Battery

Abstract

A battery according to the present invention is provided with: a battery can which is formed of a metal and comprises a cylindrical part having an open edge at one end, and a bottom part that closes the other end of the cylindrical part; an electrode body which is contained in the cylindrical part; and a sealing member which is joined to the open edge so as to seal the opening of the open edge. The sealing member comprises: a gasket part; a disk part that is formed of a metal; a ring part that swages the disk part to a center part by the intermediary of the gasket part; and an intermediate member that is joined to the upper surface of the ring part.

Description

battery

[0001] The present disclosure relates to batteries.

[0002] Various configurations of sealed batteries have been known in the past (see, for example, Patent Document 1). Such conventional batteries have a battery can with an open end, and the open end of the battery can is sealed. The following method is known as a method for sealing the open end. For example, after an electrode assembly is housed in the battery can, the battery can is narrowed inward near the open end of the battery can. This narrowing forms an annular protrusion on the inner peripheral surface of the battery can, and a gasket and a sealing member are placed on this protrusion. Then, the open end of the battery can is crimped to the sealing member via the gasket, forming a crimped portion on the sealing member. This seals the battery, producing a sealed battery.

[0003] Japanese Unexamined Patent Publication No. 7-105933

[0004] However, in a battery having a groove and a crimped portion, the sealing member is placed on the groove, and the crimped portion is formed on the sealing member via a gasket, which tends to increase the height dimension of the battery near the sealing plate.As a result, the battery described in Patent Document 1 has a problem in that the energy density tends to decrease.

[0005] Therefore, an object of the present disclosure is to provide a battery that can achieve an improvement in energy density by solving the above-mentioned conventional problems.

[0006] The battery according to the present disclosure includes a metal battery can having a cylindrical portion with an opening edge at one end and a bottom portion that closes the other end of the cylindrical portion, an electrode assembly housed inside the cylindrical portion, and a sealing member that is joined to the opening edge of the battery can and seals the opening at the opening edge. The sealing member includes a gasket portion, a metal disk portion, a ring portion with the disk portion crimped to the center via the gasket portion, and an intermediate member joined to the upper surface of the ring portion.

[0007] According to the battery according to the present disclosure, it is possible to achieve an improvement in the energy density of the battery.

[0008] 1A is a schematic perspective cross-sectional view showing the cross-sectional structure of a battery according to a first embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view showing the cross-sectional view of FIG. 1A taken along the Z-X plane. FIG. 1A is a schematic perspective cross-sectional view showing the appearance of a sealing member in the battery according to the first embodiment, and FIG. 1B is a partial cross-sectional view showing a portion of the cross-sectional structure of the sealing member of FIG. 1A taken along the A-A direction. FIG. 1A to FIG. 1C are schematic partial cross-sectional views showing steps in a method for manufacturing a sealing member. FIG. 1A is a schematic perspective cross-sectional view showing the cross-sectional structure of a battery according to a first variation of the first embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view showing the cross-sectional view of FIG. 1A taken along the Z-X plane. FIG. 1A is a schematic perspective cross-sectional view showing the cross-sectional structure of a battery according to a second variation of the first embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view showing the cross-sectional view of FIG. 1A taken along the Z-X plane. 1A is a schematic perspective cross-sectional view showing a cross-sectional structure of a battery according to a third modification of the first embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view showing the cross-sectional view of FIG. 1A taken along the Z-X plane.

[0009] (Background to the present disclosure) In conventional battery sealing methods, the formation of a crimped portion results in an increase in the longitudinal dimension of the battery near the sealing member, and a decrease in the energy density of the battery. Therefore, in order to solve the conventional problems, the inventors investigated a sealed battery in which the battery can can be sealed without forming a crimped portion by joining the battery can and the sealing member by, for example, welding.

[0010] Specifically, the inventors investigated a method of sealing the battery can by inserting a sealing member into the edge of the opening of the battery can and welding the butted surfaces.

[0011] A battery sealing member typically consists of a gasket made of resin (e.g., polypropylene) crimped with a metal member several hundred microns thick. When attempting to weld such a sealing member to a battery can, the heat generated by the welding is applied to the gasket crimped within the sealing member, causing the gasket to thermally deform and melt, resulting in poor airtightness. Here, we will explain in detail how the temperature of the gasket rises. The temperature of the welded portion formed by butt-welding the edge of the opening edge to the outer peripheral edge of the sealing member rises to the melting point of the metal material used in the battery can and the sealing member (e.g., the melting point of iron is approximately 1500°C). Meanwhile, the gasket is crimped with a metal member several hundred microns thick, and the distance to the weld is also several hundred microns. For example, if the gasket is made of polypropylene, its melting point is 140°C, which is approximately 1400°C higher than the welded portion, potentially causing the gasket to melt during welding.

[0012] Next, the problems caused by melting of the gasket will be described in detail. As mentioned above, the sealing member is a gasket crimped with a metal member several hundred microns thick. The crimping process seals two metal parts with different potentials in a battery while insulating them, by crushing the resin with the metal member, and sealing is achieved by the repulsive force of the resin. If the gasket melts due to welding, the gasket melts while being crushed by the metal member, and the molten resin material may leak out, preventing the resin from maintaining a sealed state and reducing airtightness. If the airtightness of the sealing member decreases, the safety of the battery will also decrease, so it is necessary to avoid melting the gasket when sealing the battery.

[0013] Therefore, the present inventors have investigated the battery according to the present disclosure as described below as a battery that can solve such problems.

[0014] A battery according to one aspect of the present disclosure includes a metal battery can, an electrode assembly, an electrolyte, and a sealing member. The battery can has a cylindrical portion with an opening edge at one end and a bottom portion that closes the other end of the cylindrical portion. The electrode assembly is housed in the battery can. The battery can is filled with an electrolyte. The sealing member seals the opening edge of the cylindrical portion of the battery can. The sealing member is fixed so that its outer peripheral surface faces the inner peripheral surface of the opening edge. Specifically, the fixing is achieved by joining a portion of the inner peripheral surface of the opening edge and a portion of the outer peripheral surface of the sealing member by a fusion zone. In addition, an intermediate member made of a metal material having a melting point lower than the melting point of the metal material of the sealing member is provided on the upper surface of the sealing member.

[0015] With this configuration, the intermediate member can suppress heat conduction to the gasket portion when the battery can and the sealing member are joined. In other words, when a portion of the inner circumferential surface of the opening edge and a portion of the outer circumferential surface of the sealing member are welded, the temperature rise of the gasket portion due to heat transferred to the gasket portion of the sealing member can be suppressed. By suppressing the temperature rise of the gasket portion, melting of the gasket portion can be suppressed. Therefore, poor airtightness of the sealing member due to heat during welding can be reduced. When the gasket portion melts due to welding, the gasket portion melts while being crushed by the metal member. This can lead to the molten resin material spilling out, which can cause the resin to be unable to maintain a sealed state and reduce airtightness. Therefore, the battery can can be sealed by welding, and the sealing member can be fixed to the battery can. Unlike conventional batteries, there is no need to provide an annular protrusion (also known as a reduced diameter portion) on the inner circumferential surface of the battery can or a crimping portion at the open end of the battery can, so the distance between the electrode body and the sealing member can be reduced. This allows the volume of the battery can to be reduced, and improves the energy density of the battery, which is the ratio of the battery energy to the volume of the battery can.

[0016] Each aspect of the present disclosure will be described below.

[0017] The battery according to the first aspect comprises a metal battery can having a cylindrical portion with an opening edge at one end and a bottom portion that closes the other end of the cylindrical portion, an electrode body housed inside the cylindrical portion, and a sealing member that is joined to the opening edge of the battery can and seals the opening of the opening edge portion, and the sealing member includes a ring portion having a metal disk portion crimped to its center via a gasket portion, and an intermediate member that is joined to the upper surface of the ring portion.

[0018] In a battery according to a second aspect, in the first aspect, the intermediate member may be made of a metal material having a melting point lower than the melting points of the metal of the disk portion and the metal of the battery can.

[0019] A battery according to a third aspect is the battery according to the first or second aspect, wherein the sealing member may be configured to join the ring portion and the intermediate member by a first fusion zone.

[0020] A battery according to a fourth aspect is the battery according to the third aspect, wherein the first fusion zone has a fusion area at the contact surface between the ring portion and the gasket portion that is larger than the fusion area at the interface between the ring portion and the intermediate member.

[0021] A battery according to a fifth aspect is the battery according to the third or fourth aspect, wherein the first fusion zone may be protruded toward the gasket portion on a surface where the ring portion and the gasket portion contact each other.

[0022] A battery according to a sixth aspect is any one of the first to fifth aspects, wherein the ring portion has a recess on the upper surface, and the intermediate member is joined to the ring portion so as to engage with the recess.

[0023] A seventh aspect of the battery is any one of the first to fifth aspects, wherein the intermediate member has an annular shape, and the diameter of the annular shape may be the same as the diameter of the battery can.

[0024] In the battery according to an eighth aspect, in the seventh aspect, the intermediate member may have an outer periphery with a thickness smaller than an inner periphery of the annular shape.

[0025] Batteries according to embodiments will be described below with reference to the accompanying drawings, in which substantially identical components are designated by the same reference numerals.

[0026] First Embodiment Hereinafter, a battery according to the present disclosure will be specifically described with reference to the drawings.

[0027] First, the configuration of the battery 10 will be described with reference to Fig. 1. Fig. 1(a) is a schematic perspective cross-sectional view showing the cross-sectional structure of the battery 10 according to embodiment 1. Fig. 1(b) shows a cross-sectional view of the battery 10 according to embodiment 1. For convenience, the opening side of the battery can 11 is defined as the Z direction, the direction perpendicular to the Z axis in a cross section including the Z axis is defined as the X direction, and the direction perpendicular to the Z axis and the X axis is defined as the Y direction.

[0028] As shown in FIG. 1( a ), a battery 10 according to the embodiment includes a battery can 11 , a sealing member 12 , an electrolyte 14 , and an electrode assembly 15 .

[0029] <Battery Can> The battery can 11 has a tubular portion 31 with an opening edge at one end, and a bottom portion 32 that closes the other end of the tubular portion 31. In the first embodiment, the tubular portion 31 is, for example, a cylindrical portion, and the battery can 11 is a bottomed container having a cylindrical shape with an open top end in the drawing. The battery can 11 is made of metal. The battery can 11 contains an electrode body 15, and the battery can 11 is filled with an electrolyte 14. The battery can 11 is sealed with a sealing member 12. The space inside the battery can 11 that contains the electrode body 15 and the electrolyte 14 is a sealed space. Therefore, the battery 10 according to the first embodiment is a sealed battery.

[0030] <Sealing member> The sealing member 12 forms a positive electrode portion by crimping a disk portion to the center via a gasket portion. The sealing member 12 has a disk shape, and due to the presence of an intermediate member 20 described below, the central portion is raised upward relative to the outer peripheral portion. The sealing member 12 has an outer peripheral surface that is disposed so as to face the inner peripheral surface of the battery can 11. The sealing member 12 is inserted into the battery can 11 so that the height of the top end of the sealing member 12 in the drawing generally coincides with the height of the top end of the battery can 11 in the drawing.

[0031] <Electrode body> Depending on the material, the electrode body 15 releases or absorbs electrons or ions into the battery can 11. The electrode body 15 has two types of electrodes, a positive electrode and a negative electrode, with a separator sandwiched between them to block the movement of electrons or ions, creating a three-layer structure. The electrode body 15 also has positive and negative electrode tabs through which electrons or ions flow for the positive and negative electrodes, respectively, but these are omitted from the drawings.

[0032] <Electrode Solution> The electrolyte solution 14 is a medium through which the electrons or ions emitted from the electrode body 15 can move.

[0033] <Battery Manufacturing Method> The battery 10 of the present disclosure is manufactured through the following steps. (1) First, the electrode body 15 is inserted into the battery can 11, and the electrolyte 14 is poured into it. (2) Next, as shown in FIG. 1( b), the sealing member 12 is inserted into the battery can 11 so that the upper end of the inner circumferential surface of the battery can 11 and the upper end of the outer circumferential surface of the sealing member 12 are generally aligned in the drawing. (3) Next, for example, a melting laser 16 is used to irradiate the battery can 11 and a portion of the sealing member 12. The melting laser 16 is also scanned along the circumferential direction of the outer periphery of the sealing member 12. This irradiation forms a homogeneous material molten portion 18, and the outer periphery of the sealing member 12 is joined to the inner periphery of the cylindrical portion 31. As a result, the battery can 11 is sealed, and the sealing member 12 is fixed to the battery can 11.

[0034] The battery 10 of the present disclosure is manufactured through the above steps.

[0035] <Details of Sealing Member> Next, details of the sealing member 12 of the battery can 11 will be described with reference to Fig. 2. Fig. 2(a) is a schematic perspective view showing the appearance of the sealing member 12 in the battery 10 according to embodiment 1, and Fig. 2(b) is a schematic partial cross-sectional view showing part of the cross-sectional structure of the sealing member 12 in Fig. 2(a) as viewed from the direction A-A.

[0036] 2B, the sealing member 12 includes an intermediate member 20, a ring portion 21, a gasket portion 22, and a disk portion 23. In the sealing member 12, the ring portion 21 and the disk portion 23 are made of a metal material, and the gasket portion 22 is made of a resin material.

[0037] The sealing member 12 is, for example, ring-shaped. The disk portion 23 is crimped to the ring portion 21 via the gasket portion 22. That is, as shown in Fig. 2(b) , the ring portion 21 crimps the disk portion 23 to the center of the ring portion 21 via the gasket portion 22. The sealing member 12 is electrically insulated from the disk portion 23 by the gasket portion 22.

[0038] An intermediate member 20 made of a metal material having a melting point lower than the melting point of the other metal materials of the sealing member is provided on the upper surface of the sealing member 12 .

[0039] The metal material forming the ring portion 21 is the same as that of the battery can 11. The metal material forming the intermediate member 20 is made of a metal material having a melting point lower than that of the metal material forming the ring portion 21.

[0040] In this battery 10 , the intermediate member 20 can suppress heat conduction to the gasket portion 22 when the battery can 11 and the sealing member 12 are joined together.

[0041] <Method for Manufacturing the Sealing Member> Next, a method for manufacturing the sealing member 12 will be described with reference to FIG.

[0042] 3A, the intermediate member 20 and the ring portion 21 are first overlapped and then heated and joined from the side of the ring portion 21, for example, with a laser beam. Specifically, the intermediate member 20 is attached to the top surface side of the ring portion 21, and welding is performed from the bottom surface side with a welding laser 25, forming a dissimilar material fusion zone 26.

[0043] Here, as described above, the melting point of the ring portion 21 is higher than that of the intermediate member 20, so heating is performed from the high-melting-point metallic material side. This makes it possible to suppress the amount of heat transferred to the low-melting-point side, thereby suppressing the generation of intermetallic compounds due to mixing with the metallic material on the low-melting-point side and maintaining the joining strength.

[0044] In dissimilar material fusion zone 26, the relationship between surface melt width 27 and interfacial melt width 28 at the interface between sealing material 12 and intermediate member 20 is surface melt width 27 > interfacial melt width 28. For example, if joining is performed using a laser under irradiation conditions of a wavelength of 1070 nm, an output of 250 W, a scanning speed of 500 mm / s, and a spot diameter of 20 μm, the surface melt width will be approximately 200 μm and the interfacial melt width will be approximately 150 μm.

[0045] Furthermore, due to a change in the crystal structure caused by the heat during welding, the dissimilar material fused portion 26 becomes raised by several tens of micrometers in the fusion direction compared to the surface before welding.

[0046] (b) Next, as shown in FIG. 3(b), the gasket portion 22 and the disk portion 23 are inserted into the ring portion 21.

[0047] (c) Finally, as shown in FIG. 3(c), the disk portion 23 is crimped with the ring portion 21 via the gasket portion 22, thereby completing the sealing member 12 of the battery 10.

[0048] 3( c), in the ring portion 21 to which the gasket portion 22 is crimped, the airtightness of the gasket is ensured by the close contact between the ring portion 21 and the gasket portion 22 and the close contact between the gasket portion 22 and the disk portion 23. This degree of contact improves as the gasket portion 22 is compressed and the gasket compressed length 29, which is the thickness of the gasket portion 22 sandwiched between the ring portion 21 and the disk portion 23 in the cross section of the sealing member 12, becomes smaller than the original thickness of the gasket portion 22. As described above, the dissimilar material fusion zone 26 protrudes toward the gasket portion 22, and therefore the gasket compressed length 29 at the dissimilar material fusion zone 26 is shorter than that at an unwelded position due to the protrusion of the dissimilar material fusion zone 26. Therefore, the degree of contact of the gasket is improved, and a sealing member 12 having the dissimilar material fusion zone 26 can ensure a higher airtight state.

[0049] As described above, the sealing member 12 shown in Fig. 1 has a shape in which the central portion is raised higher than the peripheral portion due to the presence of the intermediate member 20. That is, the battery 10 has a convex portion on the top surface. However, it is preferable that the battery have a flat surface.

[0050] (Variation 1) Furthermore, a sealing member according to Variation 1 of Embodiment 1 can be manufactured as follows. Fig. 4(a) is a schematic perspective cross-sectional view showing the cross-sectional structure of a battery 10a according to Variation 1 of Embodiment 1. Fig. 4(b) is a schematic cross-sectional view showing the case where the cross-sectional view of (a) is taken along the Z-X plane.

[0051] The battery 10a includes a sealing member 12a, which has an uneven top surface on a ring portion, and is manufactured so that the intermediate member 20 fits into the recessed portion of the ring portion.

[0052] The advantage of this modification 1 is that the upper surface of the sealing member 12a can be flattened, resulting in high shape stability as a battery. On the other hand, the disadvantage is that the crimping structure of the sealing member 12a becomes more complex than that of the sealing member 12 shown in FIG. 1, resulting in higher costs.

[0053] (Variation 2) Furthermore, sealing member 12b according to Variation 2 of Embodiment 1 may be manufactured as follows: Fig. 5(a) is a schematic perspective cross-sectional view showing the cross-sectional structure of battery 10b according to Variation 2 of Embodiment 1, and Fig. 5(b) is a schematic cross-sectional view showing the cross-sectional view of (a) taken along the Z-X plane.

[0054] The battery 10b includes a sealing member 12b. The sealing member 12b is manufactured so that the ring portion 21 has the same shape as in FIG.

[0055] The advantages of this modification 2 include the ability to simplify the crimping structure and flatten the top surface of the closure member 12b. Furthermore, positioning of the closure member 12b can be facilitated because the intermediate member 20a stops at the edge of the battery can 11 when inserting the closure member 12b. On the other hand, the disadvantage is that the fusion of the same-material fusion zone 18, which is the welded portion between the battery can 11 and the closure member 12b in FIG. 5(b), becomes weak, requiring some ingenuity, such as applying a stronger output to the fusion laser 16.

[0056] In this structure, it is not necessary to bond the intermediate member to the battery can, but it is sufficient that the sealing member 12b is bonded to the battery can.

[0057] (Variation 3) Furthermore, the sealing member according to Variation 3 of Embodiment 1 may be manufactured as follows: Fig. 6(a) is a schematic perspective cross-sectional view showing the cross-sectional structure of battery 10c according to Variation 3 of Embodiment 1, and (b) is a schematic cross-sectional view showing the cross-sectional view of (a) taken along the Z-X plane.

[0058] Battery 10c includes a closure member 12c. The closure member 12c has the same shape as that shown in FIG. 1, the diameter of the intermediate member 20b matches the diameter of the cylindrical portion 31, and the thickness of the intermediate member 20b is thinner on the outer periphery than on the inner periphery. This provides the same advantages as battery 10b, and also improves melting efficiency compared to when using closure member 12 because the laser irradiated portion of the intermediate member 20b is thinner when joining the ring portion 21, intermediate member 20b, and battery can 11. On the other hand, a disadvantage is that the intermediate member 20b in FIG. 6 has a more complex shape than the intermediate member 20 in FIG. 1 and the intermediate member 20a in FIG. 5, resulting in higher costs.

[0059] In this structure, it is not necessary to bond the intermediate member to the battery can, but it is sufficient that the sealing member 12c and the battery can 11 are bonded.

[0060] In the present disclosure, the shape of the battery can 11 is cylindrical, but the shape of the battery can 11 is not limited to this. For example, the shape of the battery can 11 may be an elliptical cylinder or a polygonal cylinder.

[0061] In the present disclosure, the shape of the sealing member 12 is a disk shape with the outer periphery protruding higher than the central portion, but the shape of the sealing member 12 is not limited to this, and it may have any shape as long as it can be inserted inside the opening edge portion of the battery can 11 so that its outer surface faces the inner surface of the opening edge portion 17 and can seal the opening edge portion 17.

[0062] The configuration of the present disclosure may also be effective when multiple batteries are electrically connected using current collector plates or the like to form a battery module. Currently, battery modules require current collector plates above and below the battery because the positive electrodes of the batteries are electrically connected to a sealing material and the negative electrodes to the bottom of the can. As in JP 2021-93381 A, some efforts have been made to reduce the required volume of the battery module and improve the volumetric energy density by concentrating the current collectors on the upper side.

[0063] Consider the case where current collector plates are connected by welding. Current collector plates are often made of low-resistance metals such as copper or aluminum. In cylindrical secondary batteries, the sealing member, which serves as the positive electrode, is often made of aluminum, and the can is made of iron. In this case, welding is difficult because dissimilar materials, such as aluminum or copper, are welded to iron. On the other hand, in this configuration, a metal with high thermal conductivity, such as aluminum or copper, is joined to the sealing member. If the metal to be joined to the sealing member and the busbar member that electrically connects the battery are selected to be of the same material, it is possible to perform like-material welding when fabricating a battery module. This simplifies welding for EV manufacturers and other parties who purchase batteries and assemble battery modules.

[0064] However, even when joining a metal material with a melting point lower than that of the sealing material to the top surface of the sealing material, as mentioned above, the welding becomes dissimilar welding, which raises the difficulty of welding. In particular, to achieve sufficient heat dissipation, it is necessary to use metal materials with significantly different melting points, such as aluminum or copper, instead of iron, which is the material of the sealing material. When joining dissimilar materials, depending on the combination of metal materials, a brittle layer called an intermetallic compound layer can form in the joint. Due to the influence of the intermetallic compound layer, it is difficult to achieve sufficient joint strength when joining a metal material to the top surface of the sealing material.

[0065] An intermetallic compound layer generally occurs when metals with different melting points are mixed together. When joining a metal material to a sealing material, for example by welding, the metal material and the sealing material are generally brought into close contact with each other and heat is applied from the metal material side to perform welding. In this case, heat is applied from the low-melting-point metal side, so most of the metal on the low-melting-point side becomes molten first during welding. In this case, when the high-melting-point metal material melts with a delay, it mixes with the metal on the low-melting point side, generating an intermetallic compound and reducing the joint strength of the weld.

[0066] In order to obtain sufficient joint strength when joining dissimilar materials with significantly different melting points, it is important to process from the high-melting-point metal material side. To achieve this, this configuration proposes a method for joining dissimilar materials in the process of manufacturing the sealing material.

[0067] In addition, the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example.

[0068] The battery according to the present disclosure can be used in various can-type batteries, and is useful for applications such as power sources for portable devices, hybrid vehicles, electric vehicles, etc.

[0069] 10, 10a, 10b, 10c Battery 11 Battery can 12, 12a, 12b, 12c Sealing material 14 Electrolyte 15 Electrode body 16 Melting laser 17 Opening edge 18 Same material fusion zone 20, 20a, 20b Intermediate member 21 Ring portion 22 Gasket portion 23 Disk portion 25 Welding laser 26 Dissimilar material fusion zone 27 Surface fusion width 28 Interface fusion width 29 Gasket compression length 31 Cylindrical portion 32 Bottom portion

Claims

1. a metal battery can having a cylindrical portion with an open edge at one end and a bottom portion closing the other end of the cylindrical portion; An electrode body accommodated inside the cylindrical portion; a sealing member joined to the opening edge portion of the battery can and sealing the opening of the opening edge portion, The sealing member is A gasket portion, A metal disk portion; a ring portion having the disk portion crimped at the center thereof via the gasket portion; An intermediate member joined to the upper surface of the ring portion, battery.

2. the intermediate member is made of a metal material having a melting point lower than the melting points of the metal of the disk portion and the metal of the battery can; 10. The battery of claim 1.

3. The sealing member is formed by joining the ring portion and the intermediate member by a first fusion zone.

10. The battery of claim 1.

4. the first fusion zone has a fusion area at a contact surface between the ring portion and the gasket portion that is larger than a fusion area at an interface between the ring portion and the intermediate member; 4. The battery of claim 3.

5. The first fusion zone is protruding toward the gasket portion on a surface where the ring portion and the gasket portion contact each other.

4. The battery of claim 3.

6. The ring portion has a recess on an upper surface thereof, and the intermediate member is joined to the ring portion so as to engage with the recess. The battery of any one of claims 1 to 5.

7. The intermediate member has a circular ring shape, and the diameter of the circular ring shape is the same as the diameter of the battery can. The battery of any one of claims 1 to 5.

8. The intermediate member has an outer circumferential thickness smaller than an inner circumferential thickness in the annular shape.

8. The battery of claim 7.