Secondary battery

Abstract

The present application relates to a secondary battery capable of improving construction efficiency. The secondary battery is provided with a power generation element and an outer package portion that houses the power generation element inside, the outer package portion having a cylindrical portion having opening portions in two opposing faces, inner covers disposed at each opening portion, and a first resin disposed so as to cover the faces of the inner covers on the opening portion side of each opening portion, the first resin being disposed so as to fill in between the cylindrical portion and the inner covers, the cylindrical portion and the inner covers being integrated by the first resin.

Description

Technical Field

[0001] This application relates to secondary batteries. Background Technology

[0002] Lithium-ion rechargeable batteries and other batteries are widely used as portable power sources for personal computers, portable terminals, and vehicle propulsion. As an example of a battery, a laminated battery is known. A laminated battery has a structure in which a power-generating element is sealed inside a laminated casing formed by overlapping film-like laminated sheets. Furthermore, the laminated battery has a sealing region formed by welding the edges of the laminated casing together, with terminals electrically connected to the power-generating element protruding outwards from the interior of the laminated casing. Thus, the power-generating element is sealed inside the laminated casing. Additionally, the laminated battery has a sealing region on the outside of the power-generating element formed by overlapping and welding laminated sheets.

[0003] Previously, miniaturization of battery structures has been studied. For example, Patent Document 1 discloses a technique for miniaturizing a laminated battery by bending the sealing region at the end.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-173900 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The technology in Patent Document 1 enables the miniaturization of laminated batteries, but further improvements in the efficiency of secondary battery construction are desired.

[0009] Miniaturization of laminated batteries can be achieved, for example, by shortening the width of the sealing area (sealing width) that holds the electrode terminals, but the sealing width usually needs to be set to a length exceeding 3 mm. This is due to the following reasons: (1) If the sealing width is short, proper heat fusion cannot be performed, resulting in poor sealing. (2) Due to the low rigidity of the laminated outer casing, if the sealing width is short, the adhesive in the sealing area may peel off due to external impacts, resulting in the adhesive surface not being maintained. (3) During heat fusion, if the terminals are not parallel to the adhesive surface of the laminated outer casing, a short sealing width weakens the corrective force to restore the tilt, thus increasing the probability of poor sealing due to improper heat fusion. (4) During heat fusion, if the sealing width is short, the pressure applied per unit area of ​​the sealing area by the heat fusion joint increases, and the metal layer inside the laminated outer casing may bite into the terminal through the insulating layer. If the metal layer bites into the terminal, it will cause a short circuit, which is undesirable. For the reasons mentioned above, it is difficult to shorten the sealing width to miniaturize laminated batteries.

[0010] Therefore, the purpose of this disclosure is to provide a secondary battery that can improve construction efficiency.

[0011] Methods for solving problems

[0012] As a solution to the above-mentioned problems, this disclosure provides a secondary battery having a power generation element and an outer casing that internally houses the power generation element. The outer casing has: a cylindrical portion having openings on two opposing sides, an inner cover disposed at each opening, and a first resin disposed to cover the opening sides of each opening and the inner cover. The first resin is disposed to fill the space between the cylindrical portion and the inner cover, and the cylindrical portion and the inner cover are integrated using the first resin.

[0013] The aforementioned secondary battery can also be configured as follows. That is, the secondary battery may further include electrode terminals connected to a power generation element, and the inner cover may have a surface disposed on the opening side of the cylindrical portion, a protrusion extending from the outer periphery of the surface toward the inner side of the cylindrical portion, and a space surrounded by the protrusion. At least one of the inner covers has a through hole on its surface, and the electrode terminals are disposed in a manner that penetrates the through hole. The first resin disposed on the inner cover side through which the electrode terminals penetrate is also disposed in a manner that covers at least a portion of the outer periphery of the electrode terminals and fills the space between the through hole and the electrode terminals. The cylindrical portion, the inner cover, and the electrode terminals are integrated using the first resin.

[0014] The aforementioned secondary battery can also be configured as follows: The outer casing may have a second resin filled inside it, and the cylindrical portion, inner cover, electrode terminals, and power generation element may be integrated using the second resin. Alternatively, the power generation element may be encapsulated by a resin film that provides insulation and water vapor barrier properties.

[0015] The aforementioned cylindrical portion can also be one of the following: That is, the cylindrical portion can be a cylindrical metal body or a metal laminate formed into a cylindrical shape. Alternatively, the cylindrical portion can be composed of two U-shaped metal plates that are inverted and overlapped, with the ends of the overlapping metal plates located on opposite sides of the cylindrical portion. The cylindrical portion has a third resin arranged to cover each side, and the ends of the overlapping metal plates are integrated using the third resin. Alternatively, the cylindrical portion can be composed of a single metal plate, with the ends of the overlapping metal plate located on one side of the cylindrical portion. The cylindrical portion has a third resin arranged to cover one side of the cylindrical portion, and the ends of the overlapping metal plates are integrated using the third resin.

[0016] Invention Effects

[0017] The secondary battery disclosed herein can improve structural efficiency. Attached Figure Description

[0018] Figure 1 This is a top view of a secondary battery 100.

[0019] Figure 2 Therefore Figure 1 Sectional view of section II-II.

[0020] Figure 3 This is a top view of an example of a secondary battery in which the positive terminal 31 and the negative terminal 32 are arranged to protrude from the same side in the width direction of the outer casing 20.

[0021] Figure 4 (a) is a top view of the cylindrical part 21. Figure 4 (b) is a cross-sectional view in the width direction. Figure 4 (c) is a side view of the cylindrical portion 21 as seen from the width direction.

[0022] Figure 5 (a) is a cross-sectional view near the opening 21a of the cylindrical portion 21, which has protrusions 21b at each end of the surface in the thickness direction. Figure 5 (b) is a cross-sectional view near the opening 21a of the cylindrical portion 21, which is provided with a protrusion 21b that bends inward.

[0023] Figure 6 (a) is a three-dimensional view of the inner cover 22. Figure 6 (b) is a sectional view cut from (a) by bb. Figure 6 (c) is a sectional view cut by (a) at cc.

[0024] Figure 7 (a) is a cross-sectional view of the inner cover 22 having a tapered (sloping) portion 22e. Figure 7(b) is an example of the use of the inner cover 22 with the cone 22e.

[0025] Figure 8 This is a diagram comparing the longitudinal cross-sectional views of a conventional laminated battery (a) and a secondary battery 100 (b).

[0026] Figure 9 This diagram compares top views of a conventional laminated battery (a) and a secondary battery 100 (b).

[0027] Figure 10 This is a cross-sectional view of the secondary battery 101 along its length.

[0028] Figure 11 This is a cross-sectional view of the secondary battery 102 along its length.

[0029] Figure 12 This is a top view of the power generation element 10, which is wrapped in resin film 13.

[0030] Figure 13 (a) is a top view of the cylindrical part 121. Figure 13 (b) is a cross-sectional view of the cylindrical portion 121 in the width direction.

[0031] Figure 14 (a) is a top view of the cylindrical part 221. Figure 14 (b) is a cross-sectional view of the cylindrical part 221 in the width direction.

[0032] Figure 15 This diagram illustrates one cooling method for a secondary battery that uses the cylindrical portion 221.

[0033] Explanation of reference numerals in the attached figures

[0034] 10 Power Generation Elements

[0035] 11, 12 Electrodes (Electrode Plates)

[0036] 13 Resin film

[0037] 20. Exterior Design Department

[0038] 21, 121, 122 cylindrical part

[0039] 21a Opening

[0040] 21b Protrusion

[0041] 21c hole

[0042] 21d hole

[0043] 22 Inner Lid

[0044] 22a face

[0045] 22b Protrusion

[0046] 22c space

[0047] 22d through hole

[0048] 22e Conical part

[0049] 22f hole

[0050] 23 First Resin

[0051] 24. Second Resin

[0052] 30 Electrode Terminals

[0053] 31 Positive extremes

[0054] 32 Negative extremes

[0055] 100, 101, 102 secondary batteries

[0056] 121a and 221a metal plates

[0057] 121b bottom surface

[0058] 121c Protrusion

[0059] 121d, 221c, third resin

[0060] 221b end Detailed Implementation

[0061] Regarding the secondary battery of this disclosure, the description will primarily use a secondary battery 100 as one embodiment.

[0062] Figure 1 The image shows a top view of the secondary battery 100. Figure 2 The middle shows Figure 1 A sectional view cut along section II-II. Here, in Figure 1 , Figure 2 In the diagram, the length direction of the secondary battery 100 is represented by x, the width direction by y, and the thickness direction by z. These directions are orthogonal to each other.

[0063] The secondary battery 100 includes a power generation element 10 and an outer casing 20 that internally houses the power generation element 10. Additionally, the secondary battery 100 includes a positive terminal 31 and a negative terminal 32 (hereinafter, sometimes collectively referred to as "electrode terminals 30") for connection to an external power source or electrical load. The positive terminal 31 and the negative terminal 32 are arranged to protrude from different surfaces in the width direction of the outer casing 20. However, the arrangement of the positive terminal 31 and the negative terminal 32 is not limited to this; they may also be arranged to protrude from the same surface in the width direction of the outer casing 20. As an example, Figure 3 The diagram shows a secondary battery in which the positive terminal 31 and the negative terminal 32 are arranged to protrude from the same side in the width direction of the outer casing 20.

[0064] <Power Generation Element 10>

[0065] The power generation element consists of 10 layers: a positive electrode current collector foil, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, and a negative electrode current collector foil (hereinafter, they are sometimes collectively referred to as "electrode elements"). The electrode elements are stacked in the thickness direction. There is no particular limitation on the number of each electrode element stacked. Figure 2 The power generation element 10 consists of multiple stacked electrode elements. Furthermore, these electrode elements can be stacked in series or in parallel.

[0066] Figure 2 The power generation element 10 has a sheet-like shape, which is rectangular when viewed from above. However, the power generation element 10 is not particularly limited as long as it has a shape that can be accommodated inside the outer casing 20. Additionally, as... Figure 2 As shown, each current collector foil of the power generation element 10 may have tabs 11 and 12 for connection to each electrode terminal 30. Tabs 11 are provided on each positive current collector foil and are electrically connected to the positive terminal 31. Similarly, tabs 12 are provided on each negative current collector foil and are electrically connected to the negative terminal 32.

[0067] To suppress short circuits caused by contact with the cylindrical portion 21, the power generation element 10 may also undergo predetermined insulation treatment. For example, the power generation element 10 may be wrapped with an insulating film, an insulating sheet may be disposed between the power generation element 10 and the cylindrical portion 21, or an insulating tape may be attached to the inner surface of the power generation element 10 or the cylindrical portion 21. In this way, an insulation treatment in which a predetermined insulating layer is disposed can be performed on the outer periphery of the power generation element 10.

[0068] Furthermore, the power generation element 10 and the cylindrical portion 23 can make contact as long as either of them is insulated. In this case, the thickness of the inner cover terminal 22 can be thinner than the thickness of the power generation element 10 by the amount of the first resin 23 filling the space between the cylindrical portion 21 and the inner cover terminal 22.

[0069] The power generation element 10 can be a solid-state battery or a liquid-state battery. A solid-state battery is preferred. Furthermore, the type of power generation element 10 is not particularly limited; it can be a power generation element used in lithium-ion secondary batteries or a power generation element used in sodium-ion secondary batteries. The materials of the power generation element for lithium-ion secondary batteries will be described below.

[0070] (Positive electrode current collector foil, negative electrode current collector foil)

[0071] The positive and negative current collector foils are sheet-like metal foils. The metals constituting the positive and negative current collector foils are not particularly limited; examples include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. Al is preferred as the metal constituting the positive current collector foil. Cu is preferred as the material constituting the negative current collector foil.

[0072] The positive and negative current collector foils may also have certain coatings (e.g., carbon coatings) on their surfaces for adjusting resistance. The thickness of the positive and negative current collector foils may be, for example, greater than 0.1 μm and less than 1 mm.

[0073] (Positive electrode active material layer)

[0074] The positive electrode active material layer is a sheet-like layer containing positive electrode active material. There are no special limitations on the positive electrode active material; it can be any material suitable for use in lithium-ion secondary batteries. Examples include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, spinel-based lithium compounds, and various lithium-containing composite oxides.

[0075] The positive electrode active material layer can arbitrarily contain conductive additives and binders. The binder can be any binder suitable for lithium-ion secondary batteries, without particular limitations. Examples include butadiene rubber (BR), butene rubber (IIR), acrylate butadiene rubber (ABR), and poly(1,1-difluoroethylene) (PVdF). The conductive additive can be any conductive additive suitable for lithium-ion secondary batteries, without particular limitations. Examples include carbon materials such as acetylene black and highly conductive carbon black, or metallic materials such as nickel, aluminum, and stainless steel.

[0076] In the case where the secondary battery 100 is an all-solid-state battery, the positive electrode active material layer can arbitrarily contain a solid electrolyte. The solid electrolyte is not particularly limited as long as it is suitable for use in lithium-ion secondary batteries. For example, it can be an organic polymer electrolyte or an inorganic solid electrolyte. An inorganic solid electrolyte is preferred because it has higher ionic conductivity and better heat resistance compared to organic polymer electrolytes. The inorganic solid electrolyte can be an oxide solid electrolyte or a sulfide solid electrolyte. A sulfide solid electrolyte is preferred. Examples of oxide solid electrolytes include lithium lanthanum zirconate, LiPON, and Li...1+X AlXGe 2-X (PO4)3, Li-SiO glass, Li-Al-SO glass, etc. Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5-GeS2.

[0077] The content of each component in the positive electrode active material layer can be appropriately set according to the purpose. Additionally, the surface of the positive electrode active material can also be covered by oxide layers such as lithium niobate, lithium titanate, or lithium phosphate. The thickness of the positive electrode active material layer can be set, for example, to be 0.1 μm or more and 1 mm or less.

[0078] (Negative electrode active material layer)

[0079] The negative electrode active material layer is a sheet-like layer containing negative electrode active material. There are no special limitations on the negative electrode active material; it can be any material suitable for use in lithium-ion secondary batteries. Examples include silicon and Si alloys, silicon-based active materials such as silicon oxide, carbon-based active materials such as graphite and hard carbon, various oxide-based active materials such as lithium titanate, and metallic lithium and lithium alloys.

[0080] The negative electrode active material layer may arbitrarily contain conductive additives and binders. The conductive additives and binders can be appropriately selected from those suitable for use in the positive electrode active material layer. Furthermore, in the case where the secondary battery 100 is an all-solid-state battery, the negative electrode active material layer may arbitrarily contain a solid electrolyte. The solid electrolyte can be appropriately selected from those suitable for use in the positive electrode active material layer.

[0081] The content of each component in the negative electrode active material layer can be appropriately set according to the purpose. The thickness of the negative electrode active material layer can be set, for example, above 0.1 μm and below 1 mm.

[0082] (Electrolyte layer)

[0083] In the case of the secondary battery 100 being an all-solid-state battery, the electrolyte layer is a sheet-like solid electrolyte layer.

[0084] The solid electrolyte layer contains a solid electrolyte. The solid electrolyte can be appropriately selected from those suitable for use in the positive electrode active material layer. Additionally, the solid electrolyte layer may arbitrarily contain a binder. The binder can be appropriately selected from those suitable for use in the positive electrode active material layer. The content of each component in the solid electrolyte layer can be appropriately set according to the purpose. The thickness of the solid electrolyte layer can be, for example, 0.1 μm or more and 1 mm or less.

[0085] In the case of a liquid-based secondary battery 100, the electrolyte layer includes an electrolyte and a separator. The electrolyte and separator can be any type suitable for lithium-ion secondary batteries and are not particularly limited. Examples of separators include porous sheets (membranes) made of polyolefins such as polyethylene (PE) and polypropylene (PP). The thickness of the separator can be, for example, 0.1 μm or more and 1 mm or less. The electrolyte typically contains a non-aqueous solvent and a supporting electrolyte. Examples of non-aqueous solvents include carbonates, ethers, esters, nitriles, sulfones, and lactones. Examples of supporting electrolytes include LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), and bis(trifluoromethyl)sulfonylimide (LiTFSI). The concentration of the supporting electrolyte in the electrolyte is not particularly limited and can be, for example, 0.5 mol / L or more and 5 mol / L or less. Additionally, any components such as gas generators, film-forming agents, dispersants, and thickeners can be added to the electrolyte.

[0086] <Exterior Design Department 20>

[0087] The outer casing 20 includes: a cylindrical portion 21 having openings 21a on two opposing surfaces; an inner cover 22 disposed on each opening 21a; and a first resin 23 disposed to cover the opening sides of each opening 21a and the inner cover 22. Furthermore, the first resin 23 is disposed to fill the space between the cylindrical portion 21 and the inner cover 22, and the cylindrical portion 21 and the inner cover 22 are integrated using the first resin 23.

[0088] (Tubular part 21)

[0089] The cylindrical portion 21 has a hollow shape with openings 21a on two opposing surfaces. The openings 21a are respectively provided on both sides of the cylindrical portion 21 along its length. The cross-sectional shape of the cylindrical portion 21 in its width direction is rectangular. However, the cross-sectional shape of the cylindrical portion is not limited to this. Figure 4 (a) shows a top view of the cylindrical portion 21, (b) shows a cross-sectional view in the width direction, and (c) shows a side view of the cylindrical portion 21 as viewed in the width direction.

[0090] From the viewpoint of preventing the deterioration of power generation elements, the cylindrical section 21 is made of a metal with high water vapor barrier properties. A metal with high water vapor barrier properties refers to, for example, a water vapor permeability of less than 1.0 × 10⁻⁶. -4 g / m 2 • Metals that can withstand 24 hours of water vapor transmission. The lower the water vapor permeability, the higher the water vapor barrier properties. Examples of such metals include aluminum, stainless steel, SUS, and duralumin. From the viewpoints of lightweight and processability, aluminum can be used as the material for the cylindrical part 21. In addition, aluminum is inexpensive.

[0091] Water vapor permeability can be determined using the cup method according to JIS Z 0208 and the gas chromatography method according to JIS K 7129.

[0092] Here, from the viewpoint of suppressing short circuits caused by contact with the power generation element 10, the cylindrical portion 21 can also be subjected to predetermined insulation treatment. For example, an insulating material such as an insulating resin sheet can be disposed between the power generation element 10 and the cylindrical portion 21. The insulating material can be disposed, for example, between the thickness direction surface of the power generation element 10 and the cylindrical portion 21. As a result, electrical connection between the power generation element 10 and the cylindrical portion 21 can be suppressed, thereby suppressing short circuits in the secondary battery 100.

[0093] Alternatively, a metal laminate (e.g., an aluminum laminate) can be used, where at least the inner surface of the cylindrical portion 21 is covered with an insulating resin. This allows for the suppression of electrical connection between the power generation element 10 and the cylindrical portion 21 without requiring an insulating material, thus preventing short circuits in the secondary battery 100. A metal laminate is a multilayer material in which a resin (e.g., polypropylene, nylon, PET, etc.) is disposed on the surface of a metal layer. This allows for insulation treatment, such as the placement of a predetermined insulating layer, on the inner periphery of the cylindrical portion 21.

[0094] However, the thickness of the metal layer in a metal laminate is typically around 0.04 mm, which is relatively thin, resulting in low strength. Therefore, the cylindrical portion 21 is preferably made of metal with a thickness of 0.05 mm or more and 0.2 mm or less, and more preferably of 0.1 mm or more and 0.2 mm or less. Alternatively, a metal laminate containing a metal layer with a thickness within the aforementioned range can also be used as the cylindrical portion 21. Furthermore, when using a metal laminate in the cylindrical portion 21, a metal laminate formed into a cylindrical shape is used.

[0095] The cylindrical portion 21 may also have a protrusion 21b at its longitudinal end. Specifically, the cylindrical portion 21 may have a protrusion 21b at at least one of its surfaces in the thickness and width directions at its longitudinal end. By providing the protrusion 21b, the adhesive force is improved by ensuring sufficient bonding area with the first resin 23. The protrusion 21b refers to the portion that protrudes outward from the inner cover 22.

[0096] Figure 5 (a) shows a cross-sectional view near the opening 21a of a cylindrical portion 21 in which protrusions 21b are provided at each end of the surface in the thickness direction. Additionally, Figure 5 (b) shows a cross-sectional view near the opening 21a of the cylindrical portion 21, which is provided with a protrusion 21b that bends inward.

[0097] Figure 5 The cylindrical portion 21 shown in (a) has protrusions 21b at each end of its thickness-direction surface. That is, the cylindrical portion 21 has a structure in which the end of its thickness-direction surface protrudes further than the end of its width-direction surface. Figure 5 As shown in (a), the cylindrical portion 21, by having a protrusion 21b, increases the bonding area between the cylindrical portion 21 and the first resin 23, thereby improving the adhesive strength. In other words, it can suppress the peeling of the first resin 23. If the first resin 23 peels off, water vapor barrier properties cannot be guaranteed, which is undesirable. Furthermore, as... Figure 5 As shown in (b), the protrusion 21b may also have a shape that bends inward toward the inside of the cylindrical portion 21. This makes positioning of the inner cover 22 easier. In this case, the opening formed from the two protrusions 21 becomes the opening 21a. The angle between the protrusion 21b and the surface of the cylindrical portion 21 (the surface with the protrusion 21b) is not specifically limited and can be any angle from 0° to 180°. Preferably, it is from 15° to 135°. The length of the protrusion 21b is not particularly limited. For example, it is in the range of 0.5 mm to 2 mm.

[0098] (Inner cover 22)

[0099] The inner cover 22 is disposed at each opening 21a of the cylindrical portion 21. The inner cover 22 has a rectangular outer peripheral shape. However, the outer peripheral shape of the inner cover 22 is not particularly limited, as long as it has a cross-sectional shape along the width direction of the cylindrical portion 21. Figure 6 (a) shows a perspective view of the inner cover 22, (b) shows a sectional view cut by bb in (a), and (c) shows a sectional view cut by cc in (a).

[0100] The inner cover 22 has a surface 22a disposed on the side of the opening 21a of the cylindrical portion 21, a protrusion 22b that protrudes integrally from the outer periphery of the surface 22a toward the inside of the cylindrical portion 21, and a space 22c surrounded by the protrusion 22b. The space 22c opens toward the inside of the cylindrical portion 21.

[0101] The "protrusion 22b, which protrudes integrally from the outer periphery of surface 22a toward the inner side of cylindrical portion 21" refers to the portion that protrudes into the inner side of cylindrical portion 21 from both ends in the thickness direction and both ends in the width direction of surface 22a, and these portions are connected at each corner of surface 22a. That is, the protrusion 22b is a component that protrudes integrally from the outer periphery of surface 22a. The length L1 of the protrusion 22b is not particularly limited, as long as it can provide sufficient water vapor barrier properties when the cylindrical portion 21 and the inner cover 22 are integrated using the first resin 23. For example, it can be set to 0.5 mm or more, or 3 mm or less.

[0102] The inner cover 22 has a through hole 22d on its surface 22a, through which an electrode terminal 30 (positive terminal 31 or negative terminal 32) passes. Figure 1 When the electrode terminals 30 are arranged on different surfaces in the width direction of the outer casing 20, the inner cover 22 has a through hole 22d in each case. On the other hand, in cases such as Figure 3 When the electrode terminals 30 are arranged on the same side of the outer casing 20 in the width direction, it is sufficient to provide a through hole 22d in at least one inner cover 22 (the inner cover 22 on the side where the electrode terminals 30 are arranged). In this case, the number of through holes 22d can also be provided in such a way that each electrode terminal 30 is arranged in two. Alternatively, each electrode terminal 30 can be arranged in one through hole 22d.

[0103] The inner cover 22 can be composed of one component or two or more components. From the viewpoint of facilitating the placement of the electrode terminals 30, the inner cover 22 can be composed of two components whose length in the thickness direction is divided in such a way as to include a through hole 22c. Alternatively, the inner cover 22 may have a tapered portion 22e between the surface 22a and the protrusion 22b. As an example, Figure 7 (a) shows a cross-sectional view of the inner cover 22 with a tapered portion 22e, and (b) shows an example of the use of the inner cover 22 with a tapered portion 22e.

[0104] From the perspective of preventing the deterioration of power generation elements, the inner cover 22 can be made of a material with high water vapor barrier properties. A material with high water vapor barrier properties refers to, for example, a water vapor permeability of less than 1.0 × 10⁻⁶. -4 g / m 2• 24h material. Such materials include, for example, metal or glass. From a processability point of view, metal can be used as the material for the inner cover 22. Examples of metals include aluminum, stainless steel, SUS, and duralumin. From the viewpoints of lightweight and processability, aluminum can be used as the material for the inner cover 22. In addition, aluminum is inexpensive.

[0105] Here, when the inner cover 22 is made of metal, from the viewpoint of suppressing short circuits caused by contact between the inner cover 22 and the power generation element 10, the cylindrical portion 21, and the electrode terminal 30, a predetermined insulation treatment can be performed. For example, from the viewpoint of suppressing short circuits caused by contact with the power generation element 10, an insulating material such as an insulating resin sheet can be disposed between the inner cover 22 and the power generation element 10. This can suppress electrical connection between the power generation element 10 and the inner cover 22, thereby suppressing short circuits in the secondary battery 100. In addition, from the viewpoint of suppressing short circuits caused by contact between the inner cover 22 and the cylindrical portion 21, a laminated metal in which at least the inner surface of the cylindrical portion 21 is covered with an insulating resin can be used. This can suppress electrical connection between the power generation element 10 and the cylindrical portion 21 without the need for an insulating material, thereby suppressing short circuits in the secondary battery 100. Furthermore, in order to suppress short circuits caused by contact with the cylindrical portion 21, the outer periphery of the inner cover 22 can be wrapped with an insulating film, and an insulating tape can be attached to the outer periphery of the inner cover 22. In this way, an insulation treatment with a predetermined insulating layer can be performed on the outer periphery of the inner cover 22. Furthermore, in order to suppress short circuits caused by contact between the inner cover 22 and the electrode terminal 30, an insulation treatment with a predetermined insulating layer can also be performed on either the through hole 22d or the electrode terminal 30.

[0106] (Resin 1, 23)

[0107] The first resin 23 is disposed to cover the openings 21a and the opening-side surface 22a of the inner cover 22. Furthermore, the first resin 23 is disposed to fill the space between the cylindrical portion 21 and the inner cover 22, thus integrating the cylindrical portion 21 and the inner cover 22 using the first resin 23. When the inner cover 22 is provided with electrode terminals 30, the first resin 23 is also disposed to cover at least a portion of the outer periphery of the electrode terminals 30 and fill the space between the through hole 22d and the electrode terminals 30. Moreover, the cylindrical portion 21, the inner cover 22, and the electrode terminals are integrated using the first resin 23. Therefore, the secondary battery 100 can ensure sufficient water vapor barrier properties.

[0108] like Figure 2 As shown, the first resin 23 covers the opening 21a and the surface 22a on the side of the opening 21a of the inner cover 22, and also fills the gap between the cylindrical part 21 and the inner cover 22.

[0109] "The gap between the cylindrical portion 21 and the inner cover 22" refers to the gap between the inner surface of the cylindrical portion 21 and the outer periphery of the inner cover 22. The opening 21a covered by the first resin 23 refers to the surface on the side of the opening 21a of this gap. To form such a gap, the inner cover 22 is preferably made to be slightly smaller than the outer shape of the cylindrical portion 21. By configuring the first resin 23 as described above, the cylindrical portion 21 and the inner cover 22 are integrated using the first resin 23. Here, the first resin 23 only needs to fill at least a portion of the gap between the cylindrical portion 21 and the inner cover 22, but from the viewpoint of ensuring water vapor barrier properties, it is preferable to fill the gap as described above. Figure 2 That way, the gap is filled as a whole. However, if the second resin 24 is filled inside the cylindrical part 21 as described later, the second resin 24 may also be disposed in addition to the first resin 23 in the gap formed by the cylindrical part 21 and the inner cover 22.

[0110] Furthermore, the first resin 23 covers at least a portion of the outer periphery of the electrode terminal 30, filling the gap between the electrode terminal 30 and the through hole 22d. "At least a portion of the outer periphery of the electrode terminal 30" refers to the outer periphery of a region of the electrode terminal 30 extending outward from surface 22a by a predetermined length. The predetermined length refers to... Figure 2 The length L2. "The gap existing between the electrode terminal 30 and the through hole 22d" refers to the gap existing between the outer periphery of the electrode terminal 30 and the inner surface of the through hole 22d. To form such a gap, it is preferable to make the through hole 22d larger than the electrode terminal 30. By configuring the first resin 23 as described above, the inner cover 22 and the electrode terminal 30 are integrated using the first resin 23.

[0111] In this way, the outer casing 20 fills the path (gap) through which water vapor can penetrate from the outside to the inside with the first resin 23, thus effectively suppressing the intrusion of water vapor into the interior of the outer casing 20. In other words, this means that there can also be gaps between the cylindrical portion 21 and the inner cover 22, and between the electrode terminal 30 and the through hole 22, allowing water vapor to penetrate. Since such gaps are filled with the first resin 23, the cylindrical portion 21 and the inner cover 22 do not need to be designed to be airtight.

[0112] Here, "integration" means that the various materials are bonded together with resin to the extent that they can be identified as a single component. By placing the cylindrical portion 21, which houses the power generation element 10, and the intermediate component, in which an inner cover 22 is disposed at the opening 21a of the cylindrical portion 21, in a predetermined mold, injecting the first resin into the mold, and allowing the first resin to cure, "integration" achieved by the first resin can be realized. In this way, the outer casing 20 can be manufactured by integral molding using the first resin 23.

[0113] Here, as Figure 7 As shown in (b), when the inner cover 22 has a conical portion 22e, the first resin 23 enters between the conical portion 22e and the cylindrical portion 21. Therefore, the bonding area between the first resin 23 and the inner cover 22 can be increased, and the bonding strength of these components can be improved.

[0114] The length L2 from the end of the first resin 23 to the opening side of the inner cover 22 is not particularly limited, but it can be set to 0.5 mm or more, or 2 mm or less, taking into account water vapor barrier properties.

[0115] In this way, the secondary battery 100 uses the outer casing 20 instead of the conventional laminated casing to seal the power generation element 10, thereby providing water vapor barrier properties equal to or better than those of conventional laminated casings. Furthermore, in conventional laminated casings, when the ends are heat-fused after housing the power generation element, sealing defects sometimes occur. In such cases, water vapor may infiltrate from the poorly sealed areas, thus compromising water vapor barrier properties. In contrast, the secondary battery 100 uses the first resin 23 to seal the power generation element 10 inside the outer casing 20, making sealing defects very difficult to occur. Therefore, water vapor barrier property checks (leakage checks) can be omitted after manufacturing the secondary battery 100.

[0116] Resin 23, from the viewpoint of preventing the deterioration of power generation elements, uses a resin with water vapor barrier properties. A resin with water vapor barrier properties refers to, for example, a water vapor permeability of 1.0 × 10⁻⁶. -4 g / m 2 ·More than 24 hours and 50×10 -4 g / m 2 • Resins with a shelf life of 24 hours or less. There is no particular limitation on the type of resin; thermoplastic resins are an example. Examples of thermoplastic resins include polypropylene and polyester.

[0117] <Electrode terminal 30>

[0118] The electrode terminal 30 has a positive terminal 31 and a negative terminal 32, which are electrically connected to the power generation element 10. Specifically, the positive terminal 31 is electrically connected to the positive current collector foil (tab 11), and the negative terminal 32 is electrically connected to the negative current collector foil (tab 12). The connection method is not particularly limited; for example, ultrasonic waves can be used to connect the electrode terminal to the current collector foil.

[0119] The electrode terminal 30 is arranged as described above in a through hole 22d that penetrates the inner cover 22, and protrudes outward from the opening 21a. Furthermore, the first resin 23 covers at least a portion of the outer periphery of the electrode terminal 30 and fills the gap between the electrode terminal 30 and the through hole 21, thereby integrating the inner cover 22 and the electrode terminal using the first resin 23.

[0120] The material of the electrode terminal 30 is not particularly limited and can be appropriately selected from any metal that can be used for current collector foil.

[0121] <Constructing High Efficiency>

[0122] Next, the high efficiency of the secondary battery 100 will be explained. Figure 8 , Figure 9 The figure shows a comparison between a conventional laminated battery and a secondary battery 100. Figure 8 This is a diagram comparing the longitudinal cross-sectional view of a conventional laminated battery (a) with that of a secondary battery 100 (b). Figure 9 This diagram compares a conventional laminated battery (a) with a secondary battery 100 (b) from top view.

[0123] like Figure 8 As described in (a), conventional laminated batteries have a terminal portion (region A) protruding from the laminated outer casing, a heat-fusion portion (region B) where the laminated outer casing is heat-fused, a joint portion (region C) where the electrode terminals are joined to the current collector foil, and a current collector foil portion (region D) where multiple current collector foils connected to the power generation element are located.

[0124] like Figure 8 As shown in (b), in the secondary battery 100, the length of the portions corresponding to regions A and D is the same as that of a conventional laminated battery. On the other hand, by using the outer casing 20, the secondary battery 100 can have a shorter length than that of the portions corresponding to regions B and C compared to a conventional laminated battery. Details are as follows.

[0125] First, the reason for the shortening of the length corresponding to region B will be explained. In the past, the length of region B (sealing width) of laminated batteries was usually set to be more than 3 mm. This is due to the following reasons: (1) If the sealing width is short, proper heat fusion cannot be performed, resulting in poor sealing. (2) Since the rigidity of the laminated outer casing is not high, if the sealing width is short, the adhesive in the sealing area will peel off due to external impacts, resulting in the adhesive surface not being able to be maintained.

[0126] (3) During heat fusion welding, if the bonding surface of the terminal is not parallel to the laminated outer casing, a short sealing width weakens the corrective force to restore its tilt, thus increasing the probability of inadequate heat fusion welding and poor sealing. (4) During heat fusion welding, a short sealing width increases the pressure per unit area applied by the heat fusion joint to the sealing area, potentially causing the metal layer inside the laminated outer casing to penetrate the insulation layer and bite into the terminal. If the metal layer bites into the terminal, it will cause a short circuit, which is undesirable.

[0127] On the other hand, in the secondary battery 100, an outer casing 20 is used where the cylindrical portion 21 and the inner cover 22 are integrated using a first resin 23. This integration using the first resin 23 effectively suppresses poor adhesion between the cylindrical portion 21 and the inner cover 22. Furthermore, even when the inner cover 22 is tilted or the gap between the cylindrical portion 21 and the inner cover 22 is not parallel, proper adhesion can still be achieved. Moreover, since no heat welding is performed, short circuits are virtually nonexistent. Furthermore, the integration using the first resin 23 ensures rigidity, thus suppressing peeling of the adhesive portion. Therefore, the secondary battery 100 can have a length (L1+L2) of the portion corresponding to region B in a conventional laminated battery set to 3 mm or less. Alternatively, it can be 2 mm or less. Therefore, compared to a conventional laminated battery, the secondary battery 100 can shorten the width of the portion corresponding to region B.

[0128] Next, the reason why the length of the part corresponding to region C is shorter will be explained. For example... Figure 8 As shown, the inner cover 22 of the secondary battery 100 has a space 22c inside the protrusion 22b, in which the electrode terminal 30 is joined to the current collector foil. In this way, the secondary battery 100 can effectively utilize the space 22c of the inner cover 22. Therefore, in the secondary battery 100, the length of the portion corresponding to region C can be shortened visually. Furthermore, as... Figure 8 As shown in (b), the secondary battery 100 can also utilize one region to perform the functions of regions B and C. Therefore, compared with conventional laminated batteries, the secondary battery 100 can achieve a more efficient structure.

[0129] Next, regarding Figure 9 Please provide an explanation. For example... Figure 9 As shown, conventional laminated batteries require heat-sealed sections S on the four outermost sides. In contrast, the two ends of the secondary battery 100 in the length direction achieve high structural efficiency through the outer casing 20 as described above. Furthermore, since the secondary battery 100 uses a cylindrical metal body, namely the cylindrical section 21, heat-sealed sections are not required on both sides in the width direction. Therefore, the secondary battery 100 achieves high structural efficiency in this respect. In addition, the absence of heat-sealed sections on both sides in the width direction also improves water vapor barrier properties.

[0130] As mentioned above, the secondary battery 100 has a significantly improved construction efficiency compared to conventional laminated batteries.

[0131] Here, the advantages of the secondary battery 100 compared to a secondary battery that uses a laminated outer casing and an inner cover to seal the power generation element will be explained. It is also believed that by placing the inner cover at the opening of the cylindrical laminated outer casing and heat-sealing the outer peripheral surfaces of the laminated outer casing and the inner cover, a more efficient secondary battery structure can be achieved compared to conventional laminated batteries. This is because the internal space of the inner cover can be utilized. However, since the laminated outer casing and the inner cover are bonded using heat fusion, it is difficult to achieve a sealing width of less than 3 mm. Specifically, this is due to the following reasons.

[0132] (1) If the sealing width is short, there is a possibility of poor sealing. (2) Since the rigidity of the laminated outer casing is not high, if the sealing width is short, the adhesive in the sealing area may peel off due to external impact, and the adhesive surface may not be maintained. (3) In addition, when the inner cover tilts due to external impact, the corrective force to restore its tilt is weakened, so the adhesive surface may not be properly maintained. (4) During heat welding, if the outer peripheral surface of the inner cover is not parallel to the welding surface of the laminated outer casing, if the sealing width is short, the corrective force to restore its tilt is weakened, so the probability of poor sealing is higher. In addition, if the laminated outer casing is formed into a cylindrical shape, there may be areas that need to be sealed on the side. For the above reasons, the secondary battery 100 has improved construction efficiency even compared with a secondary battery obtained by combining a laminated outer casing and an inner cover.

[0133] Furthermore, there are manufacturing advantages. When heat-welding the outer periphery of the laminated outer casing and the inner cover, the inner cover cannot be controlled from the inside, resulting in difficulties in heat welding. On the other hand, the secondary battery 100 can integrate these components by placing the cylindrical portion 21 and the inner cover 22 in a predetermined mold and filling them with the first resin 23, thus avoiding this problem. In addition, since the power generation element 10 is housed in the cylindrical portion 21 and integrated using a predetermined mold, the assemblability of each component is better and the dimensional accuracy is better compared to the case of using a laminated outer casing.

[0134] <Short-circuit suppression of power generation element 10 and external assembly 20>

[0135] When the cylindrical portion 21 and the inner cover 22 are made of metal, from the viewpoint of suppressing short circuits caused by contact between the power generation element 10 and these components, as described above, an insulating material may be disposed between the power generation element 10 and these components. The specific form of the insulating material disposed will be described below.

[0136] First, the secondary battery 101, in which the second resin 24 is filled inside the outer casing 20, will be described. Figure 10The image shows a cross-sectional view along the length of a secondary battery 101 whose interior is entirely filled with a second resin 24.

[0137] like Figure 10 As shown, the outer casing 20 includes a second resin 24 filled therein. The second resin 24 can be the same resin as the first resin 23. Figure 10 In this configuration, the second resin 24 is disposed throughout the interior of the outer casing 20, but is not limited thereto, as long as it is disposed at a position where the power generation element 10 can contact the outer casing 20. Preferably, the second resin 24 is disposed throughout the interior of the outer casing 20.

[0138] In this way, by providing the second resin 24 inside the outer casing 20, the cylindrical portion 21, the inner cover 22, the electrode terminals 30, and the power generation element 10 can be integrated using the second resin 24. This suppresses short circuits caused by contact between the power generation element 10 and the outer casing 20. For example, even if the power generation element 10 or the outer casing 20 is provided with a predetermined insulating layer, a short circuit may occur if the insulating layer breaks due to an external impact, causing contact between the power generation element 10 and the outer casing 20. In contrast, by providing the second resin 24 inside the outer casing 20, contact between the power generation element 10 and the outer casing 20 can be more effectively suppressed compared to the case where only an insulating layer is provided, thus preventing battery short circuits.

[0139] Furthermore, the secondary battery 100, by incorporating the second resin 24, can further improve its water vapor barrier properties. Moreover, by integrating all components using the second resin 24, movement of the power generation element 10 due to external impacts can be suppressed, thus preventing the current collector foil and / or tabs 11, 12 from being cut due to movement of the power generation element 10. In addition, damage and / or slippage of the power generation element 10 due to external impacts can also be suppressed.

[0140] The method for filling the interior of the outer part 20 with the second resin 24 is not particularly limited. For example, holes for injecting the second resin 24 can be provided at predetermined locations in the cylindrical part 21 and / or the inner cover 22. The shape of the holes is not particularly limited; they can be circular, elliptical, or rectangular. At least one hole can be provided in the cylindrical part 21, and at least one hole can be provided in the inner cover 22. For example, as... Figure 4 As shown in (c), multiple holes 21c and 21d of different shapes can be provided on the side of the cylindrical portion 21. Alternatively, as shown in [the diagram]... Figure 6 As shown in (a), a plurality of holes 22f are provided on the surface 22a of the inner cover 22. Furthermore, in the case of a power generation element using a liquid battery as a power generation element, after filling the second resin 24, a predetermined electrolyte can be injected through the holes.

[0141] Next, the secondary battery 102, in which the power generation element 10 is wrapped with a resin film 13 that has insulating and water vapor barrier properties, will be described. Figure 11 The image shows a cross-sectional view along the length of a secondary battery 102 in which the power generation element 10 is wrapped by a resin film 13. Figure 12 The image shows a top view of the power generation element 10 encased in a resin film 13.

[0142] like Figure 11 , Figure 12 As shown, the resin film 13 has a cylindrical shape and an opening on the side where the electrode terminals 30 are disposed. Furthermore, the resin film 13 completely encapsulates the power generation element 10. Figure 12 In the diagram, components disposed within the resin membrane 13 are shown in dashed lines. Besides enclosing the power generation element 10, the resin membrane 13 may also enclose at least a portion of the electrode terminals 30. For example, as... Figure 11 As shown, alternatively, the end of the resin film 13 can wrap around the electrode terminal 30 disposed inside the first resin 23 through the through hole 22d of the inner cover 22. This allows the resin film 13 to be fixed using the first resin 23. By completely wrapping the power generation element 10 with the resin film 13 in this way, short circuits caused by contact between the power generation element 10 and the outer casing 20 can be suppressed. Furthermore, by including the resin film 13, the secondary battery 100 can further improve its water vapor barrier properties.

[0143] The resin film 13 can be any resin film that has insulating and water vapor barrier properties. For example, resin films coated with aluminum or silica can be used. There are no particular limitations on the type of resin; for example, polypropylene and polyethylene terephthalate can be used.

[0144] Alternatively, the power generation element 10 can be wrapped with a resin film 13 and the second resin 24 can be filled inside the outer casing 20.

[0145] Other forms of the tubular portion

[0146] From the perspective of efficient construction, the cylindrical part 21, such as Figure 3 As shown, it can be a cylindrical metal body or a metal laminate formed into a cylindrical shape. A cylindrical metal body is preferred. On the other hand, in such a cylindrical part, there is a problem that it is difficult to house the power generation element 10 inside. Therefore, the following cylindrical parts 121 and 221, which are easy to house the power generation element 10, can also be used.

[0147] First, the cylindrical portion 121 will be explained. Figure 13 (a) shows a top view of the cylindrical portion 121, and (b) shows a cross-sectional view of the cylindrical portion 121 in the width direction. Figure 13As shown, the cylindrical portion 121 is composed of two metal plates 121a and a third resin 121d. The metal plate 121a is a so-called U-shaped component having a bottom surface 121b and protrusions 121c extending in the same direction from opposite ends of the bottom surface 121b. Figure 13 As shown in (b), two metal plates 121a are overlapped in an inverted manner, and protrusions 121c of the two metal plates 121a are overlapped on opposite sides (width direction) of the cylindrical portion 121. Furthermore, a third resin 121c is disposed to cover each side of the cylindrical portion 121. Specifically, the third resin 121c completely covers the side surfaces of the protrusions 121c of the overlapping metal plates 121a and fills the gaps between the protrusions 121c of the overlapping metal plates 121a. Thus, the ends of the overlapping metal plates 121a are integrated using the third resin 121c.

[0148] The cylindrical portion 121 has two metal plates 121a. Therefore, after the power generation element 10 is disposed inside one of the metal plates 121a, the other metal plate 121a is inverted and overlapped, and the protrusions 121c of the metal plates 121a are integrated using a third resin 121d, thereby making the cylindrical portion 121. In this way, by using the cylindrical portion 121, the power generation element 10 can be easily housed inside the cylindrical portion 121.

[0149] Next, the cylindrical portion 221 will be described. Figure 14 (a) shows a top view of the cylindrical portion 221, and (b) shows a cross-sectional view of the cylindrical portion 221 in the width direction. Figure 14 As shown, the cylindrical portion 221 is composed of a metal plate 221a and a third resin 221d. The metal plate 221a is formed into a cylindrical shape, and an end portion 221b of the metal plate 221a overlaps on one side of the cylindrical portion 221. Furthermore, the third resin 221c is arranged to cover the overlapping side of the end portion 221b. Specifically, the third resin 221c completely covers the side of the overlapping end portion 221b and fills the gaps in the end portion 221b of the overlapping metal plate 221a. Thus, the end portion 221b of the overlapping metal plate 221a is integrated using the third resin 221c.

[0150] The cylindrical portion 221 is constructed from a single metal plate 121a. Therefore, after placing the power-generating element 10 inside the cylindrical metal plate 221a, the cylindrical portion 221 can be manufactured by integrating the end 221b with a third resin 121c. In this way, the power-generating element 10 can be easily housed inside the cylindrical portion 221. Furthermore, as... Figure 15As shown, by bringing the side of the cylindrical portion 221 without the third resin 221c into contact with the predetermined cooling portion X, the secondary battery can be easily cooled. Furthermore, this cooling method can also be applied to secondary batteries that use the cylindrical portion 21.

[0151] The metal sheet used in the above two methods can be a simple metal sheet or a metal laminate. A metal sheet is preferred. The type of metal can be one with high water vapor barrier properties. The third resin used in the above two methods can be the same resin as the first resin 23. Furthermore, by placing the overlapping metal sheet 121a or the cylindrical metal sheet 221a in a predetermined mold, applying the third resin to the mold, and curing the third resin, "integration" achieved by the third resin can be realized. Thus, cylindrical portions 121 and 221 can be manufactured.

[0152] The above description of the secondary battery of this disclosure primarily uses a secondary battery 100 as one embodiment. As described above, the secondary battery of this disclosure achieves high efficiency in its construction. The secondary battery of this disclosure can be used for any application. For example, the secondary battery of this disclosure can be used as a vehicle secondary battery.

Claims

1. A secondary battery, It has a power generation element and an external assembly that internally houses the power generation element. The outer casing includes: a cylindrical portion having openings on two opposing sides, an inner cover disposed at each of the openings, and a first resin disposed to cover the opening sides of each of the openings and the inner cover. The first resin filler exists in the gap between the cylindrical portion and the inner cover. The gap between the cylindrical portion and the inner cover refers to the gap between the inner surface of the cylindrical portion and the outer periphery of the inner cover. The cylindrical portion and the inner cover are integrated using the first resin. The inner cover has a surface disposed on the opening side of the cylindrical portion, a protrusion that extends from the outer periphery of the surface toward the inner side of the cylindrical portion, and a space surrounded by the protrusion, the space opening toward the inner side of the cylindrical portion, and in the space, an electrode terminal is engaged with a current collector foil, thereby shortening the length of the portion corresponding to the engagement where the electrode terminal and the current collector foil are engaged.

2. The secondary battery according to claim 1, Equipped with electrode terminals that are connected to the power generation element. At least one of the inner covers has a through hole on the surface. The electrode terminals are arranged to pass through the through hole. The first resin disposed on the inner cover side through which the electrode terminal passes is also disposed in such a manner that it covers at least a portion of the outer periphery of the electrode terminal and fills the space between the through hole and the electrode terminal. The cylindrical portion, the inner cover, and the electrode terminals are integrated using the first resin.

3. The secondary battery according to claim 1 or 2, The outer casing has a second resin filling its interior. The cylindrical portion, the inner cover, the electrode terminals, and the power generation elements are integrated using the second resin.

4. The secondary battery according to claim 1 or 2, The power generation element is encapsulated in a resin film that has insulating and water vapor barrier properties.

5. The secondary battery according to claim 1 or 2, The cylindrical part is a cylindrical metal body or a metal laminate formed into a cylindrical shape.

6. The secondary battery according to claim 1 or 2, The cylindrical section is composed of two metal plates and a third type of resin. The metal plate has a bottom surface and protrusions extending in the same direction from opposite ends of the bottom surface. The metal plates are stacked upside down. The protrusions overlap on opposite sides of the cylindrical portion. The third resin is arranged to cover each side of the cylindrical portion. The ends of the overlapping metal plates are integrated using the third resin.

7. The secondary battery according to claim 1 or 2, The cylindrical section is composed of a metal plate and a third type of resin. The metal plate is formed into a cylindrical shape. On one side of the cylindrical portion, the end of the metal plate overlaps. The third resin is configured to cover the sides that overlap at the ends. The ends of the overlapping metal plates are integrated using the third resin.

8. The secondary battery according to claim 1 or 2, The first resin filling exists integrally in the gap between the cylindrical portion and the inner cover.

Images