Battery case, battery, and method for manufacturing a battery case

Abstract

The present invention provides a battery case with suppressed thermal deformation, a battery, and a method for manufacturing a battery case. [Solution] A battery case according to one aspect of the present disclosure comprises a cylindrical body made of a bent metal plate and a pair of lids that seal the openings at both ends of the body, wherein the first end of the metal plate has one or more folded portions extending from one lid to the other lid and provided on the outer surface of the body, and a base portion which is a region overlapping with the folded portions, the second end of the metal plate overlapping the folded portions on the outer surface of the body, the body has a weld metal that extends from one lid to the other lid and joins the folded portions and the second end to each other, and the base portion has a heat-affected zone.

Description

Technical Field

[0001] The present disclosure relates to a battery case, a battery, and a method for manufacturing a battery case.

Background Art

[0002] In order to ensure the driving range of an electric vehicle, it is necessary to mount a large number of secondary batteries on the electric vehicle. A general secondary battery is installed such that its electrode terminals are arranged upward. Such a battery is called an upper-terminal type battery. However, when a plurality of upper-terminal type batteries are arranged in the floor portion of an electric vehicle, the thickness of the floor portion increases. As a result, the floor surface of the electric vehicle becomes higher, and it may become difficult for passengers to board the electric vehicle.

[0003] Due to the above circumstances, a side-terminal type battery may be adopted as a secondary battery for an electric vehicle. A side-terminal type battery is a battery installed such that its electrode terminals are arranged horizontally. An example of a side-terminal type battery is a long plate-shaped rectangular battery such as a blade battery. A rectangular battery means a battery whose exterior material has a substantially rectangular parallelepiped shape.

[0004] In the present disclosure, a blade battery means a long plate-shaped rectangular battery having an exterior material including a cylindrical body and a pair of lid bodies that seal the openings at both ends thereof, and electrodes are provided on the lid bodies. Hereinafter, for convenience of explanation, the direction from one lid body of the blade battery to the other lid body is referred to as the longitudinal direction, the direction perpendicular to the longitudinal direction and parallel to the long side of the lid body is referred to as the width direction, and the direction perpendicular to the longitudinal direction and the width direction is referred to as the thickness direction. The blade battery has a length in the longitudinal direction that is extremely long with respect to the width direction, and a length in the thickness direction that is extremely short with respect to the width direction.

[0005] The cover of a blade battery mounted on an electric vehicle, where the terminals are located, is oriented laterally. For this reason, blade batteries are called lateral terminal batteries. The longitudinal direction of a blade battery mounted on an electric vehicle often coincides with the vehicle's width, and the width often coincides with the vehicle's height. In this case, the dimensions along the longitudinal direction of the blade battery correspond to the vehicle's width, and the dimensions along the width correspond to the thickness of the vehicle's floor.

[0006] The longitudinal dimension of a blade battery, i.e., the distance between a pair of covers, can exceed 900 mm. Manufacturing such a long body by deep drawing is difficult. Therefore, the body of a battery case for a rectangular battery with horizontal terminals is usually manufactured by bending a metal sheet into a cylindrical shape and joining its ends. Examples of joining methods include seam welding and butt laser welding. Methods for joining the ends of metal sheets are disclosed, for example, in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 59-179284 [Patent Document 2] Japanese Patent Application Publication No. 07-309138 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] To ensure optimal performance of a rechargeable battery, it is necessary to maintain it within an appropriate temperature range. For example, a suitable temperature range for rechargeable batteries used in electric vehicles is 5 to 45°C. If the temperature of the rechargeable battery is too low, its internal resistance may increase, potentially reducing its capacity. Conversely, if the temperature is too high, the battery may deteriorate more rapidly.

[0009] Therefore, electric vehicles are equipped with a cooling mechanism for the secondary batteries. One example of a cooling method is to place the battery 2 on a cooling plate 3 through which a refrigerant is circulated, as shown in Figure 16. Another example of a cooling method is to place the cooling plate 3 between the batteries 2 arranged in a row, as shown in Figure 17.

[0010] In addition, a filler 4 may be placed in the gap between the battery 2 and the cooling plate 3. The filler 4 is a resin-based material called a thermal conductive resin or gap filler. The filler 4 reduces the thermal resistance between the battery 2 and the cooling plate 3, thereby promoting the cooling of the battery 2.

[0011] If the gap between the battery 2 and the cooling plate 3 is large, the cooling performance of the cooling plate 3 will decrease, or the amount of filler 4 used will increase. An increase in the amount of filler 4 used will lead to an increase in vehicle weight and an increase in vehicle manufacturing costs.

[0012] The battery cell with horizontal terminals has a large length along the vehicle width direction W. The inventors focused on the fact that thermal deformation perpendicular to the vehicle width direction W is likely to occur during welding of the body.

[0013] In view of the above-mentioned problems, this disclosure aims to provide a battery case in which thermal deformation is suppressed, a battery, and a method for manufacturing a battery case. [Means for solving the problem]

[0014] The gist of this disclosure is as follows:

[0015] (1) A battery case according to one aspect of the present disclosure comprises a cylindrical body made of a bent metal plate and a pair of lids that seal openings at both ends of the body, wherein the first end of the metal plate has one or more folded portions extending from one of the lids to the other lid and provided on the outer surface of the body, and a base portion which is a region overlapping with the folded portions, the second end of the metal plate overlapping the folded portions on the outer surface of the body, the body has a weld metal that extends from one of the lids to the other lid and joins the folded portions and the second end to each other, and the base portion has a heat-affected zone. (2) Preferably, in the battery case described in (1) above, the thickness of the metal plate is 0.1 to 1.4 mm. (3) Preferably, in the battery case described in (1) or (2) above, the metal plate is a nickel-plated steel plate having a base steel plate and a nickel-plated layer provided on the surface of the base steel plate. (4) Preferably, in the battery case described in (3) above, the thickness of the Ni-based plating layer is 0.1 to 10 μm. (5) Preferably, in the battery case described in any one of the above items (1) to (4), the weld metal is seam weld metal or laser weld metal. (6) Preferably, in the battery case described in any one of the above items (1) to (5), the weld metal is the laser weld metal, and the laser weld metal is separated from the inner surface of the battery case. (7) Preferably, in the battery case described in any one of the above items (1) to (6), the joint between the lid and the body is made of crimped or laser-welded metal. (8) Preferably, in the battery case described in any one of the above items (1) to (7), the lid is made of Ni-plated steel sheet or stainless steel sheet. (9) Preferably, in the battery case described in any one of the above items (1) to (8), the distance between the pair of lids is 1.5 times or more the length of the long side of the lid. (10) Preferably, in the battery case described in any one of the above items (1) to (9), the weld metal is arranged on the end face of the folded portion and the end face of the second portion.

[0016] (11) A battery according to another aspect of the present disclosure comprises a battery case as described in any one of paragraphs (1) to (10) above. (12) Preferably, in the battery described in (11) above, the battery case is electrically insulated from the electrodes.

[0017] (13) A method for manufacturing a battery case is a method for manufacturing a battery case as described in any one of (1) to (10) above, comprising the steps of: folding back the first end of a metal plate to form a folded portion and a base; bending the metal plate so that the folded portion is positioned on the outer surface of the body, overlapping the folded portion and the second end of the metal plate to form a cylindrical body; overlapping and welding the folded portion and the second end to form weld metal; and joining a lid to the openings at both ends of the body. (14) In the method for manufacturing a battery case described in (13) above, the cylindrical body is rectangular. (15) Preferably, in the method for manufacturing a battery case described in (13) above, the cylindrical body is cylindrical, and the manufacturing method further comprises a step of deforming the cylindrical body into a rectangular tubular shape before joining the lid to the openings at both ends of the body. (16) Preferably, in the method for manufacturing a battery case described in any one of the above items (13) to (15), the overlap welding is performed as seam welding, and when seam welding the metal plate, the base of the first end, the folded portion of the first end, and the second end are held between a pair of electrodes. (17) Preferably, in the method for manufacturing a battery case described in any one of the above items (13) to (16), the overlap welding is performed by laser welding, and when laser welding the metal plate, the penetration depth is made smaller than the sum of the thickness of the base of the first end, the folded portion of the first end, and the second end. [Effects of the Invention]

[0018] According to the present disclosure, a battery case with suppressed thermal deformation, a battery, and a method for manufacturing the battery case can be provided.

Brief Description of the Drawings

[0019] [Figure 1] It is a perspective view of the battery case according to this embodiment. [Figure 2] It is a sectional view taken along the line II-II of the joint provided on the body of the battery case of FIG. 1. [Figure 3] It is a sectional view of another aspect of the joint. [Figure 4] It is a sectional view of another aspect of the joint. [Figure 5] It is a sectional view of another aspect of the joint. [Figure 6] It is a sectional view of the seam welded portion of the body of a conventional battery case. [Figure 7] It is a sectional view of the butt laser welded portion of the body of a conventional battery case. [Figure 8] It is a sectional view of a joint manufactured by end face welding. [Figure 9] It is a schematic view of the process of bending the first end portion of a metal plate. [Figure 10] It is a schematic view of the process of bending a metal plate into a square tube shape. [Figure 11] It is a schematic view of the process of bending a metal plate into a cylindrical shape. [Figure 12] It is a schematic view of the process of manufacturing a body using two metal plates. [Figure 13] It is a schematic view of the process of seam welding the folded-back portion. [Figure 14] It is a schematic view of the process of seam welding the folded-back portion. [Figure 15] It is a schematic view of the process of laser welding the folded-back portion. [Figure 16] It is a schematic view of a battery provided with a cooling mechanism. [Figure 17] It is a schematic view of a battery provided with a cooling mechanism.

Modes for Carrying Out the Invention

[0020] The following description will explain, with reference to the drawings, a battery case and its manufacturing method according to embodiments of this disclosure, as well as the battery itself. The embodiments described below are general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the sequence of manufacturing processes shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, dimensions and other specifications in the drawings are not strictly illustrated.

[0021] (1. Battery case 1) The battery case 1 according to this embodiment is an exterior material for a battery 2. The type of battery 2 is not particularly limited. For example, it is preferable to use the battery case 1 according to this disclosure as an exterior material for a lithium-ion battery.

[0022] In recent electric vehicles, long, plate-shaped batteries with horizontal terminals, such as blade batteries, are sometimes used. Multiple horizontal-terminal batteries (batteries 2) mounted in an electric vehicle are stacked in the thickness direction with their longitudinal direction oriented in the vehicle width direction W, as illustrated in Figures 16 and 17. The battery case 1 according to this disclosure can be suitably used as an exterior material for horizontal-terminal batteries.

[0023] The battery case 1 according to this embodiment comprises a cylindrical body 11 made of a bent metal plate 112, and a pair of lids 12 that seal the openings at both ends of the body 11. The first end 1121 of the metal plate 112 extends from one lid 12 to the other lid 12 and is provided on the outer surface 14 of the body 11, and has one or more folded portions 1121F and a base portion 1121B which is a region overlapping with the folded portions 1121F. The second end 1122 of the metal plate 112 is superimposed on the folded portions 1121F on the outer surface 14 of the body 11. The body 11 extends from one lid 12 to the other lid 12 and has weld metal that joins the folded portions 1121F and the second end 1122 to each other. The base portion 1121B has a heat-affected zone H.

[0024] Figure 1 shows a perspective view of an example of the battery case 1 according to this embodiment. Figure 2 shows a cross-sectional view of the battery case 1 of Figure 1 along line II-II. Figure 2 is an enlarged cross-sectional view of the folded portion 1121F provided on the body 11. Figures 3 to 5 are enlarged cross-sectional views illustrating another aspect of the folded portion 1121F. Hereinafter, the details of the battery case 1 according to this embodiment will be described with reference to Figures 1, 2 and 3, etc.

[0025] (Body 11 and lid 12) The battery case 1 has a body 11 and a lid 12. The body 11 and the lid 12 are joined together to form the battery case.

[0026] The body 11 has a hollow, elongated structure with openings at both ends. That is, the body 11 is cylindrical and has openings at both ends in the longitudinal direction. The term "cylindrical" includes both cylindrical and rectangular shapes. When the battery case 1 is used as an exterior material for the battery 2 of an electric vehicle, it is preferable that the body 11 be rectangular.

[0027] The openings at both ends of the body 11 are sealed by a pair of plate-shaped covers 12. The ends of the body 11 and the ends of the covers 12 are joined by any means. Examples of means for joining the body 11 and the covers 12 are crimping and laser welding. In this embodiment of the battery case 1, the weld metal that joins the body 11 and the covers 12 is referred to as the second weld metal 13.

[0028] The cylindrical body 11 is made from bent metal plates 112. From the viewpoint of simplifying the manufacturing process, it is preferable that the body 11 be made from a single metal plate 112, as shown in Figure 1. On the other hand, the cylindrical body 11 can also be made from two or more metal plates 112. For example, the body 11 can be manufactured by joining two or more metal plates 112 and bending them into a cylindrical shape. Alternatively, the body 11 can be manufactured by joining two or more bent metal plates to form a cylindrical body.

[0029] Figure 12 shows a schematic diagram of the process of manufacturing the fuselage 11 by joining two bent metal plates. In the example shown in Figure 12, two metal plates bent into a U shape are overlapped at their ends to form a cylindrical body. By joining the two overlapping portions in the example shown in Figure 12, a fuselage 11 having two joint portions 111 is obtained. When the cylindrical fuselage 11 is made up of two or more metal plates 112, it is preferable that both of the two joint portions 111 have folded portions 1121F, which will be described later.

[0030] (Turning point 1121F) The bent metal plate 112 is joined at both ends to form a cylindrical shape. In the battery case 1 according to this embodiment, a folded portion 1121F is provided at one end of the metal plate 112. When the body 11 of the battery case is composed of two or more metal plates 112, a folded portion 1121F is provided at one end of each of the multiple metal plates 112. In this case, the body 11 has two or more folded portions.

[0031] The other end of the metal plate 112 is overlapped with the folded portion 1121F and joined to the folded portion 1121F. In this embodiment, the end of the metal plate 112 to which the folded portion 1121F is provided is referred to as the first end 1121 of the metal plate 112. The end of the metal plate 112 that overlaps with the folded portion 1121F is referred to as the second end 1122 of the metal plate 112. Furthermore, the region of the first end 1121 of the metal plate 112 that overlaps with the folded portion 1121F is referred to as the base 1121B.

[0032] The folded portion 1121F and the second end portion 1122 are welded together in an overlapping state. The folded portion 1121F, the second end portion 1122, and the weld metal joining them form a lap joint.

[0033] In this embodiment of the battery case 1, the weld metal joining the folded portion 1121F and the second end portion 1122 is referred to as the first weld metal. The first weld metal is distinct from the second weld metal 13 that joins the lid 12 and the body 11 as described above. Hereinafter, the term "weld metal" means "first weld metal." Hereinafter, the term "joint portion 111" means the first weld metal, and the overlap joint formed by the folded portion 1121F and the second end portion 1122 on which the first weld metal is provided.

[0034] The second end portion 1122 of the metal plate 112 is superimposed on the folded portion 1121F on the outer surface 14 of the body 11. Therefore, both the folded portion 1121F and the second end portion 1122 are located on the outer surface 14 of the battery case 1.

[0035] The joint 111 functions as a seam in the cylindrical body 11. Therefore, the folded portion 1121F that constitutes the joint 111 extends from one opening of the cylindrical body 11 to the other opening. As described above, the opening of the body 11 is provided with a cover 12 that seals it. Therefore, the folded portion 1121F extends from one cover 12 to the other cover 12.

[0036] As illustrated in Figure 1, when the fuselage 11 is made from a single metal plate 112, there is one joint 111 provided on the fuselage 11. On the other hand, when the fuselage 11 is made from two or more metal plates 112, the fuselage 11 may be provided with two or more joints 111. In this case, the fuselage 11 will have two or more folded portions 1121F.

[0037] (Weld metal (first weld metal)) The body 11 has a first weld metal that joins the overlapping folded portion 1121F and the second end portion 1122 to each other. The weld metal is formed along the extending direction of the folded portion 1121F. Thus, the first weld metal extends from one cover 12 to the other cover 12, similar to the folded portion 1121F.

[0038] An example of the first weld metal is the seam weld metal 1111S illustrated in Figures 2 and 3. The seam weld metal 1111S is formed by seam welding. Seam welding is a type of resistance welding in which pressure and current are applied to the base metal using a disc electrode 5, and the welding is performed continuously along the joint while rotating the electrode (see JIS Z 3001-6:2013 "Welding terminology - Part 6: Resistance welding").

[0039] The seam weld metal 1111S is formed inside the lap joint, as schematically shown in the cross-sectional views of Figures 2 and 3. The seam weld metal 1111S cannot be seen from the outside of the joint 111 joined by seam welding. However, indentations 1111i are formed where the seam weld metal 1111S is provided. Indentations 1111i are depressions on the surface of the base material caused by the disc electrode 5 as a result of welding in lap resistance welding (see JIS Z 3001-6:2013 "Welding Terminology - Part 6: Resistance Welding"). Indentations 1111i are formed on the surface of the second end portion 1122 facing the outside of the battery case 1, and on the surface of the base portion 1121B facing the inside of the battery case 1. Indentations 1111i are easily visible.

[0040] Another example of the first weld metal is the laser weld metal 1111L illustrated in Figures 4 and 5. The laser weld metal 1111L is formed by laser welding. Laser welding is a welding method that uses laser light as the energy medium (see JIS Z 3001-5:2013 "Welding Terminology - Part 5: Laser Welding"). Figure 3 shows a schematic cross-sectional view of the folded portion 1121F and the second end portion 1122 joined by laser welding. The laser weld metal 1111L is visible on the surface of the second end portion 1122.

[0041] The folded portion 1121F overlaps with the base portion 1121B at the first end portion 1121. Furthermore, the folded portion 1121F overlaps with the second end portion 1122. Therefore, three metal plates 112 are overlapped at the folded portion 1121F. The first weld metal joins at least the second end portion 1122 and the folded portion 1121F. The first weld metal may also extend to the base portion 1121B of the first end portion 1121. That is, the first weld metal may join the second end portion 1122, the folded portion 1121F, and the base portion 1121B. In Figures 2 and 4, the weld metal joins the second end portion 1122 and the folded portion 1121F, but is separated from the base portion 1121B of the first end portion 1121. The weld metal in Figures 3 and 5 joins the second end portion 1122, the folded portion 1121F, and the base portion 1121B.

[0042] (Heat affected zone H) A heat-affected zone (HAZ) H is formed around the first weld metal. The heat-affected zone H is defined as the portion of the unmelted metal plate 112 that has undergone changes in its structure, metallurgical properties, mechanical properties, etc., due to the heat of welding (see JIS Z 3001-1:2018 "Welding Terminology - Part 1: General"). In the battery case 1 according to this embodiment, the base portion 1121B of the first end portion 1121 has a heat-affected zone H.

[0043] In the battery case 1 according to this embodiment, as illustrated in Figures 3 and 5, if the weld metal extends to the base portion 1121B, the heat-affected zone H is naturally formed on the base portion 1121B. On the other hand, as illustrated in Figures 2 and 4, even if the weld metal does not extend to the base portion 1121B, the heat-affected zone H is provided on the base portion 1121B of the first end portion 1121. By welding the folded portion 1121F and the second end portion 1122 while the folded portion 1121F and the base portion 1121B are in contact, the heat-affected zone H is generated on the base portion 1121B.

[0044] (Effects and Benefits) Figures 6 and 7 show schematic cross-sectional diagrams of joints provided on the body of a conventional battery case. The joint in Figure 6 is formed by seam welding the end portion 613 of a metal plate without a folded portion. The joint in Figure 7 is formed by butt laser welding the end portion 613 of a metal plate without a folded portion. Joints like those shown in Figures 6 and 7 are easy to manufacture. Furthermore, joints like those shown in Figures 6 and 7 can flatten the outer surface 64 of the battery case. Therefore, these joints are widely used in conventional battery cases.

[0045] However, the inventors have found that conventional battery cases are prone to thermal deformation during welding. In particular, when the battery case is a blade battery with a large size along its longitudinal direction, the amount of thermal distortion in the direction perpendicular to the longitudinal direction of the body is large.

[0046] On the other hand, as illustrated in Figures 2 to 5, in the battery case 1 according to this embodiment, three metal plates 112 are stacked at the joint 111. Specifically, the joint 111 of the battery case 1 according to this embodiment has a base portion 1121B and a folded portion 1121F of the first end portion 1121 of the metal plate 112, and a second end portion 1122 of the metal plate 112. The joint 111 having such a configuration significantly improves the rigidity of the battery case 1 in the direction perpendicular to the longitudinal direction of the body 11. As a result, in the battery case 1 according to this embodiment, thermal strain in the direction perpendicular to the longitudinal direction of the body 11 is suppressed.

[0047] Furthermore, in the battery case 1 according to this embodiment, the heat-affected zone H is provided at the base portion 1121B of the first end portion 1121. This is because the joint portion 111 of the battery case 1 according to this embodiment is obtained by welding three metal plates 112 in a stacked state. Such a joint portion 111 can be manufactured in a short time. Therefore, the battery case 1 according to this embodiment is also excellent in terms of productivity.

[0048] The most basic embodiment of the battery case 1 according to this embodiment has been described above. A more preferred embodiment will be described below.

[0049] (Thickness and type of metal plate 112) The thickness of the metal plate 112 is not particularly limited. A preferred thickness for the metal plate 112 is 0.1 to 1.4 mm. The greater the thickness of the metal plate 112, the more the thermal distortion of the battery case 1 is suppressed. The smaller the thickness of the metal plate 112, the less weight the battery case 1 is reduced. The thickness of the metal plate 112 can be applied according to the application of the battery case 1 and the battery 2 having it. The thickness of the metal plate 112 may be 0.2 mm or more, 0.5 mm or more, or 0.8 mm or more. The thickness of the metal plate 112 may be 1.2 mm or less, 1.1 mm or less, or 1.0 mm or less. The thickness of the metal plate 112 can be measured on a flat surface using a micrometer or the like.

[0050] The material of the metal plate 112 can be an aluminum plate, a stainless steel plate, or a steel plate. From the viewpoint of improving the corrosion resistance of the battery case 1, aluminum plates and stainless steel plates are preferred. On the other hand, from the viewpoint of reducing the thickness of the metal plate 112 that constitutes the battery case 1 and making the battery case 1 lighter, it is preferable to use a steel plate, especially a high-strength steel plate, for the metal plate 112. When the metal plate 112 is a steel plate, it is preferable to use a nickel-plated steel plate. Nickel-plated steel plates have higher strength than aluminum plates and stainless steel plates, and corrosion resistance equal to or better than that of aluminum plates and stainless steel plates.

[0051] When the metal plate 112 is a nickel-plated steel plate, the battery case 1 according to this embodiment can also exhibit the effect of improving the corrosion resistance of the joint portion 111. This is because the joint portion 111 of the battery case 1 according to this embodiment has a configuration that excludes the end face 16 of the metal plate 112 from the inner surface 15 of the battery case 1.

[0052] Conventional battery cases are obtained by assembling materials cut from nickel-plated steel sheets. At the edges of materials cut from nickel-plated steel sheets, the nickel plating layer is substantially absent, and the underlying steel sheet is exposed. Therefore, while the surface of the nickel-plated steel sheet has high corrosion resistance, the edges have low corrosion resistance.

[0053] In the joint 611 of a conventional battery case manufactured by seam welding, as illustrated in Figure 6, the end face 66 of the Ni-plated steel sheet is exposed to the inner surface 65 of the battery case. The inner surface 65 of the battery case comes into contact with the electrolyte, which is a corrosive liquid filled in the battery case. The electrolyte corrodes the end face 66 of the Ni-plated steel sheet. Fe leaches from the end face 66 into the electrolyte. The Fe leached into the electrolyte degrades the performance of the battery.

[0054] However, as shown in Figures 2 to 4, in the battery case 1 according to this embodiment, the folded portion 1121F of the first end 1121 and the second end 1122 of the Ni-plated steel sheet are joined on the outer surface 14 of the body 11, i.e., outside the battery case 1. Therefore, both the end face 16 at the tip of the folded portion 1121F of the first end 1121 and the end face 16 at the tip of the second end 1122 are located outside the battery case 1. As a result, the end faces 16 of the Ni-plated steel sheet are separated from the inner surface 15 of the battery case 1. This improves the corrosion resistance of the joint 111 of the battery case 1.

[0055] Ni-plated steel sheets consist of a base steel sheet and a Ni-plating applied to the surface of the base steel sheet. The base steel sheet is preferably made of low-carbon aluminum-killed steel or IF steel (Interstitial Free Steel / ultra-low carbon steel). Specific examples of the chemical composition of the base steel sheet are as follows. The units for the elemental content shown below are in mass percent. (Example 1) Low carbon aluminum-killed steel C: 0.057, Si: 0.004, Mn: 0.29, P: 0.014, S: 0.007, Al: 0.050, Cu: 0.034, Ni: 0.021, remainder: iron and impurities. (Example 2) IF steel C: 0.004, Si: 0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.013, remainder: iron and impurities. (Example 3) IF steel C: 0.0012, Si: <0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.020, remainder: iron and impurities

[0056] A nickel-based plating layer is a plating layer whose main component is nickel, and which optionally contains alloying elements such as cobalt, feline, and crystalline wool. Furthermore, the amount of nickel deposited in a nickel-based plating layer is, for example, 2.6 to 35.6 g / m². 2 It can be within the range of

[0057] The combined thickness of the base steel sheet and the Ni-based plating layer is preferably 0.20 mm or more. A combined thickness of 0.20 mm or more allows for the achievement of both the mechanical strength and corrosion resistance required for the battery case 1. More preferably, the combined thickness of the base steel sheet and the Ni-based plating layer is 0.25 mm or more, and even more preferably 0.30 mm or more.

[0058] On the other hand, the total thickness of the base steel sheet and the Ni-based plating layer is preferably 1.40 mm or less. By having a total thickness of 1.40 mm or less, it is possible to achieve both the mechanical strength and corrosion resistance required for the battery case 1 while suppressing an increase in the mass of the lithium-ion battery. The total thickness of the base steel sheet and the Ni-based plating layer is more preferably 1.00 mm or less, and even more preferably 0.80 mm or less.

[0059] Here, the total thickness of the base steel plate and the Ni-based plating layer may be different for the body 11 and the lid 12 of the battery case 1. For example, the total thickness of the base steel plate and the Ni-based plating layer in the Ni-based plated steel plate used as the material for the body 11 may be thinner than the total thickness of the base steel plate and the Ni-based plating layer in the Ni-based plated steel plate used as the material for the lid 12.

[0060] Furthermore, in the Ni-plated steel sheet described above, the thickness of the Ni-plated layer is preferably 0.3 μm or more per side. A thickness of 0.3 μm or more of the Ni-plated layer per side makes it possible to further improve the corrosion resistance required for the battery case 1. The thickness of the Ni-plated layer per side is more preferably 1.0 μm or more, and even more preferably 1.2 μm or more.

[0061] On the other hand, the thickness of the Ni-based plating layer per side is preferably 10.0 μm or less. By making the thickness of the Ni-based plating layer per side 10.0 μm or less, it is possible to further improve the corrosion resistance required for the battery case 1 while suppressing an increase in manufacturing costs. The thickness of the Ni-based plating layer per side is more preferably 3.0 μm or less, and even more preferably 2.0 μm or less.

[0062] Furthermore, the thickness of the Ni-based plating layer may differ between the inner surface 15 and the outer surface 14 of the battery case 1. More specifically, the thickness of the Ni-based plating layer located on the inner surface 15 of the battery case 1 may be thinner than the thickness of the Ni-based plating layer located on the outer surface 14 of the battery case 1. In this case, from the viewpoint of ensuring corrosion resistance, it is preferable that the thickness of the Ni-based plating layer located on the inner surface 15 of the battery case 1 be 0.5 μm or more, and the thickness of the Ni-based plating layer located on the outer surface 14 of the battery case 1 be 1.0 μm or more.

[0063] The thickness of the Ni-based plating layer and the total thickness of the base steel sheet and the Ni-based plating layer can be determined by observing the cross-section of the Ni-based plating steel sheet using a scanning electron microscope (SEM) (for example, a JSM-7000F manufactured by JEOL Corporation). Specifically, a sample for cross-sectional observation is cut from the Ni-based plating steel sheet located at any part of the body 11 of the battery case 1 other than the joint 111. The cutting direction for obtaining the cross-section is the thickness direction of the Ni-based plating steel sheet. After polishing the obtained sample for cross-sectional observation, SEM images are taken at any five locations on the cross-section. The thickness of the Ni-based plating layer and the thickness of the base steel sheet measured in each obtained SEM image are averaged over the number of measurement locations, and the resulting average values ​​are taken as the thickness of the Ni-based plating layer and the thickness of the base steel sheet, respectively.

[0064] Furthermore, in the Ni-plated steel sheet described above, various chemical conversion coating layers (not shown) may be present between the base steel sheet and the Ni-plated layer. The presence of such chemical conversion coating layers makes it possible to further improve the adhesion between the base steel sheet and the Ni-plated layer. In addition, the presence of such chemical conversion coating layers makes it possible to further improve the corrosion resistance of the Ni-plated steel sheet.

[0065] The chemical conversion coating layer is not particularly limited and can be formed using various chemical conversion treatments. Examples of such chemical conversion treatments include chromate-based chemical conversion treatments and non-chromate-based chemical conversion treatments. Examples of non-chromate-based chemical conversion treatments include chemical conversion treatments using inorganic compounds such as vanadium compounds, titanium compounds, zirconium compounds, and phosphate compounds, as well as silica-based chemical conversion treatments.

[0066] The Ni-based plating layer of a Ni-plated steel sheet may be an alloyed plating layer that is alloyed with the underlying steel sheet. In this case, the Ni-based plating layer may be a fully diffused plating layer in which the Fe from the underlying steel sheet is diffused to its surface, or it may be a partially diffused plating layer in which the Fe from the underlying steel sheet is not diffused to its surface. On the other hand, the Ni-based plating layer may not be alloyed with the underlying steel sheet.

[0067] (Type and location of the first weld metal) As described above, preferred examples of the first weld metal are seam weld metal 1111S or laser weld metal 1111L. Examples of seam weld metal 1111S are shown in Figures 2 and 3. Examples of laser weld metal 1111L are shown in Figures 4 and 5. The shape of the seam weld metal 1111S and laser weld metal 1111L are not particularly limited. Various forms suitable for the material and thickness of the metal plate 112 can be applied to the first weld metal.

[0068] When the metal plate 112 is a Ni-plated steel plate and the first weld metal is laser weld metal 1111L, it is preferable that the laser weld metal 1111L is separated from the inner surface 15 of the battery case 1. That is, it is preferable that the penetration depth of the laser weld metal 1111L is less than the total thickness of the three metal plates 112 at the joint 111. The three metal plates 112 refer to the base portion 1121B and the folded portion 1121F of the first end portion 1121, and the second end portion 1122. This further enhances the corrosion resistance of the joint 111.

[0069] Similar to the end face 16 of the Ni-plated steel sheet, the surface of the laser-welded metal 1111L also lacks a Ni-plated layer. This is because, during laser welding, the Ni-plated layer melts and dissolves into the weld metal. The Ni dissolved in the weld metal slightly improves its corrosion resistance. Therefore, the corrosion resistance of the weld metal on the Ni-plated steel sheet is higher than that of the exposed base steel sheet on the end face 16. However, the corrosion resistance of the weld metal is lower than that of the Ni-plated layer. Consequently, the weld metal may also corrode in the electrolyte, potentially degrading the performance of the battery 2.

[0070] Unlike seam welding, laser welding can produce butt welded joints as illustrated in Figure 7. In butt welded joints, welding is performed with the end faces 66 of the base materials butted together. Therefore, by laser welding both ends 613 of the Ni-plated steel sheet as shown in Figure 7, the end faces 66 can be excluded from the inner surface 65 of the battery case 1. However, when butt laser welding is performed, the laser weld metal 6111L is exposed on the inner surface 65, reducing the corrosion resistance of the joint 611.

[0071] On the other hand, as shown in Figures 4 and 5, if the laser weld metal 1111L does not penetrate the joint 111, the weld metal is not exposed to the inner surface 15 of the battery case 1. This further improves the corrosion resistance of the joint 111 of the battery case 1, which is made of Ni-plated steel sheet.

[0072] (Means for joining the lid 12 and the body 11) One example of a suitable joining method between the lid 12 and the body 11 is welding. Therefore, the joint 111 between the lid 12 and the body 11 may be a second weld metal 13. Suitable examples of the second weld metal 13 are arc weld metal and laser weld metal 1111L. Alternatively, flanges can be provided at the ends of the lid 12 and the ends of the body 11, and these flanges can be overlapped and joined with seam weld metal 1111S.

[0073] Another example of a suitable joining method between the lid 12 and the body 11 is crimping. Crimping is widely used as a means of joining the can body and the lid. Crimping can also be applied to the battery case 1 according to this embodiment. Therefore, the joining portion 111 between the lid 12 and the body 11 may be a crimped portion.

[0074] (Material of lid 12) The lid 12 can be manufactured from any material that can be joined to the body 11. The lid 12 is, for example, a metal plate, preferably a nickel-plated steel plate, a stainless steel plate, or an aluminum plate. The nickel-plated steel plate exemplified as the material for the body 11 can also be used for the lid 12.

[0075] (External dimensions of battery case 1) The length along the body 11 of the battery case 1, i.e., the distance X between the pair of lids 12, is preferably 1.5 times or more the length Y of the longer side of the lid 12. If the lid 12 is rectangular, the longer side Y of the lid 12 is the length of the longer side. If the lid 12 is square, the longer side Y of the lid 12 is the length of one side of the square. A battery case 1 having such a shape can be suitably used as a blade battery.

[0076] Furthermore, the distance X between the pair of lids 12 of the battery case 1 is preferably, for example, 100 mm to 1500 mm, and more preferably 200 mm to 400 mm. The long side Y of the lid 12 is preferably, for example, 50 mm to 150 mm, and more preferably 90 mm to 120 mm. The short side Z of the lid 12 is preferably, for example, 10 mm to 50 mm, and more preferably 20 mm to 40 mm. The short side Z of the lid 12 is the length of the shorter side of the lid 12.

[0077] (edge ​​welding) The first weld metal may be placed on the end face of the folded portion 1121F and the end face of the second end portion 1122. In this case, the folded portion 1121F and the second end portion 1122 included in the joint 111 of the body 11 are edge-welded as shown in Figure 8 to form an edge joint. In JIS Z 3001-1:2018, an edge joint is defined as "a joint in which the end faces of two parts are joined at an angle of 0°≦α≦30°". This provides the effect of improving the corrosion resistance of the outer surface 14.

[0078] (3.Battery 2) A battery 2 according to another aspect of the present disclosure has a battery case according to this embodiment. The battery case is the outer casing of the battery 2. The battery 2 further includes an electrode body housed inside the battery case, positive and negative current collectors electrically connected to the electrode body, and an electrolyte. One lid of the battery case is provided with electrode terminals electrically connected to the current collectors. The lid is provided with an electrolyte injection port and an injection plug to seal the injection port. The lid is also provided with a cleavage valve port and a cleavage valve to seal the cleavage valve port. The cleavage valve port cleaves open when the pressure inside the battery case increases due to some abnormality, releasing the pressure inside the battery case.

[0079] In the battery 2 according to this embodiment, thermal strain in the direction perpendicular to the longitudinal direction of the battery case is suppressed. Furthermore, the battery 2 according to this embodiment has high productivity.

[0080] In the battery 2 according to this embodiment, the battery case is preferably a neutral can. A neutral can is a battery case that is electrically insulated from the electrodes. The neutral can is electrically neutral.

[0081] Preferably, electrodes are arranged on the lid 12 of the battery case 1. By using a battery 2 with electrodes arranged on the lid 12 as the battery 2 of an electric vehicle, the thickness of the electric vehicle's floor can be reduced, and the passenger space of the electric vehicle can be expanded.

[0082] The battery 2 according to this embodiment may be a battery cell. A battery cell is the smallest unit of a battery in a battery module. A battery module is constructed by electrically connecting multiple battery cells. Multiple battery modules can be further electrically connected to form a battery pack. A battery pack can also be constructed by electrically connecting a large number of battery cells without constructing a battery module. A battery module or battery pack can be used, for example, as a power source for an electric vehicle. However, it is not essential to use a battery module or battery pack in an electric vehicle. It is also possible to mount a large number of battery cells in an electric vehicle without constructing a module or pack.

[0083] (4. Manufacturing method of battery case 1) A method for manufacturing a battery case 1 according to another aspect of the present disclosure is a method for manufacturing a battery case according to the above embodiment, comprising the steps of: folding back the first end portion 1121 of a metal plate 112 to form a folded portion 1121F and a base portion 1121B; bending the metal plate 112 so that the folded portion 1121F is positioned on the outer surface 14 of the body 11, overlapping the folded portion 1121F and the second end portion 1122 of the metal plate 112 to form a cylindrical body; overlapping and welding the folded portion 1121F and the second end portion 1122 to form weld metal; and joining a lid 12 to openings at both ends of the body 11.

[0084] The manufacturing method of the battery case 1 according to this embodiment will be described below. Naturally, the preferred embodiments of the battery case 1, battery case, and battery 2 described above can also be applied to the manufacturing method of the battery case 1.

[0085] (Step S1: Fold back the first end 1121) First, as illustrated in Figure 9, the first end portion 1121 of the metal plate 112 is folded back to form a folded portion 1121F and a base portion 1121B. The folded portion 1121F extends from the location where one cover 12 is provided to the location where the other cover 12 is provided. The first end portion 1121 of the metal plate 112 is also folded back toward the surface used as the outer surface 14 of the body 11.

[0086] (Step S2: Bending the metal plate 112) Next, the metal plate 112 is bent to form a cylindrical body. At this time, the folded portion 1121F is positioned on the outer surface 14 of the body 11. Then, the folded portion 1121F and the second end 1122 of the metal plate 112 are overlapped.

[0087] In the process of bending the metal plate 112, the cross-sectional shape of the cylinder may be made to match the cross-sectional shape of the body 11 of the battery case 1 that is ultimately obtained. For example, if the body 11 of the battery case 1 is to be rectangular, it is preferable to bend the metal plate 112 into a rectangular shape, as illustrated in Figure 10.

[0088] On the other hand, in the process of bending the metal plate 112, the cross-sectional shape of the cylinder may be made different from the cross-sectional shape of the body 11 of the battery case 1 that is ultimately obtained. In this case, after welding the folded portion 1121F and the second end portion 1122, which will be described later, and before joining the body 11 and the lid 12, the cylindrical body 11 is deformed to match the shape of the body 11 of the battery case 1 that is ultimately obtained. The process of deforming the body 11 is sometimes referred to as the tube expansion process. In this disclosure as well, for convenience, the process of deforming the cross-sectional shape of the cylindrical body will be referred to as the tube expansion process. In the tube expansion process, the cross-sectional area of ​​the cylindrical body may be increased or decreased. For example, if the cross-section of the cylindrical body is deformed from a circle to a rectangle, the cross-sectional area may decrease. Such an action is also referred to as the tube expansion process.

[0089] If the manufacturing method of the battery case 1 includes a tube expansion step, it is preferable to bend the metal plate 112 into a cylindrical shape, as shown in Figure 11, for example. In the tube expansion step, the metal plate 112 that forms the cylinder can be deformed into a rectangular tube, as illustrated in Figure 10, for example.

[0090] In Figures 10 and 11, there is only one metal plate, but as illustrated in Figure 12, the body 11 may be constructed using two or more metal plates. In the example shown in Figure 12, each of the two metal plates is bent into a U-shape. On the left side of the paper, one metal plate has folded-over portions 1121F at both ends. On the right side of the paper, the other metal plate does not have folded-over portions 1121F at both ends. The metal plate on the left side of the paper has first end portions 1121 at both ends, and the metal plate on the right side of the paper has second end portions 1122 at both ends. By overlapping the folded-over portions 1121F and the second end portions 1122 of the two metal plates, a cylindrical body can be formed.

[0091] Alternatively, one could first join multiple metal plates to form a single flat plate having a joint portion 111, and then bend this into a cylindrical shape to form a cylindrical body.

[0092] (Step S3: Overlapping and welding of the folded portion 1121F and the second end portion 1122) Next, the overlapping folded portion 1121F and the second end portion 1122 are welded together. This forms the fuselage 11. The welding is performed along the extending direction of the folded portion 1121F, from one opening of the fuselage 11 toward the other opening. The welding forms a first weld metal that joins the overlapping folded portion 1121F and the second end portion 1122 together.

[0093] (Seam welding) One example of a welding method is seam welding. Figure 13 shows a schematic perspective view of the folded portion 1121F and the second end portion 1122 to be seam welded. Figure 14 shows a schematic cross-sectional view of the folded portion 1121F and the second end portion 1122 to be seam welded. In seam welding, a pair of disc electrodes 5 are used to apply pressure and current to the base portion 1121B of the first end portion 1121, the folded portion 1121F, and the second end portion 1122. While rotating the disc electrodes 5, resistance welding is performed continuously along the folded portion 1121F to the folded portion 1121F and the second end portion 1122.

[0094] During seam welding, the base portion 1121B and folded portion 1121F of the first end portion 1121, and the second end portion 1122 are clamped between a pair of disc electrodes 5. This improves the efficiency of joining the first end portion 1121 and the second end portion 1122 of the metal plate 112.

[0095] During seam welding, heat preferentially occurs at the overlapping surface of the folded portion 1121F of the first end 1121 and the second end 1122, forming a nugget. The reason for this is as follows: The current path between the base 1121B of the first end 1121 and the folded portion 1121F of the first end 1121 is (1) the contact area created by the pressure of the disc electrode 5, and (2) the bend between the folded portion 1121F and the base 1121B. On the other hand, the current path between the folded portion 1121F of the first end 1121 and the second end 1122 is (1) only the contact area created by the pressure of the disc electrode 5. Therefore, current concentrates at the contact area between the folded portion 1121F of the first end 1121 and the second end 1122, and its temperature rises easily. On the other hand, the temperature does not rise easily at the contact points between the base portion 1121B of the first end portion 1121 and the folded portion 1121F of the first end portion 1121.

[0096] For the reasons stated above, seam welding can easily form a weld metal that joins the folded portion 1121F of the first end 1121 and the second end 1122, but does not join the folded portion 1121F of the first end 1121 and the base 1121B. Alternatively, it is possible to select current conditions that can produce a weld metal that joins the base 1121B and folded portion 1121F of the first end 1121, as well as the second end 1122. However, in either case, a heat-affected zone H is formed at the base 1121B of the first end 1121.

[0097] Furthermore, in lap resistance welding such as seam welding, the contact area between the base metal and the electrode is less likely to melt than the overlapping surface of the base metal. This is because the temperature of the contact area does not rise easily due to heat transfer from the base metal to the electrode. In addition, if the molten metal extends to the outside of the base metal, the molten metal will scatter. This phenomenon is called spattering. In general seam welding, it is preferable to suppress spattering. Therefore, seam welding forms the weld metal by melting and solidifying only the inside of the base metal. When the first end 1121 and the second end 1122 are joined by seam welding, the weld metal is naturally separated from the inner surface 15 of the battery case 1.

[0098] The disc electrode 5 can be, for example, a flat electrode or an R-type electrode. A flat electrode is an electrode in which the portion in contact with the base material is straight in the cross-section along the central axis of the electrode. An R-type electrode is an electrode in which the portion in contact with the base material is rounded in the cross-section along the central axis of the electrode. An R-type electrode is preferable because it concentrates the current.

[0099] The tip radius (R) of the R electrode is preferably 3 or greater. The tip radius (R) refers to the radius of curvature of the portion that contacts the base material in the cross-section along the central axis of the electrode. By setting the tip radius (R) to 3 or greater, dust generation when the nugget becomes large can be suppressed.

[0100] To minimize the effects of electrode wear, seam welding may be replaced with wire seam welding. Wire seam welding is a type of seam welding in which a thin copper wire is belted around the circumference of a disc electrode, and this copper wire is used as the electrode.

[0101] Examples of preferred conditions for seam welding are as follows: • Diameter of disc electrode 5: Φ100~400mm • Width of disc electrode 5: 3-10 mm Welding speed: 2-20 m / min

[0102] Furthermore, it is preferable to cool the disc electrode. Cooling the disc electrode stabilizes the seam welding. For example, by circulating a coolant through the central axis to which the disc electrode is attached, seam welding can be performed while cooling the disc electrode.

[0103] In seam welding, nuggets may not be formed. If nuggets are not formed, the metal plates are pressure-welded. In the battery case manufacturing method according to this embodiment, seam welding without nugget formation is also permitted. In this disclosure, "seam-welded metal" is a concept that also includes the pressure-welded portion formed by seam welding.

[0104] (Laser welding) Another example of a welding method is laser welding. In laser welding, laser light is used as the energy medium to weld the folded portion 1121F and the second end portion 1122. The laser welding conditions can be appropriately determined according to the thickness of the metal plate 112, etc. Figure 15 shows a schematic cross-sectional view of the folded portion 1121F and the second end portion 1122 to be laser welded.

[0105] In laser welding, the laser L is irradiated onto the second end portion 1122. The penetration depth is made to be at least greater than the thickness of the second end portion 1122. This allows the second end portion 1122 and the folded portion 1121F of the first end portion 1121 that is superimposed on it to be joined. The penetration depth may also be greater than the sum of the thickness of the second end portion 1122 and the thickness of the folded portion 1121F of the first end portion 1121. This allows the second end portion 1122, the folded portion 1121F of the first end portion 1121, and the base portion 1121B of the first end portion 1121 to be joined. On the other hand, if the metal plate 112 is a Ni-plated steel plate, it is preferable to make the penetration depth smaller than the sum of the thickness of the base portion 1121B of the first end portion 1121, the folded portion 1121F of the first end portion 1121, and the second end portion 1122. This separates the laser-welded metal 1111L from the inner surface 15 of the battery case 1, thereby improving the corrosion resistance of the joint 111. The term "penetration depth" is defined as the thickness of the weld metal melted in the plate thickness direction, excluding the excess weld material (see JIS Z 3001-1:2018 "Welding Terminology - Part 1: General").

[0106] During laser welding, the second end portion 1122 and the folded portion 1121F and base portion 1121B of the first end portion 1121 are overlapped. As a result, a heat-affected zone H is formed at the base portion 1121B of the first end portion 1121.

[0107] Examples of laser welding conditions are shown below. • Focusing diameter: 0.1~0.8mm • Output: Adjusts according to plate thickness and welding speed to achieve the desired penetration depth. Welding speed: 2-30 m / min • Defocusing: If you want to reduce sputtering, you can defocus by about 1% of the focal length. • Shielding gas: Nitrogen or argon gas may be used to suppress temper color. Furthermore, the focusing shape may be changed using a DOE (diffraction grating), which may suppress sputtering.

[0108] (Step S4: Joining the lid 12 to the body 11) Finally, the lids 12 are joined to the openings at both ends of the body 11. This completes the battery case 1. One example of a method for attaching the lids 12 to the body 11 is crimping. Crimping is widely used in the manufacture of cans. Another example of a method for attaching the lids 12 to the body 11 is laser welding. In either case, the airtightness of the battery case 1 can be easily ensured.

[0109] The most basic aspects of the manufacturing method for the battery case 1 according to this embodiment have been described above. However, it should be noted that the manufacturing method for the battery case 1 according to this embodiment may have various additional steps. For example, the manufacturing method for the battery case 1 may further include a step of making through holes in the body 11 or the lid 12. Through holes include, for example, electrode insertion ports, opening valve ports, and liquid injection ports. If the body 11 is made up of two or more metal plates 112, the manufacturing method for the battery case 1 may include a step of joining the multiple metal plates 112 that make up the body 11 together.

[0110] Furthermore, in the manufacture of the battery 2 comprising the battery case 1, it should be noted that the assembly of the battery case 1 and the installation of the battery 2 components into the battery case 1 can be carried out in parallel. For example, if the through-hole is a liquid injection port, the electrolyte can be injected into the battery case 1 through the through-hole and then the through-hole can be sealed. Also, various components such as electrodes can be installed inside the battery case 1 before joining the lid 12 to the body 11. When the battery case comprising the battery case 1 is a neutral can, the manufacturing method of the battery case 1 according to this embodiment can be increased by adding the steps of forming electrode insertion ports in the body 11 or lid 12 of the battery case 1 and assembling insulating material into the electrode insertion ports. The insulating material electrically insulates the electrodes from the battery case 1. Any steps necessary for the manufacture of the battery 2 can be appropriately added to the manufacturing method of the battery case 1 according to this embodiment. [Explanation of Symbols]

[0111] 1 Battery case 11 Torso 111 Joint 1111S Seam Weld Metal 1111i Indentation 1111L Laser Welded Metal 112 Metal plate 1121 First end 1121F turnaround section 1121B base 1122 Second end 113 (End of a metal plate without a folded portion) 12 Lid 13 Second weld metal 14 Exterior 15. Inner self 16 End face 2 batteries 3 Cooling plate 4. Filler 5. Disc electrodes 611 Joint 6111S Seam Weld Metal 6111L Laser Welded Metal 613 (End of a metal plate without a folded portion) 64 Exterior 65 Inner self 66 End face L Laser H heat affected zone X Distance between a pair of lids Y is the length of the longer side of the lid. Z is the length of the shorter side of the lid.

Claims

1. A cylindrical body made of bent metal plates, A pair of covers that seal the openings at both ends of the body, A battery case equipped with, The first end of the metal plate has one or more folded portions extending from one of the lids to the other lid and provided on the outer surface of the body, and a base portion which is a region overlapping with the folded portions. The second end of the metal plate is superimposed on the folded portion on the outer surface of the body. The body has a weld metal that extends from one of the lids to the other lid and joins the folded portion and the second end to each other. The base has a heat-affected zone. Battery case.

2. The battery case according to claim 1, wherein the thickness of the metal plate is 0.1 to 1.4 mm.

3. The battery case according to claim 1, wherein the metal plate is a nickel-plated steel plate having a base steel plate and a nickel-plated layer provided on the surface of the base steel plate.

4. The battery case according to claim 3, wherein the thickness of the Ni-based plating layer is 0.1 to 10 μm.

5. The battery case according to any one of claims 1 to 4, wherein the weld metal is seam weld metal or laser weld metal.

6. The weld metal is the laser weld metal, The laser-welded metal is separated from the inner surface of the battery case. The battery case according to claim 5.

7. The battery case according to any one of claims 1 to 4, wherein the joint between the lid and the body is made of crimped or laser-welded metal.

8. The battery case according to any one of claims 1 to 4, wherein the cover is made of Ni-plated steel sheet or stainless steel sheet.

9. The battery case according to any one of claims 1 to 4, wherein the distance between the pair of lids is 1.5 times or more the length of the long side of the lids.

10. The battery case according to any one of claims 1 to 4, wherein the weld metal is arranged on the end face of the folded portion and the end face of the second end.

11. A battery comprising the battery case described in any one of claims 1 to 4.

12. The battery according to claim 11, wherein the battery case is electrically insulated from the electrodes.

13. A method for manufacturing a battery case according to any one of claims 1 to 4, A step of folding back the first end of a metal plate to form a folded portion and a base, The process involves bending the metal plate so that the folded portion is positioned on the outer surface of the body, overlapping the folded portion and the second end of the metal plate, and forming a cylindrical body. The process involves overlapping and welding the folded portion and the second end to form a weld metal, The process of joining the lid to the openings at both ends of the body, A method for manufacturing a battery case equipped with a battery case.

14. The method for manufacturing a battery case according to claim 13, characterized in that the cylindrical body is rectangular in shape.

15. The tubular body is cylindrical, The manufacturing method further comprises a step of deforming the cylindrical body into a rectangular tubular shape before joining the lids to the openings at both ends of the body. The method for manufacturing a battery case according to claim 13.

16. The aforementioned overlapping weld is a seam weld. The method for manufacturing a battery case according to claim 13, characterized in that when seam welding the metal plate, the base portion of the first end, the folded portion of the first end, and the second end are clamped by a pair of electrodes.

17. The aforementioned overlap welding is performed using laser welding. When laser welding the metal plate, the penetration depth is made smaller than the combined thickness of the base of the first end, the folded portion of the first end, and the second end. The method for manufacturing a battery case according to claim 13.

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