Cylindrical battery and method for manufacturing cylindrical battery

Abstract

To realize a cylindrical battery having excellent welding strength between an outer can and a sealing body.SOLUTION: A cylindrical battery 1 includes an outer can 10, a sealing body 60, and a welded portion 100. The outer can 10 has a bottomed cylindrical shape with one end side opened and accommodates a battery element of the cylindrical battery 1. The sealing body 60 seals the one end side of the outer can 10. The welded portion 100 welds the outer can 10 and the sealing body 60 and extends in a direction T along a boundary Q between them. In the cylindrical battery 1, a value obtained by dividing a maximum welding depth D from an outermost surface of the welded portion 100 in the direction T by a larger one of a thickness B1 of the outer can 10 and a thickness B2 of the sealing body 60 is 0.4 or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cylindrical battery and a method for manufacturing a cylindrical battery. [Background technology]

[0002] Known technologies include a technique for sealing the opening of a cylindrical outer can that houses a positive electrode, a negative electrode, etc., with a sealing plate, and a technique for joining the outer periphery of a sealing plate shaped to fit the opening of the outer can to the inner wall of the opening of the outer can by laser welding (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-122842 Summary of the Invention [Problem to be solved by the invention]

[0004] In a cylindrical battery in which an outer can housing a battery element is sealed with a sealing body, the outer can and the sealing body are welded together using a technique such as laser welding. However, in a cylindrical battery, if abnormal heat is generated due to an internal short circuit in the battery element or physical impact, the internal pressure inside the outer can sealed with the sealing body may increase. In a cylindrical battery, if the welding strength between the outer can and the sealing body is insufficient, the welded portion may not be able to withstand the internal pressure when the internal pressure increases, which could result in the cylindrical battery exploding.

[0005] In one aspect, the present invention aims to provide a cylindrical battery having excellent welding strength between the outer can and the sealing member. [Means for solving the problem]

[0006] In one aspect, there is provided a cylindrical battery including: a battery element; a bottomed cylindrical outer can having one end open and accommodating the battery element; a sealing body sealing the one end of the outer can; and a welded portion welding the outer can and the sealing body together and extending in a first direction along the boundary between the outer can and the sealing body, wherein the value obtained by dividing the maximum weld depth from the outermost surface of the welded portion in the first direction by the maximum thickness of the outer can and the sealing body is 0.4 or greater.

[0007] In another aspect, there is provided a method for manufacturing a cylindrical battery as described above. [Effects of the Invention]

[0008] In one aspect, it is possible to realize a cylindrical battery with excellent welding strength between the outer can and the sealing member. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a cylindrical battery. [Figure 2] 10A and 10B are diagrams illustrating an example of a welded outer can and sealing body. DETAILED DESCRIPTION OF THE INVENTION

[0010] Fig. 1 is a diagram illustrating an example of a cylindrical battery, which schematically shows a cross-sectional view of a main part of an example of a cylindrical battery. As an example, a cylindrical battery 1 shown in FIG. 1 includes an outer can 10, a battery element 20, an electrolyte 30, an insulating plate 40, an insulating plate 50, a sealing body 60, a gasket 70, a positive electrode terminal 80, and a washer 90.

[0011] The cylindrical battery 1 may be a primary battery such as a lithium battery, or a secondary battery such as a lithium ion battery. The outer can 10 is a cylindrical, conductive container with a bottom and an open end 11. The outer can 10 is made of a material such as steel, nickel-plated steel, or stainless steel.

[0012] The battery element 20 is an example of a power generating element housed in the exterior can 10. Fig. 1 shows, as an example, the battery element 20 having a configuration including a sheet-shaped positive electrode 21, a sheet-shaped negative electrode 22, and a sheet-shaped separator 23. The battery element 20 has a so-called spiral electrode structure in which the positive electrode 21 and the negative electrode 22 are spirally wound with the separator 23 interposed therebetween.

[0013] The positive electrode 21 of the battery element 20 uses a positive electrode material containing a positive electrode active material. For example, if the cylindrical battery 1 is a lithium battery, manganese dioxide or the like is used as the positive electrode active material. For example, if the cylindrical battery 1 is a lithium ion battery, lithium cobalt oxide or the like is used as the positive electrode active material. The positive electrode 21 may be formed by laminating a positive electrode material on a stainless steel expanded metal or the like that functions as a current collector. A conductive positive electrode tab 21a is connected to the positive electrode 21.

[0014] The negative electrode 22 of the battery element 20 uses a negative electrode material containing a negative electrode active material. For example, when the cylindrical battery 1 is a lithium battery or a lithium ion battery, lithium or the like is used as the negative electrode active material. Examples of negative electrode materials containing a negative electrode active material include metallic lithium and lithium alloys such as lithium-aluminum alloys. The negative electrode 22 may be formed by laminating a negative electrode material on copper foil or the like that functions as a current collector. A conductive negative electrode tab 22a is connected to the negative electrode 22.

[0015] The positive electrode 21 and the negative electrode 22 are wound together with a separator 23 interposed therebetween. The separator 23 may be made of a polyolefin or cellulose porous film, a woven fabric, a nonwoven fabric, or the like. A non-aqueous organic electrolyte solution in which a lithium electrolyte salt is dissolved in an organic solvent is used as the electrolyte solution 30 of the cylindrical battery 1. Examples of the lithium electrolyte salt include lithium trifluoromethanesulfonate. Examples of the organic solvent include ethylene carbonate, propylene carbonate, and 1,2-dimethoxyethane.

[0016] Inside the exterior can 10, for example, an insulating plate 40 and an insulating plate 50 are provided on the bottom and the top of the battery element 20 housed therein, respectively. The sealing body 60 has, for example, a disk-shaped or annular bottom plate portion 61 having an opening 61a in the center, and a side wall portion 62 rising from the outer periphery of the bottom plate portion 61. An insulating material such as resin is used for the gasket 70. A conductive material such as metal is used for the positive terminal 80 and the washer 90. The positive terminal 80 and the washer 90 are fixed to the opening 61a provided in the bottom plate portion 61 of the sealing body 60 via the gasket 70.

[0017] A positive electrode tab 21a connected to the positive electrode 21 of the battery element 20 is connected to a positive electrode terminal 80 fixed to the sealing body 60 via a gasket 70 together with a washer 90. A negative electrode tab 22a connected to the negative electrode 22 of the battery element 20 is connected to the inner wall of the outer can 10. The outer can 10 (for example, a part of its bottom surface) functions as a negative electrode terminal.

[0018] The sealing body 60 is fitted into the open end 11 of the outer can 10. The side wall portion 62 of the sealing body 60 is further welded to the open end 11 of the outer can 10. The outer can 10 and the sealing body 60 are mechanically connected and fixed to each other by a welded portion 100 formed by welding. As a result, the outer can 10 containing the battery element 20 together with the electrolyte 30 is sealed and airtight by the sealing body 60 to which the positive electrode terminal 80 and the washer 90 are fixed via the gasket 70.

[0019] The cylindrical battery 1 having the above-described configuration is manufactured, for example, using the following method. First, a bottomed cylindrical outer can 10, a sheet-like positive electrode 21, a sheet-like negative electrode 22, and a sheet-like separator 23 are prepared. The prepared positive electrode 21, negative electrode 22, and separator 23 are spirally wound to produce a battery element 20 having a spiral electrode structure.

[0020] The fabricated battery element 20 is inserted into the outer can 10 from the open end 11 side and housed therein. Before housing the battery element 20, an insulating plate 40 is provided on the bottom inside the outer can 10. After housing the battery element 20, an insulating plate 50 is provided on the top of the battery element 20 inside the outer can 10.

[0021] Also, a sealing body 60 is prepared to which a positive electrode terminal 80 and a washer 90 are fixed via a gasket 70. A positive electrode tab 21a connected to the positive electrode 21 of the battery element 20 is connected to the positive electrode terminal 80. A negative electrode tab 22a connected to the negative electrode 22 of the battery element 20 is connected to the inner wall of the outer can 10.

[0022] A predetermined electrolyte solution 30 is poured into the exterior can 10 housing the battery element 20 connected in this manner. The sealing body 60 is fitted into the open end 11 of the exterior can 10. Then, the side wall portion 62 of the sealing body 60 and the end 11 of the exterior can 10 are welded using a method such as laser welding to form a welded joint 100. This achieves a sealed container structure in which the exterior can 10 is sealed by the sealing body 60 provided with the gasket 70, positive electrode terminal 80, and washer 90.

[0023] For example, a cylindrical battery 1 is manufactured using this method. For example, if the cylindrical battery 1 is a lithium battery or a lithium ion battery, during discharge, lithium is taken up by ion conduction from the negative electrode 22 through the separator 23 to the positive electrode 21. Furthermore, if the cylindrical battery 1 is a rechargeable battery such as a lithium ion battery, during charge, lithium is taken up by ion conduction from the positive electrode 21 through the separator 23 to the negative electrode 22. In the cylindrical battery 1, for example, discharge operation or charge / discharge operation is realized by such ion conduction of lithium.

[0024] In the cylindrical battery 1 described above, abnormal heat generation may occur if an internal short circuit occurs between the positive electrode 21 and negative electrode 22 of the battery element 20 or if the battery is subjected to external physical shock, such as being dropped. Abnormal heat generation can cause gas generation due to evaporation of the electrolyte 30 and thermal expansion of the gas within the sealed container formed by the outer can 10 and sealing body 60, which can increase the internal pressure within the sealed container. In the cylindrical battery 1, if the welding strength between the outer can 10 and sealing body 60 is insufficient, the weld 100 between the outer can 10 and sealing body 60 may not be able to withstand the internal pressure when the internal pressure increases, which could result in the cylindrical battery 1 exploding or catching fire.

[0025] Although not shown here, a technique is known in which a cylindrical battery 1 is provided with a gas release valve (also called an "explosion-proof valve") in the sealing body 60, and when the internal pressure in the sealed container formed by the outer can 10, sealing body 60, etc. rises, the gas release valve opens to release the internal gas to the outside. The valve operating pressure of the gas release valve is preferably in the range of 2.2 MPa to 5 MPa. However, if the welding strength between the outer can 10 and sealing body 60 is insufficient and the welded joint 100 cannot withstand the internal pressure before the gas release valve opens, there is a risk of the cylindrical battery 1 exploding.

[0026] Furthermore, if the welding strength between the outer can 10 and the sealing body 60 is insufficient, cracks may occur in the welded joint 100 when an impact is applied due to dropping or the like, which may lead to leakage of the electrolyte 30 or the intrusion of water, which may result in a decrease in the performance of the cylindrical battery 1.

[0027] In view of the above, the following configuration is adopted to realize a cylindrical battery 1 with excellent welding strength between the outer can 10 and the sealing body 60. 2 is a diagram illustrating an example of a welded outer can and sealing body, and is a schematic enlarged view of part P in FIG.

[0028] 2, the sealing body 60 is fitted into the open end 11 of the outer can 10. The side wall portion 62 of the sealing body 60 and the end 11 of the outer can 10 are welded, for example, by laser welding. The outer can 10 and the sealing body 60 are welded and fixed together by a welded portion 100 formed by laser welding.

[0029] In laser welding, a structure in which the sealing body 60 is fitted into the outer can 10 is irradiated with laser light 200. The laser light 200 is irradiated so that an optical axis 210 of the laser light 200 is positioned on at least one of the outer can 10 and the sealing body 60.

[0030] For example, the laser beam 200 is irradiated so that its optical axis 210 is positioned on either the outer can 10 or the sealing body 60. As an example, when the outer can 10 and the sealing body 60 are made of materials with different thermal conductivities, the laser beam 200 is irradiated so that its optical axis 210 is positioned on the material having a higher thermal conductivity and which is less likely to melt when heated by the irradiation of the laser beam 200. That is, the laser beam 200 is irradiated so that its optical axis 210 is positioned on a predetermined side of the boundary Q between the outer can 10 and the sealing body 60, either the outer can 10 side or the sealing body 60 side. FIG. 2 illustrates, as an example, a case where the optical axis 210 of the laser beam 200 is positioned on the outer can 10 side by a distance A from the boundary Q between the outer can 10 and the sealing body 60.

[0031] 2 is an example. The position of the optical axis 210 of the laser beam 200 can be set on the outer can 10 side with respect to the boundary Q, or on the sealing body 60 side with respect to the boundary Q, or even at the boundary Q. However, when the position of the optical axis 210 of the laser beam 200 is set at the boundary Q, attention should be paid to the laser beam 200 reaching the inside of the container through the boundary Q. If the position of the optical axis 210 of the laser beam 200 is set at either the outer can 10 side or the sealing body 60 side with respect to the boundary Q, for example, the side that is more difficult to melt, it is possible to prevent the laser beam 200 from reaching the inside of the container through the boundary Q, and also to make the cross-sectional area of ​​the welded joint 100 to be formed (welded area S, S1, or S2, described below) relatively large and the depth (welded depth D, described below) relatively shallow.

[0032] The welded portion 100 formed by irradiation with the laser light 200 is inside the outer can 10 and the sealing body 60 and extends in a direction T (first direction) along a boundary Q between the outer can 10 and the sealing body 60. Here, the maximum weld depth from the outermost surface of the welded portion 100 in the direction T is defined as a weld depth D of the welded portion 100.

[0033] Furthermore, the area of ​​the welded portion 100 in a cross section when the welded portion 100 is cut in direction T, i.e., in a cross section perpendicular to the plane of boundary Q as shown in Fig. 2, is defined as the welded area S of the welded portion 100. Here, the area of ​​the welded portion 100 on the outer can 10 side with respect to boundary Q is defined as welded area S1, and the area of ​​the welded portion 100 on the sealing body 60 side with respect to boundary Q is defined as welded area S2. The welded area S of the welded portion 100 is the sum of the welded area S1 on the outer can 10 side with respect to boundary Q and the welded area S2 on the sealing body 60 side with respect to boundary Q, i.e., S = S1 + S2.

[0034] In laser welding, for example, while nitrogen gas is sprayed onto the outer can 10 and the sealing body 60 to be welded, a laser welder irradiates the outer can 10 and the sealing body 60 with laser light 200 to weld them together. For example, while spraying nitrogen gas, the laser light 200 is irradiated all around to weld the outer can 10 and the sealing body 60 together. For example, since the start of irradiation of the laser light 200 consumes energy to heat the sealing body 60 and the outer can 10, an overlap angle may be set so that the laser light 200 hits the start of irradiation of the laser light 200 twice to ensure uniformity in the welding. In laser welding, various conditions are set, such as the position of the optical axis 210 of the laser light 200, the laser output, the moving (welding) speed, the overlap angle, and the amount of nitrogen gas sprayed during welding.

[0035] In laser welding, various conditions such as the position of the optical axis 210 of the laser beam 200, the laser output, the welding speed, the overlap angle, and the amount of nitrogen gas sprayed during welding are adjusted to adjust the shape of the welded portion 100, i.e., the weld depth D and the welded area S (welded areas S1 and S2). These various conditions adjust the amount of thermal energy imparted to the outer casing 10 and the sealing body 60 to be welded, thereby adjusting the weld depth D and the welded area S (or S1 and S2) of the welded portion 100.

[0036] In the cylindrical battery 1, when the thickness of the outer can 10 (its end 11) is B1 and the thickness of the sealing body 60 (its side wall 62) is B2, the welds 100 are formed so that the value obtained by dividing the weld depth D (maximum weld depth from the outermost surface) of these welds 100 by the maximum thickness (Max(B1,B2)) of thickness B1 and thickness B2 is 0.4 or more. That is, in the cylindrical battery 1, the welds 100 are formed so as to satisfy the relationship of the following formula (1).

[0037] D / Max(B1,B2)≧0.4 (1) In order to form such a welded joint 100, the conditions during laser welding (such as the position of the optical axis 210 of the laser beam 200, the laser output, the welding speed, the overlap angle, and the amount of nitrogen gas sprayed during welding) are adjusted.

[0038] In the cylindrical battery 1, the formation of the welded portion 100 that satisfies the relationship of formula (1) makes it possible to weld the outer can 10 and the sealing body 60 with excellent strength, making it possible to prevent explosions and the like at high temperatures or during over-discharge (forced discharge).

[0039] Here, in the cylindrical battery 1, it is not necessary to make the welding depth D excessively deep or to irradiate the laser light 200 excessively in order to satisfy the relationship of formula (1). In other words, in the cylindrical battery 1, as long as the relationship of formula (1) is satisfied, it is not necessary to make the welding depth D excessively deep or to irradiate the laser light 200 excessively in order to deepen the welding depth D. This is for the following reason.

[0040] For example, one method for increasing the weld strength between the outer can 10 and the sealing body 60 is to increase the weld depth D of the weld 100 (in other words, increase the weld volume or weld area S). However, this requires applying a large amount of thermal energy to the outer can 10 and the sealing body 60 by irradiating them with laser light 200 during laser welding. This application of large amounts of thermal energy may cause deformation of the resin gasket 70, evaporation of the electrolyte 30, formation of pinholes in the weld 100, early deterioration of the laser welder, etc. Furthermore, if the weld depth D of the weld 100 is made excessively deep, there is a risk that the height of the outer can 10 or the height of the cylindrical battery 1 may become lower than specified.

[0041] In contrast, in the cylindrical battery 1, if the relationship of formula (1) is satisfied, it is possible to eliminate the need for excessive welding depth D of the welded portion 100 or irradiation of laser light 200, which could lead to the above-mentioned problems caused by the application of large amounts of thermal energy. In the cylindrical battery 1, if the relationship of formula (1) is satisfied, it is possible to set the welding depth D of the welded portion 100 and the irradiation of laser light 200 within a range that avoids the above-mentioned problems, i.e., within a range that is not excessive. Therefore, it is possible to realize a highly safe cylindrical battery 1 that has excellent welding strength between the outer can 10 and the sealing body 60 and can effectively prevent rupture and the like, while avoiding the above-mentioned problems caused by the application of large amounts of thermal energy.

[0042] In addition, in the cylindrical battery 1, the welding area S of the welding portion 100 (the welding area in the cross section when cut in the direction T along the boundary Q) is calculated by multiplying the square of the maximum thickness of the thickness B1 and the thickness B2 (Max(B1, B2) 2 The welded joint 100 is formed so that the value obtained by dividing by (1 / (2)) is 0.25 or more. That is, in the cylindrical battery 1, the welded joint 100 is formed so as to satisfy the relationship of the following formula (2).

[0043] S / Max(B1,B2) 2 ≧0.25 (2) In order to form such a welded joint 100, the conditions during laser welding (such as the position of the optical axis 210 of the laser beam 200, the laser output, the welding speed, the overlap angle, and the amount of nitrogen gas sprayed during welding) are adjusted.

[0044] In the cylindrical battery 1, the formation of the welded portion 100 that satisfies the relationship of formula (2) makes it possible to weld the outer can 10 and the sealing body 60 with excellent strength, making it possible to prevent explosions and the like at high temperatures or during over-discharge.

[0045] Here, in the cylindrical battery 1, satisfying the relationship of formula (2) does not require excessively increasing the welding area S of the welded portion 100 or excessively irradiating the laser beam 200 to increase the welding area S. In other words, if the relationship of formula (2) is satisfied, in the cylindrical battery 1, it is not necessary to excessively increase the welding area S of the welded portion 100 or excessively irradiate the laser beam 200 to increase the welding area S. In the cylindrical battery 1, if the relationship of formula (2) is satisfied, the welding area S of the welded portion 100 and the irradiation of the laser beam 200 can be set within a range that avoids the above-mentioned problems caused by the application of large thermal energy, i.e., within a range that is not excessive. This makes it possible to realize a highly safe cylindrical battery 1 that has excellent welding strength between the outer can 10 and the sealing body 60 and can effectively prevent rupture and other problems while avoiding the above-mentioned problems caused by the application of large thermal energy.

[0046] In addition, in the cylindrical battery 1, when materials having different thermal conductivities are used for the outer can 10 and the sealing body 60, the welding area Sx (x=1 or 2) on the side of the boundary Q of the welded portion 100 where the material with the lower thermal conductivity, i.e., the material that melts more easily, is used is determined by dividing the welding area Sx by the square of the maximum thickness of the thickness B1 and the thickness B2 (Max(B1,B2) 2 The welded joint 100 is formed so that the value obtained by dividing by (1 / (2)) is 0.13 or more. That is, in the cylindrical battery 1, the welded joint 100 is formed so as to satisfy the relationship of the following formula (3).

[0047] Sx / Max(B1,B2) 2 ≧0.13 (3) In formula (3), x is 1 or 2, and is 1 if the outer can 10 is made of a material having a lower thermal conductivity than the sealing body 60, and is 2 if the sealing body 60 is made of a material having a lower thermal conductivity than the outer can 10.

[0048] The conditions for laser welding (such as the position of the optical axis 210 of the laser beam 200, the laser output, the welding speed, the overlap angle, and the amount of nitrogen gas sprayed during welding) are adjusted so as to form such a welded joint 100. When materials having different thermal conductivities are used for the outer can 10 and the sealing body 60, the optical axis 210 of the laser beam 200 is adjusted so as to be positioned on the side using the material with the higher thermal conductivity, i.e., the side that is less likely to melt when heated by the irradiation of the laser beam 200.

[0049] When the optical axis 210 of the laser beam 200 is adjusted to this position, the welding area Sx of the outer can 10 and the sealing body 60 on the side where a material with low thermal conductivity, i.e., a material that melts easily, is used tends to be relatively large, and the welding depth D of the welded portion 100 tends to be relatively shallow. In the cylindrical battery 1, even if the welding depth D of the welded portion 100 is relatively shallow, the welding area Sx is relatively large, so that the welding strength between the outer can 10 and the sealing body 60 is ensured.

[0050] In the cylindrical battery 1, the formation of the welded portion 100 that satisfies the relationship of formula (3) makes it possible to weld the outer can 10 and the sealing body 60 with excellent strength, making it possible to prevent explosions and the like at high temperatures or during over-discharge.

[0051] Here, in the cylindrical battery 1, satisfying the relationship of formula (3) does not require excessively increasing the welding area Sx (x = 1 or 2) at the welded portion 100 or excessively irradiating the laser beam 200 to increase the welding area Sx. In other words, if the relationship of formula (3) is satisfied, in the cylindrical battery 1, it is not necessary to excessively increase the welding area Sx at the welded portion 100 or excessively irradiate the laser beam 200 to increase the welding area Sx. In the cylindrical battery 1, if the relationship of formula (3) is satisfied, the welding area Sx at the welded portion 100 and the irradiation of the laser beam 200 can be set within a range that avoids the above-mentioned problems caused by the application of large thermal energy, i.e., within a range that is not excessive. This makes it possible to realize a highly safe cylindrical battery 1 that has excellent welding strength between the outer can 10 and the sealing body 60 and can effectively prevent rupture and other problems while avoiding the above-mentioned problems caused by the application of large thermal energy.

[0052] Comparative Examples and Examples will be described below. Here, lithium batteries (lithium primary batteries) were formed as cylindrical batteries 1 having the configuration shown in Figure 1 above for Comparative Example 1 and Examples 1-4, with the CR17335 type being the smallest size and the CR17500 type being the largest size.

[0053] [Table 1]

[0054] Table 1 shows the combinations of materials for the outer can 10 and the sealing body 60 used in the cylindrical batteries 1 of Comparative Example 1 and Examples 1-4.

[0055] [Table 2]

[0056] Table 2 shows the thickness B1 of the outer can 10 and the thickness B2 of the sealing body 60 used in the cylindrical batteries 1 of Comparative Example 1 and Examples 1-4. Table 2 also shows the welding depth D (maximum welding depth from the outermost surface) of the welded portion 100 in the cylindrical batteries 1 of Comparative Example 1 and Examples 1-4, as well as the values ​​of D / Max(B1, B2) and S / Max(B1, B2). 2 Value of Sx / Max(B1,B2) 2 Table 2 also shows whether or not the cylindrical batteries 1 of Comparative Example 1 and Examples 1-4 exploded in the forced discharge or overdischarge test (JIS C 8513 2020) ("exploded" or "no explosion").

[0057] <Comparative Example 1> An outer can 10 made of nickel (Ni)-plated steel (referred to as "Ni-plated steel") (Table 1) was prepared, which had a cylindrical shape with a bottom and an open end 11. The Ni-plated steel of the outer can 10 had a thickness B1 of 0.3 mm (Table 2). The outer can 10 was a CR17335 type, with an outer diameter of 17.0 mm and a height of 33.5 mm. The thermal conductivity of pure iron is approximately 67 W / m / °C (100°C).

[0058] Gasket 60 was prepared using ferritic stainless steel containing chromium (Cr) (referred to as "Cr-containing ferritic stainless steel"), commonly known as SUS430 (Table 1). Gasket 60 had a disk-shaped bottom plate 61 with opening 61a and a side wall 62 around its periphery. The Cr-containing ferritic stainless steel (SUS430) used for gasket 60 had a thickness B2 of 0.3 mm (Table 2). The thermal conductivity of Cr-containing ferritic stainless steel (SUS430) is approximately 25.6 W / m / °C (100°C).

[0059] A positive electrode terminal 80 and a washer 90 were attached to the opening 61a of the sealing body 60 via a gasket 70. The insulating plate 40, the battery element 20, and the insulating plate 50 were placed inside the outer can 10 through the opening on one end side of the outer can 10. The positive electrode tab 21a was connected to the positive electrode terminal 80, and the negative electrode tab 22a was connected to the inner wall of the outer can 10. After pouring the electrolyte 30, the sealing body 60 was fitted into the opening on one end side of the outer can 10. Then, the end 11 on one end side of the outer can 10 and the side wall portion 62 of the sealing body 60 fitted therein were welded by laser welding to form a weld 100.

[0060] In this way, the cylindrical battery 1 of Comparative Example 1 was obtained. In the cylindrical battery 1 of Comparative Example 1, the welded portion 100 was formed by adjusting the conditions during laser welding, and the weld depth D of the formed welded portion 100 was D = 0.080 mm (Table 2).

[0061] In the cylindrical battery 1 of Comparative Example 1, Max(B1, B2) = 0.3 mm. In the cylindrical battery 1 of Comparative Example 1, D / Max(B1, B2) = 0.267 (Table 2). In addition, in the cylindrical battery 1 of Comparative Example 1, S / Max(B1, B2) 2 = 0.09 (Table 2), and when Sx = S2 (x = 2), Sx / Max(B1, B2) 2 =S2 / Max(B1,B2) 2 =0.04 (Table 2).

[0062] When a predetermined forced discharge test (JIS C 8513 2020) was carried out on the cylindrical battery 1 of Comparative Example 1, rupture was observed. Example 1 An outer can 10 made of Ni-plated steel (Table 1) was prepared, having a cylindrical shape with a bottom and an open end 11. The Ni-plated steel of the outer can 10 had a thickness B1 of 0.3 mm (Table 2). The outer can 10 was a CR17335 type, with an outer diameter of 17.0 mm and a height of 33.5 mm.

[0063] Gasket 60 was prepared using Cr-containing ferritic stainless steel, commonly known as SUS430 (Table 1), and had a disk-shaped bottom plate 61 with opening 61a and a side wall 62 around the bottom plate. The Cr-containing ferritic stainless steel (SUS430) used for gasket 60 had a thickness B2 of 0.3 mm (Table 2).

[0064] A positive electrode terminal 80 and a washer 90 were attached to the opening 61a of the sealing body 60 via a gasket 70. An insulating plate 40, a battery element 20, and an insulating plate 50 were placed inside the outer can 10 through the opening on one end side. The positive electrode tab 21a was connected to the positive electrode terminal 80, and the negative electrode tab 22a was connected to the inner wall of the outer can 10. After the electrolyte 30 was poured, the sealing body 60 was fitted into the opening on one end side of the outer can 10. Then, the edge 11 on one end side of the outer can 10 and the side wall portion 62 of the sealing body 60 fitted therein were welded by laser welding to form a weld 100. In the laser welding, the optical axis 210 of the laser beam 200 was positioned on the outer can 10 side with respect to the boundary Q between the outer can 10 and the sealing body 60, and the laser beam 200 was irradiated.

[0065] In this way, the cylindrical battery 1 of Example 1 was obtained. In the cylindrical battery 1 of Example 1, the welded portion 100 was formed by adjusting the conditions during laser welding, and the weld depth D of the formed welded portion 100 was D = 0.120 mm (Table 2).

[0066] In the cylindrical battery 1 of Example 1, Max(B1, B2) = 0.3 mm. In the cylindrical battery 1 of Example 1, D / Max(B1, B2) = 0.400 (Table 2). In addition, in the cylindrical battery 1 of Example 1, S / Max(B1, B2) 2 = 0.25 (Table 2), and when Sx = S2 (x = 2), Sx / Max(B1, B2) 2 =S2 / Max(B1,B2) 2 =0.13 (Table 2).

[0067] When the cylindrical battery 1 of Example 1 was subjected to a predetermined forced discharge test (JIS C 8513 2020), no rupture was observed. <Example 2> An outer can 10 made of Ni-plated steel (Table 1) was prepared, having a cylindrical shape with a bottom and an open end 11. The Ni-plated steel of the outer can 10 had a thickness B1 of 0.3 mm (Table 2). The outer can 10 was a CR17335 type, with an outer diameter of 17.0 mm and a height of 33.5 mm.

[0068] Gasket 60 was prepared using Cr-containing ferritic stainless steel, commonly known as SUS430 (Table 1), and had a disk-shaped bottom plate 61 with opening 61a and a side wall 62 around the bottom plate. The Cr-containing ferritic stainless steel (SUS430) used for gasket 60 had a thickness B2 of 0.3 mm (Table 2).

[0069] Using such an outer can 10 and sealing body 60, a cylindrical battery 1 of Example 2 was obtained in the same manner as in Example 1, having a weld 100 formed by laser welding the outer can 10 and sealing body 60. In the cylindrical battery 1 of Example 2, the weld 100 was formed by adjusting the conditions during laser welding, and the weld depth D of the formed weld 100 was D = 0.157 mm (Table 2).

[0070] In the cylindrical battery 1 of Example 2, Max(B1, B2) = 0.3 mm. In the cylindrical battery 1 of Example 2, D / Max(B1, B2) = 0.523 (Table 2). In addition, in the cylindrical battery 1 of Example 2, S / Max(B1, B2) 2 = 0.43 (Table 2), and when Sx = S2 (x = 2), Sx / Max(B1, B2) 2 =S2 / Max(B1,B2) 2 =0.22 (Table 2).

[0071] When the cylindrical battery 1 of Example 2 was subjected to a predetermined forced discharge test (JIS C 8513 2020), no rupture was observed. Example 3 An outer can 10 made of Ni-plated steel (Table 1) was prepared, having a cylindrical shape with a bottom and an open end 11. The Ni-plated steel of the outer can 10 had a thickness B1 of 0.3 mm (Table 2). The outer can 10 was a CR17450 type, with an outer diameter of 17.0 mm and a height of 45.0 mm.

[0072] Gasket 60 was prepared using austenitic stainless steel containing Cr, Ni, and molybdenum (Mo) (referred to as "Cr-, Ni-, and Mo-containing austenitic stainless steel"), commonly known as SUS316 (Table 1). Gasket 60 had a disk-shaped bottom plate 61 with an opening 61a and a side wall 62 around its periphery. The Cr-, Ni-, and Mo-containing austenitic stainless steel (SUS316) used for gasket 60 had a thickness B2 of 0.3 mm (Table 2). The thermal conductivity of Cr-, Ni-, and Mo-containing austenitic stainless steel (SUS316) is approximately 16.7 W / m / °C (100°C).

[0073] Using such an outer can 10 and sealing body 60, a cylindrical battery 1 of Example 3 was obtained in the same manner as in Example 1, having a weld 100 formed by laser welding the outer can 10 and sealing body 60. In the cylindrical battery 1 of Example 3, the weld 100 was formed by adjusting the conditions during laser welding, and the weld depth D of the formed weld 100 was D = 0.142 mm (Table 2).

[0074] In the cylindrical battery 1 of Example 3, Max(B1, B2) = 0.3 mm. In the cylindrical battery 1 of Example 3, D / Max(B1, B2) = 0.473 (Table 2). In addition, in the cylindrical battery 1 of Example 3, S / Max(B1, B2) 2 = 0.40 (Table 2), and when Sx = S2 (x = 2), Sx / Max(B1, B2) 2 =S2 / Max(B1,B2) 2 =0.22 (Table 2).

[0075] When the cylindrical battery 1 of Example 3 was subjected to a predetermined forced discharge test (JIS C 8513 2020), no explosion was observed. Example 4 An outer can 10 (Table 1) was prepared using tin (Sn)-added Cr-containing ferritic stainless steel (referred to as "Sn-added Cr-containing ferritic stainless steel"), and had a bottomed, cylindrical shape with one end 11 open. The Sn-added Cr-containing ferritic stainless steel used for the outer can 10 had a thickness B1 of 0.25 mm (Table 2). The outer can 10 was CR17500 type, with an outer diameter of 17.4 mm and a height of 50.0 mm. The thermal conductivity of the Sn-added Cr-containing ferritic stainless steel was approximately 25.6 W / m / °C (100°C).

[0076] Gasket 60 was prepared using Cr-containing ferritic stainless steel, commonly known as SUS430 (Table 1), and had a disk-shaped bottom plate 61 with opening 61a and a side wall 62 around the bottom plate. The Cr-containing ferritic stainless steel (SUS430) used for gasket 60 had a thickness B2 of 0.3 mm (Table 2).

[0077] Using such an outer can 10 and sealing body 60, a cylindrical battery 1 of Example 4 was obtained in the same manner as in Example 1, having a weld 100 formed by laser welding the outer can 10 and sealing body 60. In the cylindrical battery 1 of Example 4, the weld 100 was formed by adjusting the conditions during laser welding, and the weld depth D of the formed weld 100 was D = 0.125 mm (Table 2).

[0078] In the cylindrical battery 1 of Example 4, Max(B1, B2) = 0.3 mm. In the cylindrical battery 1 of Example 4, D / Max(B1, B2) = 0.417 (Table 2). In addition, in the cylindrical battery 1 of Example 4, S / Max(B1, B2) 2 = 0.28 (Table 2), and when Sx = S2 (x = 2), Sx / Max(B1, B2) 2 =S2 / Max(B1,B2) 2 =0.13 (Table 2).

[0079] When the cylindrical battery 1 of Example 4 was subjected to a predetermined forced discharge test (JIS C 8513 2020), no explosion was observed. <Evaluation> The results of Comparative Example 1 and Examples 1-4 above confirm that the cylindrical batteries 1 of Examples 1-4, which satisfy D / Max(B1, B2)≧0.4, i.e., satisfy the relationship of formula (1), are more effective in preventing explosions even under forced discharge conditions than the cylindrical battery 1 of Comparative Example 1, which does not satisfy this relationship. It can also be said that the cylindrical battery 1 is more effective in preventing explosions even under forced discharge conditions when the weld depth D of the welded portion 100 is at least 0.120 mm.

[0080] Also, S / Max(B1,B2) 2 ≧0.25, i.e., satisfying the relationship of the above formula (2), it was confirmed that the cylindrical battery 1 of Example 1-4 can effectively suppress explosion even under forced discharge conditions, compared to the cylindrical battery 1 of Comparative Example 1, which does not satisfy this relationship.

[0081] Also, Sx / Max(B1,B2) 2 ≧0.13, i.e., satisfying the relationship of the above formula (3) (where Sx=S2), it was confirmed that the cylindrical battery 1 of Example 1-4 can effectively suppress rupture even under forced discharge conditions, compared to the cylindrical battery 1 of Comparative Example 1 which does not satisfy this relationship.

[0082] Therefore, by forming the weld 100 between the outer can 10 and the sealing body 60 by laser welding so that the weld 100 satisfies the relationship of formula (1) above, or further the relationship of formula (2) or (3) above, it can be said that a highly safe cylindrical battery 1 can be realized in which the weld strength of the weld 100 is excellent and rupture is effectively suppressed.

[0083] The method for forming the welded portion 100 described above is not limited to the lithium batteries described in Examples 1-4, etc., and can be applied to forming a welded portion between an outer can and a sealing member in various types of batteries, such as lithium ion batteries, alkaline batteries, and nickel-metal hydride batteries, as long as the battery uses a cylindrical outer can with a bottom and a sealing member that seals it. The battery element housed in the sealed container formed by the welded outer can and sealing member is not limited to battery element 20 with a spiral electrode structure as shown in Fig. 1 above, but battery elements having various configurations depending on the type of battery can be used. [Explanation of symbols]

[0084] 1 Cylindrical battery 10 Outer can 11 End 20 Battery elements 21 Positive electrode 21a Positive electrode tab 22 Negative electrode 22a Negative electrode tab 23 Separator 30 Electrolyte 40, 50 Insulating plate 60 Sealing body 61 Bottom plate part 61a opening 62 Side wall 70 Gasket 80 Positive terminal 90 Washer 100 Welded Section 200 Laser Light 210 Optical axis A. Distance B1, B2 thickness D Welding depth (maximum welding depth) Q boundary S, Sx, S1, S2 Welding area T direction (first direction)

Claims

1. A battery element; a cylindrical outer can having an opening at one end and a bottom in which the battery element is housed; a sealing body that seals the one end of the outer can; a weld portion that welds the outer can and the sealing body and extends in a first direction along a boundary between the outer can and the sealing body; Including, a value obtained by dividing a maximum weld depth from an outermost surface of the weld in the first direction by a maximum thickness among a thickness of the outer can and a thickness of the sealing body is 0.4 or more.

2. 2 . The cylindrical battery according to claim 1 , wherein a value obtained by dividing a welding area of ​​the welded portion in a cross section of the welded portion cut in the first direction by the square of the maximum thickness is 0.25 or more.

3. the outer can and the sealing body have different thermal conductivities, 2. The cylindrical battery according to claim 1, wherein a value obtained by dividing a welding area of ​​the outer can or the sealing body having a smaller thermal conductivity at the welded portion in a cross section of the welded portion cut in the first direction by the square of the maximum thickness of the welded portion is 0.13 or more.

4. The outer can is made of steel or stainless steel, 2. The cylindrical battery according to claim 1, wherein the sealing member is made of stainless steel.

5. 2. The cylindrical battery according to claim 1, wherein the maximum weld depth is 0.120 mm or greater.

6. the sealing body has a bottom plate portion and a side wall portion rising from an outer periphery of the bottom plate portion, the side wall portion is provided along an inner wall of the outer can at the end portion on the one end side, The cylindrical battery according to claim 1 , wherein the boundary between the exterior can and the sealing body is the boundary between the end portion and the side wall portion.

7. A method for manufacturing the cylindrical battery according to any one of claims 1 to 6, The method for manufacturing a cylindrical battery includes forming the welded portion by irradiating at least one of the outer can and the sealing body with a laser in the first direction.

8. 8. The method for manufacturing a cylindrical battery according to claim 7, wherein, when welding the outer can and the sealing body having different thermal conductivities, the optical axis of the laser light during the laser irradiation is positioned at the outer can or the sealing body having the greater thermal conductivity.

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