terminal 10 and the negative electrode external terminal 30 by welding, caulking, the row so that the edge height h _a is 0.1mm or more 0.55mm or less It is preferable to be welded. The sizes of the outermost peripheral height h _b , the edge length d, the caulking height h _c, and the caulking diameter e are not particularly limited. Normally, by the caulking process described above, the caulking portion 16 has a shape that satisfies _{h b} <ha _a <h _{c, as shown in FIG.}

<Welding>
The negative electrode internal terminal 10 to which the caulking process is performed to form the caulked portion 16 is then welded to the plate portion 34 of the negative electrode external terminal 30. 5 and 6 are a cross-sectional view and a plan view for explaining the welding process between the negative electrode internal terminal 10 and the negative electrode external terminal 30 according to the embodiment, and FIG. 7 is a line VII-VII'in FIG. It is a cross-sectional view by. As shown in FIGS. 5, 6 and 7, the peripheral edge portion 16a of the caulked portion 16 is welded to the negative electrode external terminal 30. Preferably, continuous oscillation is performed with respect to the vicinity of the peripheral edge portion 16a of the caulking portion 16 (a region straddling from the peripheral edge portion 16a of the caulking portion 16 to the plate portion 34 located on the outside thereof (the radial outside of the shaft portion 16)). The laser beam La is irradiated, and the laser beam La moves so as to orbit along the outer edge of the caulking portion 16, so that welding (laser welding) is performed on the entire circumference of the caulking portion 16.

FIG. 7 shows an enlarged peripheral portion 16a of the caulked portion 16 after welding. A welded portion 70 is formed on the peripheral edge portion 16a of the caulked portion 16 by welding. As shown in FIG. 7, the length of the welded portion 70 in the boundary region between the negative electrode internal terminal 10 and the negative electrode external terminal 30 after welding is defined as the welded portion length f. After welding the caulked portion 16, the conduction area between the negative electrode internal terminal 10 and the negative electrode external terminal 30 can be calculated by measuring the welded portion length f. Such a conduction area can be an index of continuity between the negative electrode internal terminal 10 and the negative electrode external terminal 30.

Here, the present inventors control the shape of the crimped portion 16 of the negative electrode internal terminal 10 (particularly the shape of the peripheral portion of the crimped portion 16) to control the crimped portion 16 of the negative electrode internal terminal 10 and the negative electrode external terminal 30 (in particular, the shape of the peripheral portion of the crimped portion 16). It has been found that the conductive area between both terminals is increased by welding with the plate portion 34). According to the disclosed technique, edge height _{h a} of the caulking portion 16 is preferably not more than 0.55 mm. When the edge height h _a is not more than 0.55 mm, even if variation in the example the shape or size of the weld 70 formed by welding, stable during the negative internal terminal 10 and the negative electrode external terminal 30 It is possible to realize a conduction area large enough to realize low resistance. Further, it is preferable that the edge height _{h a} is 0.1mm or more. When the edge height h _a is too small than 0.1 mm, the influence of heat is likely to extend to peripheral components that may occur during the laser welding process.

As a method of controlling the edge height h _a of the caulking portion 16 is not particularly limited. As shown in FIG. 3, the bottom dead center of the rotary caulking machine 60 is controlled when the rotary caulking machine 60 having the rotary head 62 is used to perform caulking processing to caulk and deform the tip portion of the undeformed negative electrode internal terminal 10a. By doing so, it is possible to realize an _{edge height ha in a suitable range.} Specifically, as lowering the bottom dead center of the rotary swaging machine 60, the edge height h _a tends to decrease.

Hereinafter, test examples relating to the present invention will be described, but the following description is not intended to limit the present invention.

As shown in FIG. 2, a battery case (here, a lid) 20 was prepared, a gasket 40 was set on the inner side surface thereof, and an insulator 50 and a negative electrode external terminal 30 were set on the outer side surface. Next, the undeformed negative electrode internal terminal 10a before caulking is prepared, and the shaft portion 12 thereof is sequentially inserted into the through hole 22 of the battery case 20, the through hole 42 of the gasket 40, and the through hole 32 of the negative electrode external terminal 30. , Penetrated through the battery case 20 and the negative electrode external terminal 30. Then, by applying a load to the gasket 40 and the insulator 50 from the negative electrode external terminal 30 side and pressing the gasket 40 and the insulator 50, the tip portion of the shaft portion 12 of the undeformed negative electrode internal terminal 10a that has penetrated is formed. The end portion on the side opposite to the side on which the pedestal portion 14 is located is projected outward from the through hole 32 of the negative electrode external terminal 30. In that state, as shown in FIG. 3, using a rotary caulking machine 60 having a rotating head 62, the end portion of the protruding shaft portion 12 is radially enlarged in diameter to surround the through hole 32 of the negative electrode external terminal 30. By caulking the peripheral portion, the negative electrode external terminal 30 was attached to the through hole 22 of the battery case 20 (caulking) to construct an assembly.

In the caulking step, the setting of the bottom dead center of the rotary caulking machine 60 was changed up and down to perform caulking, and the shape of the caulking portion 16 formed after the caulking process was observed. Table 1 shows Example 1 in which the bottom dead center of the rotary caulking machine 60 is set relatively downward and caulking is performed, and the caulking process is performed by setting the bottom dead center of the rotary caulking machine 60 relatively upward. The result of observing the shape of the caulking portion 16 with respect to the performed Example 2 is shown.

As shown in Table 1, it was confirmed that the shape of the caulking portion 16 (particularly the edge height _ha ) can be controlled by controlling the bottom dead center of the rotary caulking machine 60. Result of performing a plurality of times such tests, as lowering the bottom dead center of the rotary swaging machine 60, the edge height h _a of the caulking portion 16 was confirmed to be prone to decrease.

Next, with respect to the caulked assembly, the peripheral edge portion 16a of the caulked portion 16 and the negative electrode external terminal 30 were joined all around by laser welding. The peripheral edge portion 16a of the caulked portion 16 after the welding process was observed, the welded portion length f (FIG. 7) was measured, and the conduction area was calculated from the welded portion length f. The results are shown in Table 1 and FIG. Incidentally, FIG. 8 is a graph showing the relationship between the edge height _h a [mm] and conduction area of the crimped portion 16 [mm ^2].

Table 1 and is apparent from the results shown in FIG. 8, as the edge height h _a of the caulking portion is small, the conduction area was improved. Here, when the conduction area is about 0.6 mm ² or more, low resistance between the negative electrode internal terminal 10 and the negative electrode external terminal 30 is stably achieved even if the welding quality varies in the welding process. It can be said that it can be done. Building from the results shown in Figure 8, the edge height h _a of the caulking portion 16 is less than 0.55 mm, the conduction area generally becomes 0.6 mm ² or more, a sealed battery having a practically suitable stable quality I found that I could do it.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above.

10 Negative electrode internal terminal 12 Shaft part 14 Pedestal part 16 Caulking part 20 Battery case 22 Through hole 30 Negative electrode external terminal 32 Through hole 34 Plate part 40 Gasket 42 Through hole 50 Insulator 52 Through hole 60 Rotary caulking machine 62 Rotating head 100 Sealed battery

Claims (1)

An electrode body having a positive electrode and a negative electrode,
A battery case for accommodating the electrode body and
Inside the case, the internal terminals of the positive and negative electrodes that are electrically connected to the positive and negative electrodes, respectively.
An external terminal of the positive and negative electrodes provided on the outside of the case and electrically connected to the internal terminal of the positive and negative electrodes, respectively.
It is a sealed battery equipped with
The negative electrode external terminal is
It has a plate portion formed in a direction along the outer wall of the case, and has a plate portion.
The negative electrode internal terminal is
Made of copper,
The pedestal located inside the case and
A shaft portion that protrudes from the pedestal portion and is provided so as to penetrate the through hole of the case and the through hole of the plate portion.
It is provided at the end of the shaft portion on the side opposite to the side on which the pedestal portion is located, and is formed by protruding outward from the through hole of the plate portion and being crimped to a peripheral portion surrounding the through hole of the plate portion. The caulking part and
Have,
At the radial peripheral edge of the crimped portion, the entire circumference of the crimped portion along the radial outer edge of the shaft portion is laser welded to the plate portion.
The welding is performed under the following conditions:
In the peripheral portion of the crimped portion, the distance ha from the surface of the crimped portion on the side opposite to the side on which the plate portion is located is 0.1 mm or more and 0.55 mm or less;
A sealed battery, characterized in that it is performed on the caulked portion that meets the requirements.

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